Nouveau - Oct 2022 - [PATCH] nouveau: Fix migrate_to_ram() for faulting page

Commit 16ce101db85d ("mm/memory.c: fix race when faulting a device private
page") changed the migrate_to_ram() callback to take a reference on the
device page to ensure it can't be freed while handling the fault.
Unfortunately the corresponding update to Nouveau to accommodate this
change was inadvertently dropped from that patch causing GPU to CPU
migration to fail so add it here.

Signed-off-by: Alistair Popple <apopple at nvidia.com>
Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device private
page")
Cc: John Hubbard <jhubbard at nvidia.com>
Cc: Ralph Campbell <rcampbell at nvidia.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: Ben Skeggs <bskeggs at redhat.com>

---

Hi Andrew/Ben, apologies I must have accidentally dropped this small hunk
when rebasing prior to sending v2 of the original series. Without this
migration from GPU to CPU won't work in Nouveau so hopefully one of you can
take this for v6.1-rcX. Thanks.
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 5fe209107246..20fe53815b20 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -176,6 +176,7 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct
vm_fault *vmf)
 		.src		= &src,
 		.dst		= &dst,
 		.pgmap_owner	= drm->dev,
+		.fault_page	= vmf->page,
 		.flags		= MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
 	};
 
-- 
2.35.1

On Wed, 2022-10-19 at 23:29 +1100, Alistair Popple
wrote:
> Commit 16ce101db85d ("mm/memory.c: fix race when faulting a device
private
> page") changed the migrate_to_ram() callback to take a reference on
the
> device page to ensure it can't be freed while handling the fault.
> Unfortunately the corresponding update to Nouveau to accommodate this
> change was inadvertently dropped from that patch causing GPU to CPU
> migration to fail so add it here.
> 
> Signed-off-by: Alistair Popple <apopple at nvidia.com>
> Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device
private page")
> Cc: John Hubbard <jhubbard at nvidia.com>
> Cc: Ralph Campbell <rcampbell at nvidia.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> 
> ---
> 
> Hi Andrew/Ben, apologies I must have accidentally dropped this small hunk
> when rebasing prior to sending v2 of the original series. Without this
> migration from GPU to CPU won't work in Nouveau so hopefully one of you
can
> take this for v6.1-rcX. Thanks.
Hi!

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

I will push this to drm-misc-next in just a moment, thanks for the patch!
> ---
>  drivers/gpu/drm/nouveau/nouveau_dmem.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> index 5fe209107246..20fe53815b20 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> @@ -176,6 +176,7 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct
vm_fault *vmf)
>  		.src		= &src,
>  		.dst		= &dst,
>  		.pgmap_owner	= drm->dev,
> +		.fault_page	= vmf->page,
>  		.flags		= MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
>  	};
>  
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat