From: "Yadav, Arvind" <arvind.yadav@intel.com>
To: Matthew Brost <matthew.brost@intel.com>
Cc: <intel-xe@lists.freedesktop.org>,
<himal.prasad.ghimiray@intel.com>,
<thomas.hellstrom@linux.intel.com>
Subject: Re: [RFC v2 3/7] drm/xe/svm: Clear CPU_AUTORESET_ACTIVE on first GPU fault
Date: Thu, 4 Jun 2026 11:08:40 +0530 [thread overview]
Message-ID: <a5c8de9c-41e8-4f63-bad5-5dd93ab56d97@intel.com> (raw)
In-Reply-To: <afLaCi80ZDcEFKB+@gsse-cloud1.jf.intel.com>
On 30-04-2026 09:56, Matthew Brost wrote:
> On Mon, Apr 06, 2026 at 02:28:26PM +0530, Arvind Yadav wrote:
>> CPU address mirror VMAs start with cpu_autoreset_active set, indicating
>> they are still CPU-only.
>>
>> Clear cpu_autoreset_active after the first successful GPU fault so
>> subsequent munmap follows the SVM path instead of the autoreset path.
>>
>> Do this in xe_svm_handle_pagefault() on the success path only.
>> Prefetch faults that install no PTEs must not transition this state.
>>
>> v2:
>> - Move xe_vma_gpu_touch() to the success path in
>> xe_svm_handle_pagefault() so prefetch faults that find no range do
>> not transition the state. (Matt)
>> - Add xe_vma_gpu_touch() helper in xe_vm.h and use
>> vma->cpu_autoreset_active instead of vma->gpuva.flags. (Matt)
>>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
>> ---
>> drivers/gpu/drm/xe/xe_svm.c | 11 +++++++++++
>> drivers/gpu/drm/xe/xe_vm.h | 13 +++++++++++++
>> 2 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
>> index 5933b2b6392b..fd57c9d41db8 100644
>> --- a/drivers/gpu/drm/xe/xe_svm.c
>> +++ b/drivers/gpu/drm/xe/xe_svm.c
>> @@ -1388,6 +1388,9 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
>> bool atomic)
>> {
>> int need_vram, ret;
>> +
>> + lockdep_assert_held_write(&vm->lock);
>> +
> This looks unrelated... and will change here [1] to read mode.
>
> [1] https://patchwork.freedesktop.org/patch/707294/?series=162167&rev=4
>
> So I'd say drop this part.
Agreed, I dropped this in next version.
>
>> retry:
>> need_vram = xe_vma_need_vram_for_atomic(vm->xe, vma, atomic);
>> if (need_vram < 0)
>> @@ -1406,6 +1409,14 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
>>
>> goto retry;
>> }
>> +
>> + /*
>> + * Mark the VMA as GPU-touched only after a successful fault-in.
>> + * Prefetch faults that find no range must not transition this state.
>> + */
>> + if (!ret && xe_vma_has_cpu_autoreset_active(vma))
>> + xe_vma_gpu_touch(vma);
>> +
>> return ret;
>> }
>>
>> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
>> index bdf42083da86..8d45f896f90b 100644
>> --- a/drivers/gpu/drm/xe/xe_vm.h
>> +++ b/drivers/gpu/drm/xe/xe_vm.h
>> @@ -441,4 +441,17 @@ static inline struct drm_exec *xe_vm_validation_exec(struct xe_vm *vm)
>> ((READ_ONCE(tile_present) & ~READ_ONCE(tile_invalidated)) & BIT((tile)->id))
>>
>> void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *from);
>> +
>> +/**
>> + * xe_vma_gpu_touch() - Mark a VMA as no longer CPU-only
>> + * @vma: VMA to update
>> + *
>> + * Clear cpu_autoreset_active after the first successful GPU fault-in.
>> + * Caller must hold vm->lock in write mode.
>> + */
>> +static inline void xe_vma_gpu_touch(struct xe_vma *vma)
>> +{
>> + lockdep_assert_held_write(&xe_vma_vm(vma)->lock);
>> + vma->cpu_autoreset_active = false;
> Write mode VM lock seems fine for now, but will likely have to change
> this to vma->fault_lock with [1]...
Noted. I am keeping this series aligned with the current locking for
now. Once the parallel fault handling changes land, I will update this
path to follow the new `vma->fault_lock`.
>
> Also IMO the caller adjusting this is too late. Adjusting auto-reset
> likely should be basically be the first thing handler does, moved to the
> xe_pagefault layer... I noticed in [1] the VMA more than likely needs to
> be refcounted but that's a different issue.
Agreed, I will move the autoreset transition to
`xe_pagefault_service()` after successful fault handling.
> Lastly - when we call xe_vma_gpu_touch and go from cpu_autoreset_active
> 1 -> 0 shouldn't we remove the auto-reset notifier [2] [3]? Keeping
> notifier around is a non-zero cost as these are entiries in interval
> tree the core MM walks for every notifier trigger, so I think deleting
> the notifier part makes sense if this is possible - still wrapping my
> head around [2] [3], so take this as a suggestion.
I disable only exact-match notifiers after GPU touch. Broader notifiers
stay active for CPU-only split siblings. Full removal can be revisited
after the fault-lock changes settle.
Thanks,
Arvind
>
> Matt
>
> [2] https://patchwork.freedesktop.org/patch/716552/?series=161815&rev=2
> [3] https://patchwork.freedesktop.org/patch/716553/?series=161815&rev=2
>
>> +}
>> #endif
>> --
>> 2.43.0
>>
next prev parent reply other threads:[~2026-06-04 5:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-06 8:58 [RFC v2 0/7] drm/xe/svm: Add MMU notifier-based madvise autoreset on munmap Arvind Yadav
2026-04-06 8:58 ` [RFC v2 1/7] drm/xe/vm: Track CPU_AUTORESET state in xe_vma Arvind Yadav
2026-04-30 4:07 ` Matthew Brost
2026-06-04 5:31 ` Yadav, Arvind
2026-04-06 8:58 ` [RFC v2 2/7] drm/xe/vm: Preserve cpu_autoreset_active across GPUVA operations Arvind Yadav
2026-04-30 4:29 ` Matthew Brost
2026-06-04 5:40 ` Yadav, Arvind
2026-04-06 8:58 ` [RFC v2 3/7] drm/xe/svm: Clear CPU_AUTORESET_ACTIVE on first GPU fault Arvind Yadav
2026-04-30 4:26 ` Matthew Brost
2026-06-04 5:38 ` Yadav, Arvind [this message]
2026-04-06 8:58 ` [RFC v2 4/7] drm/xe/vm: Add madvise autoreset interval notifier worker infrastructure Arvind Yadav
2026-04-06 8:58 ` [RFC v2 5/7] drm/xe/vm: Deactivate madvise notifier on GPU touch Arvind Yadav
2026-04-06 8:58 ` [RFC v2 6/7] drm/xe/vm: Wire MADVISE_AUTORESET notifiers into VM lifecycle Arvind Yadav
2026-04-06 8:58 ` [RFC v2 7/7] drm/xe/svm: Correct memory attribute reset for partial unmap Arvind Yadav
2026-04-30 5:02 ` Matthew Brost
2026-04-30 5:08 ` Matthew Brost
2026-06-04 6:05 ` Yadav, Arvind
2026-04-06 9:04 ` ✗ CI.checkpatch: warning for drm/xe/svm: Add MMU notifier-based madvise autoreset on munmap (rev2) Patchwork
2026-04-06 9:06 ` ✓ CI.KUnit: success " Patchwork
2026-04-06 9:54 ` ✓ Xe.CI.BAT: " Patchwork
2026-04-06 12:36 ` ✓ Xe.CI.FULL: " Patchwork
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