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

Niranjana Vishwanathapura
2022-09-01T05:19:23Z

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@intel.com>
>>
>>Implement the bind and unbind of an object at the specified GPU virtual
>>addresses.
>>
>>Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
>>Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
>>Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
>>Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
>>---
>> 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