Op 2021-03-11 om 18:24 schreef Thomas Hellström (Intel):
>
> Hi, Maarten,
>
> On 3/11/21 2:41 PM, Maarten Lankhorst wrote:
>> Instead of doing what we do currently, which will never work with
>> PROVE_LOCKING, do the same as AMD does, and something similar to
>> relocation slowpath. When all locks are dropped, we acquire the
>> pages for pinning. When the locks are taken, we transfer those
>> pages in .get_pages() to the bo. As a final check before installing
>> the fences, we ensure that the mmu notifier was not called; if it is,
>> we return -EAGAIN to userspace to signal it has to start over.
>>
>> Changes since v1:
>> - Unbinding is done in submit_init only. submit_begin() removed.
>> - MMU_NOTFIER -> MMU_NOTIFIER
>> Changes since v2:
>> - Make i915->mm.notifier a spinlock.
>> Changes since v3:
>> - Add WARN_ON if there are any page references left, should have been 0.
>> - Return 0 on success in submit_init(), bug from spinlock conversion.
>> - Release pvec outside of notifier_lock (Thomas).
>> Changes since v4:
>> - Mention why we're clearing eb->[i + 1].vma in the code. (Thomas)
>> - Actually check all invalidations in eb_move_to_gpu. (Thomas)
>> - Do not wait when process is exiting to fix gem_ctx_persistence.userptr.
>> Changes since v5:
>> - Clarify why check on PF_EXITING is (temporarily) required.
>> Changes since v6:
>> - Ensure userptr validity is checked in set_domain through a special path.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
>> Acked-by: Dave Airlie <airlied@xxxxxxxxxx>
>
> Mostly LGTM. Comments / suggestions below.
>
>> ---
>> drivers/gpu/drm/i915/gem/i915_gem_domain.c | 18 +-
>> .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 101 ++-
>> drivers/gpu/drm/i915/gem/i915_gem_object.h | 38 +-
>> .../gpu/drm/i915/gem/i915_gem_object_types.h | 10 +-
>> drivers/gpu/drm/i915/gem/i915_gem_pages.c | 2 +-
>> drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 796 ++++++------------
>> drivers/gpu/drm/i915/i915_drv.h | 9 +-
>> drivers/gpu/drm/i915/i915_gem.c | 5 +-
>> 8 files changed, 395 insertions(+), 584 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
>> index 2f4980bf742e..76cb9f5c66aa 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
>> @@ -468,14 +468,28 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
>> if (!obj)
>> return -ENOENT;
>>
>> + if (i915_gem_object_is_userptr(obj)) {
>> + /*
>> + * Try to grab userptr pages, iris uses set_domain to check
>> + * userptr validity
>> + */
>> + err = i915_gem_object_userptr_validate(obj);
>> + if (!err)
>> + err = i915_gem_object_wait(obj,
>> + I915_WAIT_INTERRUPTIBLE |
>> + I915_WAIT_PRIORITY |
>> + (write_domain ? I915_WAIT_ALL : 0),
>> + MAX_SCHEDULE_TIMEOUT);
>> + goto out;
>> + }
>> +
>> /*
>> * Proxy objects do not control access to the backing storage, ergo
>> * they cannot be used as a means to manipulate the cache domain
>> * tracking for that backing storage. The proxy object is always
>> * considered to be outside of any cache domain.
>> */
>> - if (i915_gem_object_is_proxy(obj) &&
>> - !i915_gem_object_is_userptr(obj)) {
>> + if (i915_gem_object_is_proxy(obj)) {
>> err = -ENXIO;
>> goto out;
>> }
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> index c72440c10876..64d0e5fccece 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> @@ -53,14 +53,16 @@ enum {
>> /* __EXEC_OBJECT_NO_RESERVE is BIT(31), defined in i915_vma.h */
>> #define __EXEC_OBJECT_HAS_PIN BIT(30)
>> #define __EXEC_OBJECT_HAS_FENCE BIT(29)
>> -#define __EXEC_OBJECT_NEEDS_MAP BIT(28)
>> -#define __EXEC_OBJECT_NEEDS_BIAS BIT(27)
>> -#define __EXEC_OBJECT_INTERNAL_FLAGS (~0u << 27) /* all of the above + */
>> +#define __EXEC_OBJECT_USERPTR_INIT BIT(28)
>> +#define __EXEC_OBJECT_NEEDS_MAP BIT(27)
>> +#define __EXEC_OBJECT_NEEDS_BIAS BIT(26)
>> +#define __EXEC_OBJECT_INTERNAL_FLAGS (~0u << 26) /* all of the above + */
>> #define __EXEC_OBJECT_RESERVED (__EXEC_OBJECT_HAS_PIN | __EXEC_OBJECT_HAS_FENCE)
>>
>> #define __EXEC_HAS_RELOC BIT(31)
>> #define __EXEC_ENGINE_PINNED BIT(30)
>> -#define __EXEC_INTERNAL_FLAGS (~0u << 30)
>> +#define __EXEC_USERPTR_USED BIT(29)
>> +#define __EXEC_INTERNAL_FLAGS (~0u << 29)
>> #define UPDATE PIN_OFFSET_FIXED
>>
>> #define BATCH_OFFSET_BIAS (256*1024)
>> @@ -864,6 +866,26 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
>> }
>>
>> eb_add_vma(eb, i, batch, vma);
>> +
>> + if (i915_gem_object_is_userptr(vma->obj)) {
>> + err = i915_gem_object_userptr_submit_init(vma->obj);
>> + if (err) {
>> + if (i + 1 < eb->buffer_count) {
>> + /*
>> + * Execbuffer code expects last vma entry to be NULL,
>> + * since we already initialized this entry,
>> + * set the next value to NULL or we mess up
>> + * cleanup handling.
>> + */
>> + eb->vma[i + 1].vma = NULL;
>> + }
>> +
>> + return err;
>> + }
>> +
>> + eb->vma[i].flags |= __EXEC_OBJECT_USERPTR_INIT;
>> + eb->args->flags |= __EXEC_USERPTR_USED;
>> + }
>> }
>>
>> if (unlikely(eb->batch->flags & EXEC_OBJECT_WRITE)) {
>> @@ -965,7 +987,7 @@ eb_get_vma(const struct i915_execbuffer *eb, unsigned long handle)
>> }
>> }
>>
>> -static void eb_release_vmas(struct i915_execbuffer *eb, bool final)
>> +static void eb_release_vmas(struct i915_execbuffer *eb, bool final, bool release_userptr)
>> {
>> const unsigned int count = eb->buffer_count;
>> unsigned int i;
>> @@ -979,6 +1001,11 @@ static void eb_release_vmas(struct i915_execbuffer *eb, bool final)
>>
>> eb_unreserve_vma(ev);
>>
>> + if (release_userptr && ev->flags & __EXEC_OBJECT_USERPTR_INIT) {
>> + ev->flags &= ~__EXEC_OBJECT_USERPTR_INIT;
>> + i915_gem_object_userptr_submit_fini(vma->obj);
>> + }
>> +
>> if (final)
>> i915_vma_put(vma);
>> }
>> @@ -1909,6 +1936,31 @@ static int eb_prefault_relocations(const struct i915_execbuffer *eb)
>> return 0;
>> }
>>
>> +static int eb_reinit_userptr(struct i915_execbuffer *eb)
>> +{
>> + const unsigned int count = eb->buffer_count;
>> + unsigned int i;
>> + int ret;
>> +
>> + if (likely(!(eb->args->flags & __EXEC_USERPTR_USED)))
>> + return 0;
>> +
>> + for (i = 0; i < count; i++) {
>> + struct eb_vma *ev = &eb->vma[i];
>> +
>> + if (!i915_gem_object_is_userptr(ev->vma->obj))
>> + continue;
>> +
>> + ret = i915_gem_object_userptr_submit_init(ev->vma->obj);
>> + if (ret)
>> + return ret;
>> +
>> + ev->flags |= __EXEC_OBJECT_USERPTR_INIT;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> static noinline int eb_relocate_parse_slow(struct i915_execbuffer *eb,
>> struct i915_request *rq)
>> {
>> @@ -1923,7 +1975,7 @@ static noinline int eb_relocate_parse_slow(struct i915_execbuffer *eb,
>> }
>>
>> /* We may process another execbuffer during the unlock... */
>> - eb_release_vmas(eb, false);
>> + eb_release_vmas(eb, false, true);
>> i915_gem_ww_ctx_fini(&eb->ww);
>>
>> if (rq) {
>> @@ -1964,10 +2016,8 @@ static noinline int eb_relocate_parse_slow(struct i915_execbuffer *eb,
>> err = 0;
>> }
>>
>> -#ifdef CONFIG_MMU_NOTIFIER
>> if (!err)
>> - flush_workqueue(eb->i915->mm.userptr_wq);
>> -#endif
>> + err = eb_reinit_userptr(eb);
>>
>> err_relock:
>> i915_gem_ww_ctx_init(&eb->ww, true);
>> @@ -2029,7 +2079,7 @@ static noinline int eb_relocate_parse_slow(struct i915_execbuffer *eb,
>>
>> err:
>> if (err == -EDEADLK) {
>> - eb_release_vmas(eb, false);
>> + eb_release_vmas(eb, false, false);
>> err = i915_gem_ww_ctx_backoff(&eb->ww);
>> if (!err)
>> goto repeat_validate;
>> @@ -2126,7 +2176,7 @@ static int eb_relocate_parse(struct i915_execbuffer *eb)
>>
>> err:
>> if (err == -EDEADLK) {
>> - eb_release_vmas(eb, false);
>> + eb_release_vmas(eb, false, false);
>> err = i915_gem_ww_ctx_backoff(&eb->ww);
>> if (!err)
>> goto retry;
>> @@ -2201,6 +2251,30 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
>> flags | __EXEC_OBJECT_NO_RESERVE);
>> }
>>
>> +#ifdef CONFIG_MMU_NOTIFIER
>> + if (!err && (eb->args->flags & __EXEC_USERPTR_USED)) {
>> + spin_lock(&eb->i915->mm.notifier_lock);
>> +
>> + /*
>> + * count is always at least 1, otherwise __EXEC_USERPTR_USED
>> + * could not have been set
>> + */
>> + for (i = 0; i < count; i++) {
>> + struct eb_vma *ev = &eb->vma[i];
>> + struct drm_i915_gem_object *obj = ev->vma->obj;
>> +
>> + if (!i915_gem_object_is_userptr(obj))
>> + continue;
>> +
>> + err = i915_gem_object_userptr_submit_done(obj);
>> + if (err)
>> + break;
>> + }
>> +
>> + spin_unlock(&eb->i915->mm.notifier_lock);
>> + }
>> +#endif
>> +
>> if (unlikely(err))
>> goto err_skip;
>>
>> @@ -3345,7 +3419,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
>>
>> err = eb_lookup_vmas(&eb);
>> if (err) {
>> - eb_release_vmas(&eb, true);
>> + eb_release_vmas(&eb, true, true);
>> goto err_engine;
>> }
>>
>> @@ -3417,6 +3491,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
>>
>> trace_i915_request_queue(eb.request, eb.batch_flags);
>> err = eb_submit(&eb, batch);
>> +
>> err_request:
>> i915_request_get(eb.request);
>> err = eb_request_add(&eb, err);
>> @@ -3437,7 +3512,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
>> i915_request_put(eb.request);
>>
>> err_vma:
>> - eb_release_vmas(&eb, true);
>> + eb_release_vmas(&eb, true, true);
>> if (eb.trampoline)
>> i915_vma_unpin(eb.trampoline);
>> WARN_ON(err == -EDEADLK);
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> index 69509dbd01c7..b5af9c440ac5 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> @@ -59,6 +59,7 @@ i915_gem_object_create_shmem_from_data(struct drm_i915_private *i915,
>> const void *data, resource_size_t size);
>>
>> extern const struct drm_i915_gem_object_ops i915_gem_shmem_ops;
>> +
>> void __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
>> struct sg_table *pages,
>> bool needs_clflush);
>> @@ -278,12 +279,6 @@ i915_gem_object_never_mmap(const struct drm_i915_gem_object *obj)
>> return i915_gem_object_type_has(obj, I915_GEM_OBJECT_NO_MMAP);
>> }
>>
>> -static inline bool
>> -i915_gem_object_needs_async_cancel(const struct drm_i915_gem_object *obj)
>> -{
>> - return i915_gem_object_type_has(obj, I915_GEM_OBJECT_ASYNC_CANCEL);
>> -}
>> -
>> static inline bool
>> i915_gem_object_is_framebuffer(const struct drm_i915_gem_object *obj)
>> {
>> @@ -573,16 +568,6 @@ void __i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
>> void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
>> enum fb_op_origin origin);
>>
>> -static inline bool
>> -i915_gem_object_is_userptr(struct drm_i915_gem_object *obj)
>> -{
>> -#ifdef CONFIG_MMU_NOTIFIER
>> - return obj->userptr.mm;
>> -#else
>> - return false;
>> -#endif
>> -}
>> -
>> static inline void
>> i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
>> enum fb_op_origin origin)
>> @@ -603,4 +588,25 @@ int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset,
>>
>> bool i915_gem_object_is_shmem(const struct drm_i915_gem_object *obj);
>>
>> +#ifdef CONFIG_MMU_NOTIFIER
>> +static inline bool
>> +i915_gem_object_is_userptr(struct drm_i915_gem_object *obj)
>> +{
>> + return obj->userptr.notifier.mm;
>> +}
>> +
>> +int i915_gem_object_userptr_submit_init(struct drm_i915_gem_object *obj);
>> +int i915_gem_object_userptr_submit_done(struct drm_i915_gem_object *obj);
>> +void i915_gem_object_userptr_submit_fini(struct drm_i915_gem_object *obj);
>> +int i915_gem_object_userptr_validate(struct drm_i915_gem_object *obj);
>> +#else
>> +static inline bool i915_gem_object_is_userptr(struct drm_i915_gem_object *obj) { return false; }
>> +
>> +static inline int i915_gem_object_userptr_submit_init(struct drm_i915_gem_object *obj) { GEM_BUG_ON(1); return -ENODEV; }
>> +static inline int i915_gem_object_userptr_submit_done(struct drm_i915_gem_object *obj) { GEM_BUG_ON(1); return -ENODEV; }
>> +static inline void i915_gem_object_userptr_submit_fini(struct drm_i915_gem_object *obj) { GEM_BUG_ON(1); }
>> +static inline int i915_gem_object_userptr_validate(struct drm_i915_gem_object *obj) { GEM_BUG_ON(1); return -ENODEV; }
>> +
>> +#endif
>> +
>> #endif
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> index 414322619781..4c0a34231623 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>> @@ -7,6 +7,8 @@
>> #ifndef __I915_GEM_OBJECT_TYPES_H__
>> #define __I915_GEM_OBJECT_TYPES_H__
>>
>> +#include <linux/mmu_notifier.h>
>> +
>> #include <drm/drm_gem.h>
>> #include <uapi/drm/i915_drm.h>
>>
>> @@ -34,7 +36,6 @@ struct drm_i915_gem_object_ops {
>> #define I915_GEM_OBJECT_IS_SHRINKABLE BIT(2)
>> #define I915_GEM_OBJECT_IS_PROXY BIT(3)
>> #define I915_GEM_OBJECT_NO_MMAP BIT(4)
>> -#define I915_GEM_OBJECT_ASYNC_CANCEL BIT(5)
>>
>> /* Interface between the GEM object and its backing storage.
>> * get_pages() is called once prior to the use of the associated set
>> @@ -299,10 +300,11 @@ struct drm_i915_gem_object {
>> #ifdef CONFIG_MMU_NOTIFIER
>> struct i915_gem_userptr {
>> uintptr_t ptr;
>> + unsigned long notifier_seq;
>>
>> - struct i915_mm_struct *mm;
>> - struct i915_mmu_object *mmu_object;
>> - struct work_struct *work;
>> + struct mmu_interval_notifier notifier;
>> + struct page **pvec;
>> + int page_ref;
>> } userptr;
>> #endif
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> index bf61b88a2113..e7d7650072c5 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> @@ -226,7 +226,7 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
>> * get_pages backends we should be better able to handle the
>> * cancellation of the async task in a more uniform manner.
>> */
>> - if (!pages && !i915_gem_object_needs_async_cancel(obj))
>> + if (!pages)
>> pages = ERR_PTR(-EINVAL);
>>
>> if (!IS_ERR(pages))
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> index b466ab2def4d..1e42fbc68697 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> @@ -2,10 +2,39 @@
>> * SPDX-License-Identifier: MIT
>> *
>> * Copyright © 2012-2014 Intel Corporation
>> + *
>> + * Based on amdgpu_mn, which bears the following notice:
>> + *
>> + * Copyright 2014 Advanced Micro Devices, Inc.
>> + * All Rights Reserved.
>> + *
>> + * Permission is hereby granted, free of charge, to any person obtaining a
>> + * copy of this software and associated documentation files (the
>> + * "Software"), to deal in the Software without restriction, including
>> + * without limitation the rights to use, copy, modify, merge, publish,
>> + * distribute, sub license, and/or sell copies of the Software, and to
>> + * permit persons to whom the Software is furnished to do so, subject to
>> + * the following conditions:
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
>> + * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
>> + * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
>> + * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
>> + * USE OR OTHER DEALINGS IN THE SOFTWARE.
>> + *
>> + * The above copyright notice and this permission notice (including the
>> + * next paragraph) shall be included in all copies or substantial portions
>> + * of the Software.
>> + *
>> + */
>> +/*
>> + * Authors:
>> + * Christian König <christian.koenig@xxxxxxx>
>> */
>>
>> #include <linux/mmu_context.h>
>> -#include <linux/mmu_notifier.h>
>> #include <linux/mempolicy.h>
>> #include <linux/swap.h>
>> #include <linux/sched/mm.h>
>> @@ -15,373 +44,121 @@
>> #include "i915_gem_object.h"
>> #include "i915_scatterlist.h"
>>
>> -#if defined(CONFIG_MMU_NOTIFIER)
>> -
>> -struct i915_mm_struct {
>> - struct mm_struct *mm;
>> - struct drm_i915_private *i915;
>> - struct i915_mmu_notifier *mn;
>> - struct hlist_node node;
>> - struct kref kref;
>> - struct rcu_work work;
>> -};
>> -
>> -#include <linux/interval_tree.h>
>> -
>> -struct i915_mmu_notifier {
>> - spinlock_t lock;
>> - struct hlist_node node;
>> - struct mmu_notifier mn;
>> - struct rb_root_cached objects;
>> - struct i915_mm_struct *mm;
>> -};
>> -
>> -struct i915_mmu_object {
>> - struct i915_mmu_notifier *mn;
>> - struct drm_i915_gem_object *obj;
>> - struct interval_tree_node it;
>> -};
>> +#ifdef CONFIG_MMU_NOTIFIER
>>
>> -static void add_object(struct i915_mmu_object *mo)
>> +/**
>> + * i915_gem_userptr_invalidate - callback to notify about mm change
>> + *
>> + * @mni: the range (mm) is about to update
>> + * @range: details on the invalidation
>> + * @cur_seq: Value to pass to mmu_interval_set_seq()
>> + *
>> + * Block for operations on BOs to finish and mark pages as accessed and
>> + * potentially dirty.
>> + */
>> +static bool i915_gem_userptr_invalidate(struct mmu_interval_notifier *mni,
>> + const struct mmu_notifier_range *range,
>> + unsigned long cur_seq)
>> {
>> - GEM_BUG_ON(!RB_EMPTY_NODE(&mo->it.rb));
>> - interval_tree_insert(&mo->it, &mo->mn->objects);
>> -}
>> + struct drm_i915_gem_object *obj = container_of(mni, struct drm_i915_gem_object, userptr.notifier);
>> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
>> + long r;
>>
>> -static void del_object(struct i915_mmu_object *mo)
>> -{
>> - if (RB_EMPTY_NODE(&mo->it.rb))
>> - return;
>> + if (!mmu_notifier_range_blockable(range))
>> + return false;
>>
>> - interval_tree_remove(&mo->it, &mo->mn->objects);
>> - RB_CLEAR_NODE(&mo->it.rb);
>> -}
>> + spin_lock(&i915->mm.notifier_lock);
>>
>> -static void
>> -__i915_gem_userptr_set_active(struct drm_i915_gem_object *obj, bool value)
>> -{
>> - struct i915_mmu_object *mo = obj->userptr.mmu_object;
>> + mmu_interval_set_seq(mni, cur_seq);
>> +
>> + spin_unlock(&i915->mm.notifier_lock);
>>
>> /*
>> - * During mm_invalidate_range we need to cancel any userptr that
>> - * overlaps the range being invalidated. Doing so requires the
>> - * struct_mutex, and that risks recursion. In order to cause
>> - * recursion, the user must alias the userptr address space with
>> - * a GTT mmapping (possible with a MAP_FIXED) - then when we have
>> - * to invalidate that mmaping, mm_invalidate_range is called with
>> - * the userptr address *and* the struct_mutex held. To prevent that
>> - * we set a flag under the i915_mmu_notifier spinlock to indicate
>> - * whether this object is valid.
>> + * We don't wait when the process is exiting. This is valid
>> + * because the object will be cleaned up anyway.
>> + *
>> + * This is also temporarily required as a hack, because we
>> + * cannot currently force non-consistent batch buffers to preempt
>> + * and reschedule by waiting on it, hanging processes on exit.
>> */
>> - if (!mo)
>> - return;
>> -
>> - spin_lock(&mo->mn->lock);
>> - if (value)
>> - add_object(mo);
>> - else
>> - del_object(mo);
>> - spin_unlock(&mo->mn->lock);
>> -}
>> -
>> -static int
>> -userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
>> - const struct mmu_notifier_range *range)
>> -{
>> - struct i915_mmu_notifier *mn =
>> - container_of(_mn, struct i915_mmu_notifier, mn);
>> - struct interval_tree_node *it;
>> - unsigned long end;
>> - int ret = 0;
>> -
>> - if (RB_EMPTY_ROOT(&mn->objects.rb_root))
>> - return 0;
>> -
>> - /* interval ranges are inclusive, but invalidate range is exclusive */
>> - end = range->end - 1;
>> -
>> - spin_lock(&mn->lock);
>> - it = interval_tree_iter_first(&mn->objects, range->start, end);
>> - while (it) {
>> - struct drm_i915_gem_object *obj;
>> -
>> - if (!mmu_notifier_range_blockable(range)) {
>> - ret = -EAGAIN;
>> - break;
>> - }
>> -
>> - /*
>> - * The mmu_object is released late when destroying the
>> - * GEM object so it is entirely possible to gain a
>> - * reference on an object in the process of being freed
>> - * since our serialisation is via the spinlock and not
>> - * the struct_mutex - and consequently use it after it
>> - * is freed and then double free it. To prevent that
>> - * use-after-free we only acquire a reference on the
>> - * object if it is not in the process of being destroyed.
>> - */
>> - obj = container_of(it, struct i915_mmu_object, it)->obj;
>> - if (!kref_get_unless_zero(&obj->base.refcount)) {
>> - it = interval_tree_iter_next(it, range->start, end);
>> - continue;
>> - }
>> - spin_unlock(&mn->lock);
>> -
>> - ret = i915_gem_object_unbind(obj,
>> - I915_GEM_OBJECT_UNBIND_ACTIVE |
>> - I915_GEM_OBJECT_UNBIND_BARRIER);
>> - if (ret == 0)
>> - ret = __i915_gem_object_put_pages(obj);
>> - i915_gem_object_put(obj);
>> - if (ret)
>> - return ret;
>> + if (current->flags & PF_EXITING)
>> + return true;
>>
>> - spin_lock(&mn->lock);
>> -
>> - /*
>> - * As we do not (yet) protect the mmu from concurrent insertion
>> - * over this range, there is no guarantee that this search will
>> - * terminate given a pathologic workload.
>> - */
>> - it = interval_tree_iter_first(&mn->objects, range->start, end);
>> - }
>> - spin_unlock(&mn->lock);
>> -
>> - return ret;
>> + /* we will unbind on next submission, still have userptr pins */
>> + r = dma_resv_wait_timeout_rcu(obj->base.resv, true, false,
>> + MAX_SCHEDULE_TIMEOUT);
>> + if (r <= 0)
>> + drm_err(&i915->drm, "(%ld) failed to wait for idle\n", r);
>
> I think, since linux 5.9 where a fork is no longer setting up COW on pinned pages, and we do in fact still pin pages, I think this fence wait should be removed, together with the PF_EXIT special case, as it does not improve on anything but creates hangs that only hangcheck / watchdog can resolve. If we, in future work no longer pin the pages, which is the direction we're moving towards, let's re-add it when needed.
>
>>
>> + return true;
>> }
>>
>> -static const struct mmu_notifier_ops i915_gem_userptr_notifier = {
>> - .invalidate_range_start = userptr_mn_invalidate_range_start,
>> +static const struct mmu_interval_notifier_ops i915_gem_userptr_notifier_ops = {
>> + .invalidate = i915_gem_userptr_invalidate,
>> };
>>
>> -static struct i915_mmu_notifier *
>> -i915_mmu_notifier_create(struct i915_mm_struct *mm)
>> -{
>> - struct i915_mmu_notifier *mn;
>> -
>> - mn = kmalloc(sizeof(*mn), GFP_KERNEL);
>> - if (mn == NULL)
>> - return ERR_PTR(-ENOMEM);
>> -
>> - spin_lock_init(&mn->lock);
>> - mn->mn.ops = &i915_gem_userptr_notifier;
>> - mn->objects = RB_ROOT_CACHED;
>> - mn->mm = mm;
>> -
>> - return mn;
>> -}
>> -
>> -static void
>> -i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
>> -{
>> - struct i915_mmu_object *mo;
>> -
>> - mo = fetch_and_zero(&obj->userptr.mmu_object);
>> - if (!mo)
>> - return;
>> -
>> - spin_lock(&mo->mn->lock);
>> - del_object(mo);
>> - spin_unlock(&mo->mn->lock);
>> - kfree(mo);
>> -}
>> -
>> -static struct i915_mmu_notifier *
>> -i915_mmu_notifier_find(struct i915_mm_struct *mm)
>> -{
>> - struct i915_mmu_notifier *mn, *old;
>> - int err;
>> -
>> - mn = READ_ONCE(mm->mn);
>> - if (likely(mn))
>> - return mn;
>> -
>> - mn = i915_mmu_notifier_create(mm);
>> - if (IS_ERR(mn))
>> - return mn;
>> -
>> - err = mmu_notifier_register(&mn->mn, mm->mm);
>> - if (err) {
>> - kfree(mn);
>> - return ERR_PTR(err);
>> - }
>> -
>> - old = cmpxchg(&mm->mn, NULL, mn);
>> - if (old) {
>> - mmu_notifier_unregister(&mn->mn, mm->mm);
>> - kfree(mn);
>> - mn = old;
>> - }
>> -
>> - return mn;
>> -}
>> -
>> static int
>> i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj)
>> {
>> - struct i915_mmu_notifier *mn;
>> - struct i915_mmu_object *mo;
>> -
>> - if (GEM_WARN_ON(!obj->userptr.mm))
>> - return -EINVAL;
>> -
>> - mn = i915_mmu_notifier_find(obj->userptr.mm);
>> - if (IS_ERR(mn))
>> - return PTR_ERR(mn);
>> -
>> - mo = kzalloc(sizeof(*mo), GFP_KERNEL);
>> - if (!mo)
>> - return -ENOMEM;
>> -
>> - mo->mn = mn;
>> - mo->obj = obj;
>> - mo->it.start = obj->userptr.ptr;
>> - mo->it.last = obj->userptr.ptr + obj->base.size - 1;
>> - RB_CLEAR_NODE(&mo->it.rb);
>> -
>> - obj->userptr.mmu_object = mo;
>> - return 0;
>> -}
>> -
>> -static void
>> -i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
>> - struct mm_struct *mm)
>> -{
>> - if (mn == NULL)
>> - return;
>> -
>> - mmu_notifier_unregister(&mn->mn, mm);
>> - kfree(mn);
>> -}
>> -
>> -
>> -static struct i915_mm_struct *
>> -__i915_mm_struct_find(struct drm_i915_private *i915, struct mm_struct *real)
>> -{
>> - struct i915_mm_struct *it, *mm = NULL;
>> -
>> - rcu_read_lock();
>> - hash_for_each_possible_rcu(i915->mm_structs,
>> - it, node,
>> - (unsigned long)real)
>> - if (it->mm == real && kref_get_unless_zero(&it->kref)) {
>> - mm = it;
>> - break;
>> - }
>> - rcu_read_unlock();
>> -
>> - return mm;
>> + return mmu_interval_notifier_insert(&obj->userptr.notifier, current->mm,
>> + obj->userptr.ptr, obj->base.size,
>> + &i915_gem_userptr_notifier_ops);
>> }
>>
>> -static int
>> -i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
>> +static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
>> {
>> struct drm_i915_private *i915 = to_i915(obj->base.dev);
>> - struct i915_mm_struct *mm, *new;
>> - int ret = 0;
>> -
>> - /* During release of the GEM object we hold the struct_mutex. This
>> - * precludes us from calling mmput() at that time as that may be
>> - * the last reference and so call exit_mmap(). exit_mmap() will
>> - * attempt to reap the vma, and if we were holding a GTT mmap
>> - * would then call drm_gem_vm_close() and attempt to reacquire
>> - * the struct mutex. So in order to avoid that recursion, we have
>> - * to defer releasing the mm reference until after we drop the
>> - * struct_mutex, i.e. we need to schedule a worker to do the clean
>> - * up.
>> - */
>> - mm = __i915_mm_struct_find(i915, current->mm);
>> - if (mm)
>> - goto out;
>> + struct page **pvec = NULL;
>>
>> - new = kmalloc(sizeof(*mm), GFP_KERNEL);
>> - if (!new)
>> - return -ENOMEM;
>> -
>> - kref_init(&new->kref);
>> - new->i915 = to_i915(obj->base.dev);
>> - new->mm = current->mm;
>> - new->mn = NULL;
>> -
>> - spin_lock(&i915->mm_lock);
>> - mm = __i915_mm_struct_find(i915, current->mm);
>> - if (!mm) {
>> - hash_add_rcu(i915->mm_structs,
>> - &new->node,
>> - (unsigned long)new->mm);
>> - mmgrab(current->mm);
>> - mm = new;
>> + spin_lock(&i915->mm.notifier_lock);
>> + if (!--obj->userptr.page_ref) {
>> + pvec = obj->userptr.pvec;
>> + obj->userptr.pvec = NULL;
>> }
>> - spin_unlock(&i915->mm_lock);
>> - if (mm != new)
>> - kfree(new);
>> + GEM_BUG_ON(obj->userptr.page_ref < 0);
>> + spin_unlock(&i915->mm.notifier_lock);
>>
>> -out:
>> - obj->userptr.mm = mm;
>> - return ret;
>> -}
>> -
>> -static void
>> -__i915_mm_struct_free__worker(struct work_struct *work)
>> -{
>> - struct i915_mm_struct *mm = container_of(work, typeof(*mm), work.work);
>> -
>> - i915_mmu_notifier_free(mm->mn, mm->mm);
>> - mmdrop(mm->mm);
>> - kfree(mm);
>> -}
>> -
>> -static void
>> -__i915_mm_struct_free(struct kref *kref)
>> -{
>> - struct i915_mm_struct *mm = container_of(kref, typeof(*mm), kref);
>> -
>> - spin_lock(&mm->i915->mm_lock);
>> - hash_del_rcu(&mm->node);
>> - spin_unlock(&mm->i915->mm_lock);
>> -
>> - INIT_RCU_WORK(&mm->work, __i915_mm_struct_free__worker);
>> - queue_rcu_work(system_wq, &mm->work);
>> -}
>> -
>> -static void
>> -i915_gem_userptr_release__mm_struct(struct drm_i915_gem_object *obj)
>> -{
>> - if (obj->userptr.mm == NULL)
>> - return;
>> + if (pvec) {
>> + const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
>>
>> - kref_put(&obj->userptr.mm->kref, __i915_mm_struct_free);
>> - obj->userptr.mm = NULL;
>> + unpin_user_pages(pvec, num_pages);
>> + kfree(pvec);
>
> IIRC, CQ spotted that we should have a kvfree here right?
>
>> + }
>> }
>>
>> -struct get_pages_work {
>> - struct work_struct work;
>> - struct drm_i915_gem_object *obj;
>> - struct task_struct *task;
>> -};
>> -
>> -static struct sg_table *
>> -__i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
>> - struct page **pvec, unsigned long num_pages)
>> +static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
>> {
>> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
>> + const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
>> unsigned int max_segment = i915_sg_segment_size();
>> struct sg_table *st;
>> unsigned int sg_page_sizes;
>> struct scatterlist *sg;
>> + struct page **pvec;
>> int ret;
>>
>> st = kmalloc(sizeof(*st), GFP_KERNEL);
>> if (!st)
>> - return ERR_PTR(-ENOMEM);
>> + return -ENOMEM;
>> +
>> + spin_lock(&i915->mm.notifier_lock);
>> + if (GEM_WARN_ON(!obj->userptr.page_ref)) {
>> + spin_unlock(&i915->mm.notifier_lock);
>> + ret = -EFAULT;
>> + goto err_free;
>> + }
>> +
>> + obj->userptr.page_ref++;
>> + pvec = obj->userptr.pvec;
>> + spin_unlock(&i915->mm.notifier_lock);
>>
>> alloc_table:
>> sg = __sg_alloc_table_from_pages(st, pvec, num_pages, 0,
>> num_pages << PAGE_SHIFT, max_segment,
>> NULL, 0, GFP_KERNEL);
>> if (IS_ERR(sg)) {
>> - kfree(st);
>> - return ERR_CAST(sg);
>> + ret = PTR_ERR(sg);
>> + goto err;
>> }
>>
>> ret = i915_gem_gtt_prepare_pages(obj, st);
>> @@ -393,203 +170,20 @@ __i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
>> goto alloc_table;
>> }
>>
>> - kfree(st);
>> - return ERR_PTR(ret);
>> + goto err;
>> }
>>
>> sg_page_sizes = i915_sg_page_sizes(st->sgl);
>>
>> __i915_gem_object_set_pages(obj, st, sg_page_sizes);
>>
>> - return st;
>> -}
>> -
>> -static void
>> -__i915_gem_userptr_get_pages_worker(struct work_struct *_work)
>> -{
>> - struct get_pages_work *work = container_of(_work, typeof(*work), work);
>> - struct drm_i915_gem_object *obj = work->obj;
>> - const unsigned long npages = obj->base.size >> PAGE_SHIFT;
>> - unsigned long pinned;
>> - struct page **pvec;
>> - int ret;
>> -
>> - ret = -ENOMEM;
>> - pinned = 0;
>> -
>> - pvec = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
>> - if (pvec != NULL) {
>> - struct mm_struct *mm = obj->userptr.mm->mm;
>> - unsigned int flags = 0;
>> - int locked = 0;
>> -
>> - if (!i915_gem_object_is_readonly(obj))
>> - flags |= FOLL_WRITE;
>> -
>> - ret = -EFAULT;
>> - if (mmget_not_zero(mm)) {
>> - while (pinned < npages) {
>> - if (!locked) {
>> - mmap_read_lock(mm);
>> - locked = 1;
>> - }
>> - ret = pin_user_pages_remote
>> - (mm,
>> - obj->userptr.ptr + pinned * PAGE_SIZE,
>> - npages - pinned,
>> - flags,
>> - pvec + pinned, NULL, &locked);
>> - if (ret < 0)
>> - break;
>> -
>> - pinned += ret;
>> - }
>> - if (locked)
>> - mmap_read_unlock(mm);
>> - mmput(mm);
>> - }
>> - }
>> -
>> - mutex_lock_nested(&obj->mm.lock, I915_MM_GET_PAGES);
>> - if (obj->userptr.work == &work->work) {
>> - struct sg_table *pages = ERR_PTR(ret);
>> -
>> - if (pinned == npages) {
>> - pages = __i915_gem_userptr_alloc_pages(obj, pvec,
>> - npages);
>> - if (!IS_ERR(pages)) {
>> - pinned = 0;
>> - pages = NULL;
>> - }
>> - }
>> -
>> - obj->userptr.work = ERR_CAST(pages);
>> - if (IS_ERR(pages))
>> - __i915_gem_userptr_set_active(obj, false);
>> - }
>> - mutex_unlock(&obj->mm.lock);
>> -
>> - unpin_user_pages(pvec, pinned);
>> - kvfree(pvec);
>> -
>> - i915_gem_object_put(obj);
>> - put_task_struct(work->task);
>> - kfree(work);
>> -}
>> -
>> -static struct sg_table *
>> -__i915_gem_userptr_get_pages_schedule(struct drm_i915_gem_object *obj)
>> -{
>> - struct get_pages_work *work;
>> -
>> - /* Spawn a worker so that we can acquire the
>> - * user pages without holding our mutex. Access
>> - * to the user pages requires mmap_lock, and we have
>> - * a strict lock ordering of mmap_lock, struct_mutex -
>> - * we already hold struct_mutex here and so cannot
>> - * call gup without encountering a lock inversion.
>> - *
>> - * Userspace will keep on repeating the operation
>> - * (thanks to EAGAIN) until either we hit the fast
>> - * path or the worker completes. If the worker is
>> - * cancelled or superseded, the task is still run
>> - * but the results ignored. (This leads to
>> - * complications that we may have a stray object
>> - * refcount that we need to be wary of when
>> - * checking for existing objects during creation.)
>> - * If the worker encounters an error, it reports
>> - * that error back to this function through
>> - * obj->userptr.work = ERR_PTR.
>> - */
>> - work = kmalloc(sizeof(*work), GFP_KERNEL);
>> - if (work == NULL)
>> - return ERR_PTR(-ENOMEM);
>> -
>> - obj->userptr.work = &work->work;
>> -
>> - work->obj = i915_gem_object_get(obj);
>> -
>> - work->task = current;
>> - get_task_struct(work->task);
>> -
>> - INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker);
>> - queue_work(to_i915(obj->base.dev)->mm.userptr_wq, &work->work);
>> -
>> - return ERR_PTR(-EAGAIN);
>> -}
>> -
>> -static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
>> -{
>> - const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
>> - struct mm_struct *mm = obj->userptr.mm->mm;
>> - struct page **pvec;
>> - struct sg_table *pages;
>> - bool active;
>> - int pinned;
>> - unsigned int gup_flags = 0;
>> -
>> - /* If userspace should engineer that these pages are replaced in
>> - * the vma between us binding this page into the GTT and completion
>> - * of rendering... Their loss. If they change the mapping of their
>> - * pages they need to create a new bo to point to the new vma.
>> - *
>> - * However, that still leaves open the possibility of the vma
>> - * being copied upon fork. Which falls under the same userspace
>> - * synchronisation issue as a regular bo, except that this time
>> - * the process may not be expecting that a particular piece of
>> - * memory is tied to the GPU.
>> - *
>> - * Fortunately, we can hook into the mmu_notifier in order to
>> - * discard the page references prior to anything nasty happening
>> - * to the vma (discard or cloning) which should prevent the more
>> - * egregious cases from causing harm.
>> - */
>> -
>> - if (obj->userptr.work) {
>> - /* active flag should still be held for the pending work */
>> - if (IS_ERR(obj->userptr.work))
>> - return PTR_ERR(obj->userptr.work);
>> - else
>> - return -EAGAIN;
>> - }
>> -
>> - pvec = NULL;
>> - pinned = 0;
>> -
>> - if (mm == current->mm) {
>> - pvec = kvmalloc_array(num_pages, sizeof(struct page *),
>> - GFP_KERNEL |
>> - __GFP_NORETRY |
>> - __GFP_NOWARN);
>> - if (pvec) {
>> - /* defer to worker if malloc fails */
>> - if (!i915_gem_object_is_readonly(obj))
>> - gup_flags |= FOLL_WRITE;
>> - pinned = pin_user_pages_fast_only(obj->userptr.ptr,
>> - num_pages, gup_flags,
>> - pvec);
>> - }
>> - }
>> -
>> - active = false;
>> - if (pinned < 0) {
>> - pages = ERR_PTR(pinned);
>> - pinned = 0;
>> - } else if (pinned < num_pages) {
>> - pages = __i915_gem_userptr_get_pages_schedule(obj);
>> - active = pages == ERR_PTR(-EAGAIN);
>> - } else {
>> - pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
>> - active = !IS_ERR(pages);
>> - }
>> - if (active)
>> - __i915_gem_userptr_set_active(obj, true);
>> -
>> - if (IS_ERR(pages))
>> - unpin_user_pages(pvec, pinned);
>> - kvfree(pvec);
>> + return 0;
>>
>> - return PTR_ERR_OR_ZERO(pages);
>> +err:
>> + i915_gem_object_userptr_drop_ref(obj);
>> +err_free:
>> + kfree(st);
>> + return ret;
>> }
>>
>> static void
>> @@ -599,9 +193,6 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
>> struct sgt_iter sgt_iter;
>> struct page *page;
>>
>> - /* Cancel any inflight work and force them to restart their gup */
>> - obj->userptr.work = NULL;
>> - __i915_gem_userptr_set_active(obj, false);
>> if (!pages)
>> return;
>>
>> @@ -641,19 +232,161 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
>> }
>>
>> mark_page_accessed(page);
>> - unpin_user_page(page);
>> }
>> obj->mm.dirty = false;
>>
>> sg_free_table(pages);
>> kfree(pages);
>> +
>> + i915_gem_object_userptr_drop_ref(obj);
>> +}
>> +
>> +static int i915_gem_object_userptr_unbind(struct drm_i915_gem_object *obj, bool get_pages)
>> +{
>> + struct sg_table *pages;
>> + int err;
>> +
>> + err = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE);
>> + if (err)
>> + return err;
>> +
>> + if (GEM_WARN_ON(i915_gem_object_has_pinned_pages(obj)))
>> + return -EBUSY;
>> +
>> + mutex_lock_nested(&obj->mm.lock, I915_MM_GET_PAGES);
>> +
>> + pages = __i915_gem_object_unset_pages(obj);
>> + if (!IS_ERR_OR_NULL(pages))
>> + i915_gem_userptr_put_pages(obj, pages);
>> +
>> + if (get_pages)
>> + err = ____i915_gem_object_get_pages(obj);
>> + mutex_unlock(&obj->mm.lock);
>> +
>> + return err;
>> +}
>> +
>> +int i915_gem_object_userptr_submit_init(struct drm_i915_gem_object *obj)
>> +{
>> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
>> + const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
>> + struct page **pvec;
>> + unsigned int gup_flags = 0;
>> + unsigned long notifier_seq;
>> + int pinned, ret;
>> +
>> + if (obj->userptr.notifier.mm != current->mm)
>> + return -EFAULT;
>> +
>> + ret = i915_gem_object_lock_interruptible(obj, NULL);
>> + if (ret)
>> + return ret;
>> +
>> + /* Make sure userptr is unbound for next attempt, so we don't use stale pages. */
>> + ret = i915_gem_object_userptr_unbind(obj, false);
>> + i915_gem_object_unlock(obj);
>> + if (ret)
>> + return ret;
>> +
>> + notifier_seq = mmu_interval_read_begin(&obj->userptr.notifier);
>> +
>> + pvec = kvmalloc_array(num_pages, sizeof(struct page *), GFP_KERNEL);
>> + if (!pvec)
>> + return -ENOMEM;
>> +
>> + if (!i915_gem_object_is_readonly(obj))
>> + gup_flags |= FOLL_WRITE;
>> +
>> + pinned = ret = 0;
>> + while (pinned < num_pages) {
>> + ret = pin_user_pages_fast(obj->userptr.ptr + pinned * PAGE_SIZE,
>> + num_pages - pinned, gup_flags,
>> + &pvec[pinned]);
>> + if (ret < 0)
>> + goto out;
>> +
>> + pinned += ret;
>> + }
>> + ret = 0;
>> +
>> + spin_lock(&i915->mm.notifier_lock);
> I think we can improve a lot on the locking here by having the object lock protect the object state and only take the driver-wide notifier lock in execbuf / userptr_invalidate. If we in addition use an rwlock as a notifier lock taken in read mode in execbuf, any potential global lock contention can be practically eliminated. But that's perhaps for a future improvement.
>> +
>> + if (mmu_interval_read_retry(&obj->userptr.notifier,
>> + !obj->userptr.page_ref ? notifier_seq :
>> + obj->userptr.notifier_seq)) {
>> + ret = -EAGAIN;
>> + goto out_unlock;
>> + }
>> +
>> + if (!obj->userptr.page_ref++) {
>> + obj->userptr.pvec = pvec;
>> + obj->userptr.notifier_seq = notifier_seq;
>> +
>> + pvec = NULL;
>> + }
>
> In addition, if we can call get_pages() here to take the page_ref, we can eliminate one page_ref and the use of _userptr_submit_fini(). That would of course require the object lock, but we'd already hold that for the object state as above.
>
I guess it could be optimized by not doing this dance..
Perhaps this?
i915_gem_object_set_pages(pvec, seq)
{
i915_gem_object_lock_interruptible();
Directly run the set_pages() function body with pvec and seqno as argument. It will check for collisions, and return -EAGAIN if needed, 0 if notifier seqno was already set to same.
gem_object_unlock()
}
>> +
>> +out_unlock:
>> + spin_unlock(&i915->mm.notifier_lock);
>> +
>> +out:
>> + if (pvec) {
>> + unpin_user_pages(pvec, pinned);
>> + kvfree(pvec);
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +int i915_gem_object_userptr_submit_done(struct drm_i915_gem_object *obj)
>> +{
>> + if (mmu_interval_read_retry(&obj->userptr.notifier,
>> + obj->userptr.notifier_seq)) {
>> + /* We collided with the mmu notifier, need to retry */
>> +
>> + return -EAGAIN;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +void i915_gem_object_userptr_submit_fini(struct drm_i915_gem_object *obj)
>> +{
>> + i915_gem_object_userptr_drop_ref(obj);
>> +}
>> +
>> +int i915_gem_object_userptr_validate(struct drm_i915_gem_object *obj)
>> +{
>> + int err;
>> +
>> + err = i915_gem_object_userptr_submit_init(obj);
>> + if (err)
>> + return err;
>> +
>> + err = i915_gem_object_lock_interruptible(obj, NULL);
>> + if (!err) {
>> + /*
>> + * Since we only check validity, not use the pages,
>> + * it doesn't matter if we collide with the mmu notifier,
>> + * and -EAGAIN handling is not required.
>> + */
>> + err = i915_gem_object_pin_pages(obj);
>> + if (!err)
>> + i915_gem_object_unpin_pages(obj);
>> +
>> + i915_gem_object_unlock(obj);
>> + }
>> +
>> + i915_gem_object_userptr_submit_fini(obj);
>> + return err;
>> }
>>
>> static void
>> i915_gem_userptr_release(struct drm_i915_gem_object *obj)
>> {
>> - i915_gem_userptr_release__mmu_notifier(obj);
>> - i915_gem_userptr_release__mm_struct(obj);
>> + GEM_WARN_ON(obj->userptr.page_ref);
>> +
>> + mmu_interval_notifier_remove(&obj->userptr.notifier);
>> + obj->userptr.notifier.mm = NULL;
>> }
>>
>> static int
>> @@ -686,7 +419,6 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
>> .name = "i915_gem_object_userptr",
>> .flags = I915_GEM_OBJECT_IS_SHRINKABLE |
>> I915_GEM_OBJECT_NO_MMAP |
>> - I915_GEM_OBJECT_ASYNC_CANCEL |
>> I915_GEM_OBJECT_IS_PROXY,
>> .get_pages = i915_gem_userptr_get_pages,
>> .put_pages = i915_gem_userptr_put_pages,
>> @@ -793,6 +525,7 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
>> i915_gem_object_set_cache_coherency(obj, I915_CACHE_LLC);
>>
>> obj->userptr.ptr = args->user_ptr;
>> + obj->userptr.notifier_seq = ULONG_MAX;
>> if (args->flags & I915_USERPTR_READ_ONLY)
>> i915_gem_object_set_readonly(obj);
>>
>> @@ -800,9 +533,7 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
>> * at binding. This means that we need to hook into the mmu_notifier
>> * in order to detect if the mmu is destroyed.
>> */
>> - ret = i915_gem_userptr_init__mm_struct(obj);
>> - if (ret == 0)
>> - ret = i915_gem_userptr_init__mmu_notifier(obj);
>> + ret = i915_gem_userptr_init__mmu_notifier(obj);
>> if (ret == 0)
>> ret = drm_gem_handle_create(file, &obj->base, &handle);
>>
>> @@ -821,15 +552,7 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
>> int i915_gem_init_userptr(struct drm_i915_private *dev_priv)
>> {
>> #ifdef CONFIG_MMU_NOTIFIER
>> - spin_lock_init(&dev_priv->mm_lock);
>> - hash_init(dev_priv->mm_structs);
>> -
>> - dev_priv->mm.userptr_wq =
>> - alloc_workqueue("i915-userptr-acquire",
>> - WQ_HIGHPRI | WQ_UNBOUND,
>> - 0);
>> - if (!dev_priv->mm.userptr_wq)
>> - return -ENOMEM;
>> + spin_lock_init(&dev_priv->mm.notifier_lock);
>> #endif
>>
>> return 0;
>> @@ -837,7 +560,4 @@ int i915_gem_init_userptr(struct drm_i915_private *dev_priv)
>>
>> void i915_gem_cleanup_userptr(struct drm_i915_private *dev_priv)
>> {
>> -#ifdef CONFIG_MMU_NOTIFIER
>> - destroy_workqueue(dev_priv->mm.userptr_wq);
>> -#endif
>> }
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index fc41cf6442a9..72927d356c1a 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -558,11 +558,10 @@ struct i915_gem_mm {
>>
>> #ifdef CONFIG_MMU_NOTIFIER
>> /**
>> - * Workqueue to fault in userptr pages, flushed by the execbuf
>> - * when required but otherwise left to userspace to try again
>> - * on EAGAIN.
>> + * notifier_lock for mmu notifiers, memory may not be allocated
>> + * while holding this lock.
>> */
>> - struct workqueue_struct *userptr_wq;
>> + spinlock_t notifier_lock;
>> #endif
>>
>> /* shrinker accounting, also useful for userland debugging */
>> @@ -942,8 +941,6 @@ struct drm_i915_private {
>> struct i915_ggtt ggtt; /* VM representing the global address space */
>>
>> struct i915_gem_mm mm;
>> - DECLARE_HASHTABLE(mm_structs, 7);
>> - spinlock_t mm_lock;
>>
>> /* Kernel Modesetting */
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>> index 22be1e7bf2dd..6288cd5d898e 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -1053,10 +1053,8 @@ int i915_gem_init(struct drm_i915_private *dev_priv)
>> err_unlock:
>> i915_gem_drain_workqueue(dev_priv);
>>
>> - if (ret != -EIO) {
>> + if (ret != -EIO)
>> intel_uc_cleanup_firmwares(&dev_priv->gt.uc);
>> - i915_gem_cleanup_userptr(dev_priv);
>> - }
>>
>> if (ret == -EIO) {
>> /*
>> @@ -1113,7 +1111,6 @@ void i915_gem_driver_release(struct drm_i915_private *dev_priv)
>> intel_wa_list_free(&dev_priv->gt_wa_list);
>>
>> intel_uc_cleanup_firmwares(&dev_priv->gt.uc);
>> - i915_gem_cleanup_userptr(dev_priv);
>>
>> i915_gem_drain_freed_objects(dev_priv);
>>
>>
>> _______________________________________________
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>> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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