Hi Mauro,
I think there are still some unanswered questions from Tvrtko on
this patch, am I right?
Andi
On Wed, Jul 27, 2022 at 02:29:55PM +0200, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@xxxxxxxxx>
>
> Invalidate TLB in batches, in order to reduce performance regressions.
>
> Currently, every caller performs a full barrier around a TLB
> invalidation, ignoring all other invalidations that may have already
> removed their PTEs from the cache. As this is a synchronous operation
> and can be quite slow, we cause multiple threads to contend on the TLB
> invalidate mutex blocking userspace.
>
> We only need to invalidate the TLB once after replacing our PTE to
> ensure that there is no possible continued access to the physical
> address before releasing our pages. By tracking a seqno for each full
> TLB invalidate we can quickly determine if one has been performed since
> rewriting the PTE, and only if necessary trigger one for ourselves.
>
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
>
> [mchehab: rebased to not require moving the code to a separate file]
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Signed-off-by: Chris Wilson <chris.p.wilson@xxxxxxxxx>
> Cc: Fei Yang <fei.yang@xxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> ---
>
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v3 0/6] at: https://lore.kernel.org/all/cover.1658924372.git.mchehab@xxxxxxxxxx/
>
> .../gpu/drm/i915/gem/i915_gem_object_types.h | 3 +-
> drivers/gpu/drm/i915/gem/i915_gem_pages.c | 21 +++++---
> drivers/gpu/drm/i915/gt/intel_gt.c | 53 ++++++++++++++-----
> drivers/gpu/drm/i915/gt/intel_gt.h | 12 ++++-
> drivers/gpu/drm/i915/gt/intel_gt_types.h | 18 ++++++-
> drivers/gpu/drm/i915/gt/intel_ppgtt.c | 8 ++-
> drivers/gpu/drm/i915/i915_vma.c | 33 +++++++++---
> drivers/gpu/drm/i915/i915_vma.h | 1 +
> drivers/gpu/drm/i915/i915_vma_resource.c | 5 +-
> drivers/gpu/drm/i915/i915_vma_resource.h | 6 ++-
> 10 files changed, 125 insertions(+), 35 deletions(-)
>
> 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 5cf36a130061..9f6b14ec189a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -335,7 +335,6 @@ struct drm_i915_gem_object {
> #define I915_BO_READONLY BIT(7)
> #define I915_TILING_QUIRK_BIT 8 /* unknown swizzling; do not release! */
> #define I915_BO_PROTECTED BIT(9)
> -#define I915_BO_WAS_BOUND_BIT 10
> /**
> * @mem_flags - Mutable placement-related flags
> *
> @@ -616,6 +615,8 @@ struct drm_i915_gem_object {
> * pages were last acquired.
> */
> bool dirty:1;
> +
> + u32 tlb;
> } mm;
>
> struct {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 6835279943df..8357dbdcab5c 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -191,6 +191,18 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
> vunmap(ptr);
> }
>
> +static void flush_tlb_invalidate(struct drm_i915_gem_object *obj)
> +{
> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
> + struct intel_gt *gt = to_gt(i915);
> +
> + if (!obj->mm.tlb)
> + return;
> +
> + intel_gt_invalidate_tlb(gt, obj->mm.tlb);
> + obj->mm.tlb = 0;
> +}
> +
> struct sg_table *
> __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
> {
> @@ -216,14 +228,7 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
> __i915_gem_object_reset_page_iter(obj);
> obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;
>
> - if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
> - struct drm_i915_private *i915 = to_i915(obj->base.dev);
> - struct intel_gt *gt = to_gt(i915);
> - intel_wakeref_t wakeref;
> -
> - with_intel_gt_pm_if_awake(gt, wakeref)
> - intel_gt_invalidate_tlbs(gt);
> - }
> + flush_tlb_invalidate(obj);
>
> return pages;
> }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 5c55a90672f4..f435e06125aa 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -38,8 +38,6 @@ static void __intel_gt_init_early(struct intel_gt *gt)
> {
> spin_lock_init(>->irq_lock);
>
> - mutex_init(>->tlb_invalidate_lock);
> -
> INIT_LIST_HEAD(>->closed_vma);
> spin_lock_init(>->closed_lock);
>
> @@ -50,6 +48,8 @@ static void __intel_gt_init_early(struct intel_gt *gt)
> intel_gt_init_reset(gt);
> intel_gt_init_requests(gt);
> intel_gt_init_timelines(gt);
> + mutex_init(>->tlb.invalidate_lock);
> + seqcount_mutex_init(>->tlb.seqno, >->tlb.invalidate_lock);
> intel_gt_pm_init_early(gt);
>
> intel_uc_init_early(>->uc);
> @@ -770,6 +770,7 @@ void intel_gt_driver_late_release_all(struct drm_i915_private *i915)
> intel_gt_fini_requests(gt);
> intel_gt_fini_reset(gt);
> intel_gt_fini_timelines(gt);
> + mutex_destroy(>->tlb.invalidate_lock);
> intel_engines_free(gt);
> }
> }
> @@ -908,7 +909,7 @@ get_reg_and_bit(const struct intel_engine_cs *engine, const bool gen8,
> return rb;
> }
>
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> +static void mmio_invalidate_full(struct intel_gt *gt)
> {
> static const i915_reg_t gen8_regs[] = {
> [RENDER_CLASS] = GEN8_RTCR,
> @@ -931,12 +932,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> const i915_reg_t *regs;
> unsigned int num = 0;
>
> - if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> - return;
> -
> - if (intel_gt_is_wedged(gt))
> - return;
> -
> if (GRAPHICS_VER(i915) == 12) {
> regs = gen12_regs;
> num = ARRAY_SIZE(gen12_regs);
> @@ -951,9 +946,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> "Platform does not implement TLB invalidation!"))
> return;
>
> - GEM_TRACE("\n");
> -
> - mutex_lock(>->tlb_invalidate_lock);
> intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>
> spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
> @@ -973,6 +965,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> awake |= engine->mask;
> }
>
> + GT_TRACE(gt, "invalidated engines %08x\n", awake);
> +
> /* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
> if (awake &&
> (IS_TIGERLAKE(i915) ||
> @@ -1012,5 +1006,38 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> * transitions.
> */
> intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
> - mutex_unlock(>->tlb_invalidate_lock);
> +}
> +
> +static bool tlb_seqno_passed(const struct intel_gt *gt, u32 seqno)
> +{
> + u32 cur = intel_gt_tlb_seqno(gt);
> +
> + /* Only skip if a *full* TLB invalidate barrier has passed */
> + return (s32)(cur - ALIGN(seqno, 2)) > 0;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
> +{
> + intel_wakeref_t wakeref;
> +
> + if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> + return;
> +
> + if (intel_gt_is_wedged(gt))
> + return;
> +
> + if (tlb_seqno_passed(gt, seqno))
> + return;
> +
> + with_intel_gt_pm_if_awake(gt, wakeref) {
> + mutex_lock(>->tlb.invalidate_lock);
> + if (tlb_seqno_passed(gt, seqno))
> + goto unlock;
> +
> + mmio_invalidate_full(gt);
> +
> + write_seqcount_invalidate(>->tlb.seqno);
> +unlock:
> + mutex_unlock(>->tlb.invalidate_lock);
> + }
> }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
> index 82d6f248d876..40b06adf509a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.h
> @@ -101,6 +101,16 @@ void intel_gt_info_print(const struct intel_gt_info *info,
>
> void intel_gt_watchdog_work(struct work_struct *work);
>
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt);
> +static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
> +{
> + return seqprop_sequence(>->tlb.seqno);
> +}
> +
> +static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
> +{
> + return intel_gt_tlb_seqno(gt) | 1;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno);
>
> #endif /* __INTEL_GT_H__ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> index df708802889d..3804a583382b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> @@ -11,6 +11,7 @@
> #include <linux/llist.h>
> #include <linux/mutex.h>
> #include <linux/notifier.h>
> +#include <linux/seqlock.h>
> #include <linux/spinlock.h>
> #include <linux/types.h>
> #include <linux/workqueue.h>
> @@ -83,7 +84,22 @@ struct intel_gt {
> struct intel_uc uc;
> struct intel_gsc gsc;
>
> - struct mutex tlb_invalidate_lock;
> + struct {
> + /* Serialize global tlb invalidations */
> + struct mutex invalidate_lock;
> +
> + /*
> + * Batch TLB invalidations
> + *
> + * After unbinding the PTE, we need to ensure the TLB
> + * are invalidated prior to releasing the physical pages.
> + * But we only need one such invalidation for all unbinds,
> + * so we track how many TLB invalidations have been
> + * performed since unbind the PTE and only emit an extra
> + * invalidate if no full barrier has been passed.
> + */
> + seqcount_mutex_t seqno;
> + } tlb;
>
> struct i915_wa_list wa_list;
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> index d8b94d638559..2da6c82a8bd2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
> void ppgtt_unbind_vma(struct i915_address_space *vm,
> struct i915_vma_resource *vma_res)
> {
> - if (vma_res->allocated)
> - vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> + if (!vma_res->allocated)
> + return;
> +
> + vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> + if (vma_res->tlb)
> + vma_invalidate_tlb(vm, *vma_res->tlb);
> }
>
> static unsigned long pd_count(u64 size, int shift)
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index ef3b04c7e153..84a9ccbc5fc5 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -538,8 +538,6 @@ int i915_vma_bind(struct i915_vma *vma,
> bind_flags);
> }
>
> - set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
> -
> atomic_or(bind_flags, &vma->flags);
> return 0;
> }
> @@ -1310,6 +1308,19 @@ I915_SELFTEST_EXPORT int i915_vma_get_pages(struct i915_vma *vma)
> return err;
> }
>
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
> +{
> + /*
> + * Before we release the pages that were bound by this vma, we
> + * must invalidate all the TLBs that may still have a reference
> + * back to our physical address. It only needs to be done once,
> + * so after updating the PTE to point away from the pages, record
> + * the most recent TLB invalidation seqno, and if we have not yet
> + * flushed the TLBs upon release, perform a full invalidation.
> + */
> + WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));
> +}
> +
> static void __vma_put_pages(struct i915_vma *vma, unsigned int count)
> {
> /* We allocate under vma_get_pages, so beware the shrinker */
> @@ -1941,7 +1952,12 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
> vma->vm->skip_pte_rewrite;
> trace_i915_vma_unbind(vma);
>
> - unbind_fence = i915_vma_resource_unbind(vma_res);
> + if (async)
> + unbind_fence = i915_vma_resource_unbind(vma_res,
> + &vma->obj->mm.tlb);
> + else
> + unbind_fence = i915_vma_resource_unbind(vma_res, NULL);
> +
> vma->resource = NULL;
>
> atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
> @@ -1949,10 +1965,13 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
>
> i915_vma_detach(vma);
>
> - if (!async && unbind_fence) {
> - dma_fence_wait(unbind_fence, false);
> - dma_fence_put(unbind_fence);
> - unbind_fence = NULL;
> + if (!async) {
> + if (unbind_fence) {
> + dma_fence_wait(unbind_fence, false);
> + dma_fence_put(unbind_fence);
> + unbind_fence = NULL;
> + }
> + vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
> }
>
> /*
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index 88ca0bd9c900..5048eed536da 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -213,6 +213,7 @@ bool i915_vma_misplaced(const struct i915_vma *vma,
> u64 size, u64 alignment, u64 flags);
> void __i915_vma_set_map_and_fenceable(struct i915_vma *vma);
> void i915_vma_revoke_mmap(struct i915_vma *vma);
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb);
> struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async);
> int __i915_vma_unbind(struct i915_vma *vma);
> int __must_check i915_vma_unbind(struct i915_vma *vma);
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.c b/drivers/gpu/drm/i915/i915_vma_resource.c
> index 27c55027387a..5a67995ea5fe 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.c
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.c
> @@ -223,10 +223,13 @@ i915_vma_resource_fence_notify(struct i915_sw_fence *fence,
> * Return: A refcounted pointer to a dma-fence that signals when unbinding is
> * complete.
> */
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res)
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> + u32 *tlb)
> {
> struct i915_address_space *vm = vma_res->vm;
>
> + vma_res->tlb = tlb;
> +
> /* Reference for the sw fence */
> i915_vma_resource_get(vma_res);
>
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.h b/drivers/gpu/drm/i915/i915_vma_resource.h
> index 5d8427caa2ba..06923d1816e7 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.h
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.h
> @@ -67,6 +67,7 @@ struct i915_page_sizes {
> * taken when the unbind is scheduled.
> * @skip_pte_rewrite: During ggtt suspend and vm takedown pte rewriting
> * needs to be skipped for unbind.
> + * @tlb: pointer for obj->mm.tlb, if async unbind. Otherwise, NULL
> *
> * The lifetime of a struct i915_vma_resource is from a binding request to
> * the actual possible asynchronous unbind has completed.
> @@ -119,6 +120,8 @@ struct i915_vma_resource {
> bool immediate_unbind:1;
> bool needs_wakeref:1;
> bool skip_pte_rewrite:1;
> +
> + u32 *tlb;
> };
>
> bool i915_vma_resource_hold(struct i915_vma_resource *vma_res,
> @@ -131,7 +134,8 @@ struct i915_vma_resource *i915_vma_resource_alloc(void);
>
> void i915_vma_resource_free(struct i915_vma_resource *vma_res);
>
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res);
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> + u32 *tlb);
>
> void __i915_vma_resource_init(struct i915_vma_resource *vma_res);
>
> --
> 2.36.1
