Nouveau - Jul 2022 - [PATCH] nouveau/svm: Fix to migrate all requested pages

Users may request that pages from an OpenCL SVM allocation be migrated
to the GPU with clEnqueueSVMMigrateMem(). In Nouveau this will call into
nouveau_dmem_migrate_vma() to do the migration. If the total range to be
migrated exceeds SG_MAX_SINGLE_ALLOC the pages will be migrated in
chunks of size SG_MAX_SINGLE_ALLOC. However a typo in updating the
starting address means that only the first chunk will get migrated.

Fix the calculation so that the entire range will get migrated if
possible.

Signed-off-by: Alistair Popple <apopple at nvidia.com>
Fixes: e3d8b0890469 ("drm/nouveau/svm: map pages after migration")
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 7ba66ad68a8a..16356611b5b9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -680,7 +680,11 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 		goto out_free_dma;
 
 	for (i = 0; i < npages; i += max) {
-		args.end = start + (max << PAGE_SHIFT);
+		if (args.start + (max << PAGE_SHIFT) > end)
+			args.end = end;
+		else
+			args.end = args.start + (max << PAGE_SHIFT);
+
 		ret = migrate_vma_setup(&args);
 		if (ret)
 			goto out_free_pfns;
-- 
2.35.1

On 7/19/22 23:27, Alistair Popple wrote:
> Users may request that pages from an OpenCL SVM allocation be migrated
> to the GPU with clEnqueueSVMMigrateMem(). In Nouveau this will call into
> nouveau_dmem_migrate_vma() to do the migration. If the total range to be
> migrated exceeds SG_MAX_SINGLE_ALLOC the pages will be migrated in
> chunks of size SG_MAX_SINGLE_ALLOC. However a typo in updating the
> starting address means that only the first chunk will get migrated.
>
> Fix the calculation so that the entire range will get migrated if
> possible.
>
> Signed-off-by: Alistair Popple <apopple at nvidia.com>
> Fixes: e3d8b0890469 ("drm/nouveau/svm: map pages after
migration")
Thanks for fixing this!
Reviewed-by: Ralph Campbell <rcampbell at nvidia.com>

hi, in the future if it's taking a while for a review to come back feel free
to just send a poke on the thread for the patch you submitted, I do my best to
keep up with all of the patches coming in. But there's a lot of email that I
get so every now and then one slips through the cracks.

Anyway, this patch looks good to me:

Reviewed-by: Lyude Paul <lyude at redhat.com>

I will push it to the appropriate branch in a little bit

On Wed, 2022-07-20 at 16:27 +1000, Alistair Popple
wrote:
> Users may request that pages from an OpenCL SVM allocation be migrated
> to the GPU with clEnqueueSVMMigrateMem(). In Nouveau this will call into
> nouveau_dmem_migrate_vma() to do the migration. If the total range to be
> migrated exceeds SG_MAX_SINGLE_ALLOC the pages will be migrated in
> chunks of size SG_MAX_SINGLE_ALLOC. However a typo in updating the
> starting address means that only the first chunk will get migrated.
> 
> Fix the calculation so that the entire range will get migrated if
> possible.
> 
> Signed-off-by: Alistair Popple <apopple at nvidia.com>
> Fixes: e3d8b0890469 ("drm/nouveau/svm: map pages after
migration")
> ---
> ?drivers/gpu/drm/nouveau/nouveau_dmem.c | 6 +++++-
> ?1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> index 7ba66ad68a8a..16356611b5b9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> @@ -680,7 +680,11 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
> ????????????????goto out_free_dma;
> ?
> ????????for (i = 0; i < npages; i += max) {
> -???????????????args.end = start + (max << PAGE_SHIFT);
> +???????????????if (args.start + (max << PAGE_SHIFT) > end)
> +???????????????????????args.end = end;
> +???????????????else
> +???????????????????????args.end = args.start + (max << PAGE_SHIFT);
> +
> ????????????????ret = migrate_vma_setup(&args);
> ????????????????if (ret)
> ????????????????????????goto out_free_pfns;
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat