Re: [RFC PATCH v3 04/17] drm/i915: Implement bind and unbind of object

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On Tue, Aug 30, 2022 at 07:19:17PM +0100, Matthew Auld wrote:
On 27/08/2022 20:43, Andi Shyti wrote:
From: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>

Implement the bind and unbind of an object at the specified GPU virtual
addresses.

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan@xxxxxxxxx>
Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx>
Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/Makefile                 |   1 +
 drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h   |  21 ++
 .../drm/i915/gem/i915_gem_vm_bind_object.c    | 322 ++++++++++++++++++
 drivers/gpu/drm/i915/gt/intel_gtt.c           |  10 +
 drivers/gpu/drm/i915/gt/intel_gtt.h           |   9 +
 drivers/gpu/drm/i915/i915_driver.c            |   1 +
 drivers/gpu/drm/i915/i915_vma.c               |   3 +-
 drivers/gpu/drm/i915/i915_vma.h               |   2 -
 drivers/gpu/drm/i915/i915_vma_types.h         |  14 +
 include/uapi/drm/i915_drm.h                   | 163 +++++++++
 10 files changed, 543 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
 create mode 100644 drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 522ef9b4aff32..4e1627e96c6e0 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -165,6 +165,7 @@ gem-y += \
 	gem/i915_gem_ttm_move.o \
 	gem/i915_gem_ttm_pm.o \
 	gem/i915_gem_userptr.o \
+	gem/i915_gem_vm_bind_object.o \
 	gem/i915_gem_wait.o \
 	gem/i915_gemfs.o
 i915-y += \
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
new file mode 100644
index 0000000000000..ebc493b7dafc1
--- /dev/null
+++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2022 Intel Corporation
+ */
+
+#ifndef __I915_GEM_VM_BIND_H
+#define __I915_GEM_VM_BIND_H
+
+#include "i915_drv.h"
+
+struct i915_vma *
+i915_gem_vm_bind_lookup_vma(struct i915_address_space *vm, u64 va);
+void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj);
+
+int i915_gem_vm_bind_ioctl(struct drm_device *dev, void *data,
+			   struct drm_file *file);
+int i915_gem_vm_unbind_ioctl(struct drm_device *dev, void *data,
+			     struct drm_file *file);
+
+void i915_gem_vm_unbind_vma_all(struct i915_address_space *vm);
+#endif /* __I915_GEM_VM_BIND_H */
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
new file mode 100644
index 0000000000000..dadd1d4b1761b
--- /dev/null
+++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2022 Intel Corporation
+ */
+
+#include <linux/interval_tree_generic.h>
+
+#include "gem/i915_gem_vm_bind.h"
+#include "gem/i915_gem_context.h"
+#include "gt/gen8_engine_cs.h"
+
+#include "i915_drv.h"
+#include "i915_gem_gtt.h"
+
+#define START(node) ((node)->start)
+#define LAST(node) ((node)->last)
+
+INTERVAL_TREE_DEFINE(struct i915_vma, rb, u64, __subtree_last,
+		     START, LAST, static inline, i915_vm_bind_it)
+
+#undef START
+#undef LAST
+
+/**
+ * DOC: VM_BIND/UNBIND ioctls
+ *
+ * DRM_I915_GEM_VM_BIND/UNBIND ioctls allows UMD to bind/unbind GEM buffer
+ * objects (BOs) or sections of a BOs at specified GPU virtual addresses on a
+ * specified address space (VM). Multiple mappings can map to the same physical
+ * pages of an object (aliasing). These mappings (also referred to as persistent
+ * mappings) will be persistent across multiple GPU submissions (execbuf calls)
+ * issued by the UMD, without user having to provide a list of all required
+ * mappings during each submission (as required by older execbuf mode).
+ *
+ * The VM_BIND/UNBIND calls allow UMDs to request a timeline out fence for
+ * signaling the completion of bind/unbind operation.
+ *
+ * VM_BIND feature is advertised to user via I915_PARAM_VM_BIND_VERSION.
+ * User has to opt-in for VM_BIND mode of binding for an address space (VM)
+ * during VM creation time via I915_VM_CREATE_FLAGS_USE_VM_BIND extension.
+ *
+ * VM_BIND/UNBIND ioctl calls executed on different CPU threads concurrently
+ * are not ordered. Furthermore, parts of the VM_BIND/UNBIND operations can be
+ * done asynchronously, when valid out fence is specified.
+ *
+ * VM_BIND locking order is as below.
+ *
+ * 1) vm_bind_lock mutex will protect vm_bind lists. This lock is taken in
+ *    vm_bind/vm_unbind ioctl calls, in the execbuf path and while releasing the
+ *    mapping.
+ *
+ *    In future, when GPU page faults are supported, we can potentially use a
+ *    rwsem instead, so that multiple page fault handlers can take the read
+ *    side lock to lookup the mapping and hence can run in parallel.
+ *    The older execbuf mode of binding do not need this lock.
+ *
+ * 2) The object's dma-resv lock will protect i915_vma state and needs
+ *    to be held while binding/unbinding a vma in the async worker and while
+ *    updating dma-resv fence list of an object. Note that private BOs of a VM
+ *    will all share a dma-resv object.
+ *
+ * 3) Spinlock/s to protect some of the VM's lists like the list of
+ *    invalidated vmas (due to eviction and userptr invalidation) etc.
+ */
+
+/**
+ * i915_gem_vm_bind_lookup_vma() - lookup for the vma with a starting addr
+ * @vm: virtual address space in which vma needs to be looked for
+ * @va: starting addr of the vma
+ *
+ * retrieves the vma with a starting address from the vm's vma tree.
+ *
+ * Returns: returns vma on success, NULL on failure.
+ */
+struct i915_vma *
+i915_gem_vm_bind_lookup_vma(struct i915_address_space *vm, u64 va)
+{
+	lockdep_assert_held(&vm->vm_bind_lock);
+
+	return i915_vm_bind_it_iter_first(&vm->va, va, va);
+}
+
+/**
+ * i915_gem_vm_bind_remove() - Remove vma from the vm bind list
+ * @vma: vma that needs to be removed
+ * @release_obj: object to be release or not
+ *
+ * Removes the vma from the vm's lists custom interval tree
+ */
+void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj)
+{
+	lockdep_assert_held(&vma->vm->vm_bind_lock);
+
+	if (!list_empty(&vma->vm_bind_link)) {
+		list_del_init(&vma->vm_bind_link);
+		i915_vm_bind_it_remove(vma, &vma->vm->va);
+
+		/* Release object */
+		if (release_obj)
+			i915_gem_object_put(vma->obj);
+	}
+}
+
+static int i915_gem_vm_unbind_vma(struct i915_address_space *vm,
+				  struct i915_vma *vma,
+				  struct drm_i915_gem_vm_unbind *va)
+{
+	struct drm_i915_gem_object *obj;
+	int ret;
+
+	if (vma) {
+		obj = vma->obj;
+		i915_vma_destroy(vma);
+
+		goto exit;
+	}
+
+	if (!va)
+		return -EINVAL;
+
+	ret = mutex_lock_interruptible(&vm->vm_bind_lock);
+	if (ret)
+		return ret;
+
+	va->start = gen8_noncanonical_addr(va->start);
+	vma = i915_gem_vm_bind_lookup_vma(vm, va->start);
+
+	if (!vma)
+		ret = -ENOENT;
+	else if (vma->size != va->length)
+		ret = -EINVAL;
+
+	if (ret) {
+		mutex_unlock(&vm->vm_bind_lock);
+		return ret;
+	}
+
+	i915_gem_vm_bind_remove(vma, false);
+
+	mutex_unlock(&vm->vm_bind_lock);
+
+	/* Destroy vma and then release object */
+	obj = vma->obj;
+	ret = i915_gem_object_lock(obj, NULL);
+	if (ret)
+		return ret;
+
+	i915_vma_destroy(vma);
+	i915_gem_object_unlock(obj);
+
+exit:
+	i915_gem_object_put(obj);
+
+	return 0;
+}
+
+/**
+ * i915_gem_vm_unbind_vma_all() - Unbind all vmas from an address space
+ * @vm: Address spece from which vma binding needs to be removed
+ *
+ * Unbind all userspace requested object binding
+ */
+void i915_gem_vm_unbind_vma_all(struct i915_address_space *vm)
+{
+	struct i915_vma *vma, *t;
+
+	list_for_each_entry_safe(vma, t, &vm->vm_bound_list, vm_bind_link)
+		WARN_ON(i915_gem_vm_unbind_vma(vm, vma, NULL));
+}
+
+static struct i915_vma *vm_bind_get_vma(struct i915_address_space *vm,
+					struct drm_i915_gem_object *obj,
+					struct drm_i915_gem_vm_bind *va)
+{
+	struct i915_ggtt_view view;

Should that be renamed to i915_gtt_view? So all of this just works with ppgtt insertion, as-is? I'm impressed.

Yah, Tvrtko also gave the same comment on RFC v1.
Changing it to i915_gtt_view requires updating a lot of places.
Probably we should do that in a separate patch and push it first.
Yes, it does work for ppgtt. We just had to remove couple bug_on checks.


+	struct i915_vma *vma;
+
+	va->start = gen8_noncanonical_addr(va->start);
+	vma = i915_gem_vm_bind_lookup_vma(vm, va->start);
+	if (vma)
+		return ERR_PTR(-EEXIST);
+
+	view.type = I915_GGTT_VIEW_PARTIAL;
+	view.partial.offset = va->offset >> PAGE_SHIFT;
+	view.partial.size = va->length >> PAGE_SHIFT;
+	vma = i915_vma_instance(obj, vm, &view);
+	if (IS_ERR(vma))
+		return vma;
+
+	vma->start = va->start;
+	vma->last = va->start + va->length - 1;
+
+	return vma;
+}
+
+static int i915_gem_vm_bind_obj(struct i915_address_space *vm,
+				struct drm_i915_gem_vm_bind *va,
+				struct drm_file *file)
+{
+	struct drm_i915_gem_object *obj;
+	struct i915_vma *vma = NULL;
+	struct i915_gem_ww_ctx ww;
+	u64 pin_flags;
+	int ret = 0;
+
+	if (!vm->vm_bind_mode)
+		return -EOPNOTSUPP;
+
+	obj = i915_gem_object_lookup(file, va->handle);

AFAICT this doesn't have to be an object from gem_create/ext...

+	if (!obj)
+		return -ENOENT;
+
+	if (!va->length ||
+	    !IS_ALIGNED(va->offset | va->length,
+			i915_gem_object_max_page_size(obj->mm.placements,
+						      obj->mm.n_placements)) ||

...and so here max_page_size() can BUG_ON() if n_placements = 0. Also what should this return in that case?

Yah, in v1 version, i915_gem_object_max_page_size() doesn't have the BUG_ON()
and it does return 4K page size (as default size) if n_placements=0.
I think that would be the right way to go.

Niranjana




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