Just a trivial review of an the vm bind document that is still
an rfc document.
Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
---
Hi,
I'm not a big fan of this kind of patches, but while reading and
reviewing this document I spotted few potential grammatical fixes.
Andi
Documentation/gpu/rfc/i915_vm_bind.rst | 52 +++++++++++++-------------
1 file changed, 26 insertions(+), 26 deletions(-)
diff --git a/Documentation/gpu/rfc/i915_vm_bind.rst b/Documentation/gpu/rfc/i915_vm_bind.rst
index 9a1dcdf2799ef..78c17f345d82c 100644
--- a/Documentation/gpu/rfc/i915_vm_bind.rst
+++ b/Documentation/gpu/rfc/i915_vm_bind.rst
@@ -4,17 +4,17 @@ I915 VM_BIND feature design and use cases
VM_BIND feature
================
-DRM_I915_GEM_VM_BIND/UNBIND ioctls allows UMD to bind/unbind GEM buffer
+DRM_I915_GEM_VM_BIND/UNBIND ioctls allow UMD to bind/unbind GEM buffer
objects (BOs) or sections of a BOs at specified GPU virtual addresses on a
specified address space (VM). 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
+issued by the UMD, without the 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.
+VM_BIND feature is advertised to the 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.
@@ -33,8 +33,8 @@ VM_BIND features include:
TLB flush consideration
------------------------
The i915 driver flushes the TLB for each submission and when an object's
-pages are released. The VM_BIND/UNBIND operation will not do any additional
-TLB flush. Any VM_BIND mapping added will be in the working set for subsequent
+page is released. The VM_BIND/UNBIND operation will not do any additional TLB
+flush. Any VM_BIND mapping added will be in the working set for subsequent
submissions on that VM and will not be in the working set for currently running
batches (which would require additional TLB flushes, which is not supported).
@@ -57,13 +57,13 @@ works with execbuf3 ioctl for submission. All BOs mapped on that VM (through
VM_BIND call) at the time of execbuf3 call are deemed required for that
submission.
-The execbuf3 ioctl directly specifies the batch addresses instead of as
-object handles as in execbuf2 ioctl. The execbuf3 ioctl will also not
+The execbuf3 ioctl directly specifies the batch addresses instead of an
+object handle as in execbuf2 ioctl. The execbuf3 ioctl will also not
support many of the older features like in/out/submit fences, fence array,
default gem context and many more (See struct drm_i915_gem_execbuffer3).
In VM_BIND mode, VA allocation is completely managed by the user instead of
-the i915 driver. Hence all VA assignment, eviction are not applicable in
+the i915 driver. Hence all VA assignments and eviction are not applicable in
VM_BIND mode. Also, for determining object activeness, VM_BIND mode will not
be using the i915_vma active reference tracking. It will instead use dma-resv
object for that (See `VM_BIND dma_resv usage`_).
@@ -81,7 +81,7 @@ exported. Hence these BOs are referred to as Shared BOs.
During each execbuf submission, the request fence must be added to the
dma-resv fence list of all shared BOs mapped on the VM.
-VM_BIND feature introduces an optimization where user can create BO which
+VM_BIND feature introduces an optimization where the user can create a BO which
is private to a specified VM via I915_GEM_CREATE_EXT_VM_PRIVATE flag during
BO creation. Unlike Shared BOs, these VM private BOs can only be mapped on
the VM they are private to and can't be dma-buf exported.
@@ -95,7 +95,7 @@ VM_BIND locking hirarchy
The locking design here supports the older (execlist based) execbuf mode, the
newer VM_BIND mode, the VM_BIND mode with GPU page faults and possible future
system allocator support (See `Shared Virtual Memory (SVM) support`_).
-The older execbuf mode and the newer VM_BIND mode without page faults manages
+The older execbuf mode and the newer VM_BIND mode without page faults manage
residency of backing storage using dma_fence. The VM_BIND mode with page faults
and the system allocator support do not use any dma_fence at all.
@@ -105,10 +105,10 @@ VM_BIND locking order is as below.
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
+ In future, when GPU page faults will be supported, we will 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.
+ The older execbuf mode of binding does not need this lock.
2) Lock-B: 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
@@ -121,9 +121,9 @@ VM_BIND locking order is as below.
3) Lock-C: Spinlock/s to protect some of the VM's lists like the list of
invalidated vmas (due to eviction and userptr invalidation) etc.
-When GPU page faults are supported, the execbuf path do not take any of these
+When GPU page faults are supported, the execbuf path does not take any of these
locks. There we will simply smash the new batch buffer address into the ring and
-then tell the scheduler run that. The lock taking only happens from the page
+then tell the scheduler to run that. The locking only happens from the page
fault handler, where we take lock-A in read mode, whichever lock-B we need to
find the backing storage (dma_resv lock for gem objects, and hmm/core mm for
system allocator) and some additional locks (lock-D) for taking care of page
@@ -137,13 +137,13 @@ performance degradation. We will also need support for bulk LRU movement of
VM_BIND objects to avoid additional latencies in execbuf path.
The page table pages are similar to VM_BIND mapped objects (See
-`Evictable page table allocations`_) and are maintained per VM and needs to
+`Evictable page table allocations`_) and are maintained per VM and need to
be pinned in memory when VM is made active (ie., upon an execbuf call with
that VM). So, bulk LRU movement of page table pages is also needed.
VM_BIND dma_resv usage
-----------------------
-Fences needs to be added to all VM_BIND mapped objects. During each execbuf
+Fences need to be added to all VM_BIND mapped objects. During each execbuf
submission, they are added with DMA_RESV_USAGE_BOOKKEEP usage to prevent
over sync (See enum dma_resv_usage). One can override it with either
DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE usage during explicit object
@@ -188,7 +188,7 @@ User/Memory Fence
User/Memory fence is a <address, value> pair. To signal the user fence, the
specified value will be written at the specified virtual address and wakeup the
waiting process. User fence can be signaled either by the GPU or kernel async
-worker (like upon bind completion). User can wait on a user fence with a new
+worker (like upon bind completion). The user can wait on a user fence with a new
user fence wait ioctl.
Here is some prior work on this:
@@ -196,22 +196,22 @@ https://patchwork.freedesktop.org/patch/349417/
Low Latency Submission
~~~~~~~~~~~~~~~~~~~~~~~
-Allows compute UMD to directly submit GPU jobs instead of through execbuf
-ioctl. This is made possible by VM_BIND is not being synchronized against
+Allows compute UMD to directly submit GPU jobs instead of using execbuf
+ioctl. This is made possible by VM_BIND and it's not being synchronized against
execbuf. VM_BIND allows bind/unbind of mappings required for the directly
submitted jobs.
Debugger
---------
-With debug event interface user space process (debugger) is able to keep track
-of and act upon resources created by another process (debugged) and attached
-to GPU via vm_bind interface.
+With debug event interface the user space process (debugger) is able to keep
+track of and act upon resources created by another process (debugged) and
+attached to GPU via vm_bind interface.
GPU page faults
----------------
GPU page faults when supported (in future), will only be supported in the
VM_BIND mode. While both the older execbuf mode and the newer VM_BIND mode of
-binding will require using dma-fence to ensure residency, the GPU page faults
+binding will require using dma-fence to ensure residency, the GPU page fault
mode when supported, will not use any dma-fence as residency is purely managed
by installing and removing/invalidating page table entries.
@@ -229,15 +229,15 @@ Evictable page table allocations
---------------------------------
Make pagetable allocations evictable and manage them similar to VM_BIND
mapped objects. Page table pages are similar to persistent mappings of a
-VM (difference here are that the page table pages will not have an i915_vma
-structure and after swapping pages back in, parent page link needs to be
+VM (the difference here is that the page table pages will not have an i915_vma
+structure and after swapping pages back in, the parent page link needs to be
updated).
Shared Virtual Memory (SVM) support
------------------------------------
VM_BIND interface can be used to map system memory directly (without gem BO
abstraction) using the HMM interface. SVM is only supported with GPU page
-faults enabled.
+fault enabled.
VM_BIND UAPI
=============
--
2.36.1
