[PATCH v4 2/2] drm/amdgpu: sync page table freeing with tlb flush
Christian König
christian.koenig at amd.com
Fri Mar 1 13:29:24 UTC 2024
Am 01.03.24 um 12:07 schrieb Shashank Sharma:
> The idea behind this patch is to delay the freeing of PT entry objects
> until the TLB flush is done.
>
> This patch:
> - Adds a tlb_flush_waitlist which will keep the objects that need to be
> freed after tlb_flush
> - Adds PT entries in this list in amdgpu_vm_pt_free_dfs, instead of freeing
> them immediately.
> - Exports function amdgpu_vm_pt_free to be called dircetly.
> - Adds a 'force' input bool to amdgpu_vm_pt_free_dfs to differentiate
> between immediate freeing of the BOs (like from
> amdgpu_vm_pt_free_root) vs delayed freeing.
>
> V2: rebase
> V4: (Christian)
> - add only locked PTEs entries in TLB flush waitlist.
> - do not create a separate function for list flush.
> - do not create a new lock for TLB flush.
> - there is no need to wait on tlb_flush_fence exclusively.
>
> Cc: Christian König <Christian.Koenig at amd.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Felix Kuehling <felix.kuehling at amd.com>
> Cc: Rajneesh Bhardwaj <rajneesh.bhardwaj at amd.com>
> Signed-off-by: Shashank Sharma <shashank.sharma at amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 10 ++++++++++
> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 4 ++++
> drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 21 ++++++++++++++-------
> 3 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 310aae6fb49b..94581a1fe34f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -990,11 +990,20 @@ int amdgpu_vm_update_range(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>
> /* Prepare a TLB flush fence to be attached to PTs */
> if (!unlocked && params.needs_flush && vm->is_compute_context) {
> + struct amdgpu_vm_bo_base *entry, *next;
> +
> amdgpu_vm_tlb_fence_create(adev, vm, fence);
>
> /* Makes sure no PD/PT is freed before the flush */
> dma_resv_add_fence(vm->root.bo->tbo.base.resv, *fence,
> DMA_RESV_USAGE_BOOKKEEP);
> +
> + if (list_empty(&vm->tlb_flush_waitlist))
> + goto error_unlock;
> +
> + /* Now actually free the waitlist */
> + list_for_each_entry_safe(entry, next, &vm->tlb_flush_waitlist, vm_status)
> + amdgpu_vm_pt_free(entry);
This needs to be outside of the "if". We also need to free the PDs/PTs
in non compute VMs.
> }
>
> error_unlock:
> @@ -2214,6 +2223,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
> INIT_LIST_HEAD(&vm->pt_freed);
> INIT_WORK(&vm->pt_free_work, amdgpu_vm_pt_free_work);
> INIT_KFIFO(vm->faults);
> + INIT_LIST_HEAD(&vm->tlb_flush_waitlist);
>
> r = amdgpu_seq64_alloc(adev, &vm->tlb_seq_va, &vm->tlb_seq_cpu_addr);
> if (r)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 298f604b8e5f..ba374c2c61bd 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -343,6 +343,9 @@ struct amdgpu_vm {
> uint64_t *tlb_seq_cpu_addr;
> uint64_t tlb_fence_context;
>
> + /* temporary storage of PT BOs until the TLB flush */
> + struct list_head tlb_flush_waitlist;
> +
> atomic64_t kfd_last_flushed_seq;
>
> /* How many times we had to re-generate the page tables */
> @@ -545,6 +548,7 @@ int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
> uint64_t start, uint64_t end,
> uint64_t dst, uint64_t flags);
> void amdgpu_vm_pt_free_work(struct work_struct *work);
> +void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry);
>
> #if defined(CONFIG_DEBUG_FS)
> void amdgpu_debugfs_vm_bo_info(struct amdgpu_vm *vm, struct seq_file *m);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> index 95dc0afdaffb..cb14e5686c0f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> @@ -636,7 +636,7 @@ static int amdgpu_vm_pt_alloc(struct amdgpu_device *adev,
> *
> * @entry: PDE to free
> */
> -static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
> +void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
> {
> struct amdgpu_bo *shadow;
>
> @@ -685,13 +685,15 @@ void amdgpu_vm_pt_free_work(struct work_struct *work)
> * @vm: amdgpu vm structure
> * @start: optional cursor where to start freeing PDs/PTs
> * @unlocked: vm resv unlock status
> + * @force: force free all PDs/PTs without waiting for TLB flush
> *
> * Free the page directory or page table level and all sub levels.
> */
> static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
> struct amdgpu_vm *vm,
> struct amdgpu_vm_pt_cursor *start,
> - bool unlocked)
> + bool unlocked,
> + bool force)
> {
> struct amdgpu_vm_pt_cursor cursor;
> struct amdgpu_vm_bo_base *entry;
> @@ -708,11 +710,15 @@ static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
> return;
> }
>
> - for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
> - amdgpu_vm_pt_free(entry);
> + for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry) {
> + if (!force)
> + list_move(&entry->vm_status, &vm->tlb_flush_waitlist);
> + else
> + amdgpu_vm_pt_free(entry);
> + }
>
> if (start)
> - amdgpu_vm_pt_free(start->entry);
> + list_move(&start->entry->vm_status, &vm->tlb_flush_waitlist);
> }
The complexity inside amdgpu_vm_pt_free_dfs() really starts to make no
sense any more.
First of all ditch the usage in amdgpu_vm_pt_free_root(). Instead just
inline the call to for_each_amdgpu_vm_pt_dfs_safe() to free up all of
the page tables immediately.
Then the other use case in amdgpu_vm_ptes_update():
/* Make sure previous mapping is freed */
if (cursor.entry->bo) {
params->table_freed = true;
amdgpu_vm_pt_free_dfs(adev, params->vm, &cursor, params->unlocked);
}
We should basically change params->table_freed into a list_head and put
all to be freed entries on there. Something like that:
spin_lock(&vm->status_lock);
for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
list_move(&entry->vm_status, ¶ms->table_freed);
spin_unlock(&vm->status_lock);
And then finally in amdgpu_vm_update_range() we should call
amdgpu_vm_pt_free_dfs() to really free up all PDs/PTs (probably rename
the function while at it).
Regards,
Christian.
>
> /**
> @@ -724,7 +730,7 @@ static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
> */
> void amdgpu_vm_pt_free_root(struct amdgpu_device *adev, struct amdgpu_vm *vm)
> {
> - amdgpu_vm_pt_free_dfs(adev, vm, NULL, false);
> + amdgpu_vm_pt_free_dfs(adev, vm, NULL, false, true);
> }
>
> /**
> @@ -1059,7 +1065,8 @@ int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
> params->needs_flush = true;
> amdgpu_vm_pt_free_dfs(adev, params->vm,
> &cursor,
> - params->unlocked);
> + params->unlocked,
> + false);
> }
> amdgpu_vm_pt_next(adev, &cursor);
> }
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