linux-kernel - Re: [PATCH] nouveau/svm: Fix to migrate all requested pages

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Date:   Thu, 28 Jul 2022 16:17:14 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Alistair Popple <apopple@...dia.com>, bskeggs@...hat.com,
        rcampbell@...dia.com
Cc:     kherbst@...hat.com, airlied@...ux.ie, daniel@...ll.ch,
        nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, jhubbard@...dia.com
Subject: Re: [PATCH] nouveau/svm: Fix to migrate all requested pages

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@...hat.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@...dia.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