Re: [PATCH] drm/amdkfd: Fix partial migrate issue

[Felix Kuehling <felix.kuehling@xxxxxxx>]

On 2025-01-05 20:45, Deng, Emily wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
>
> > -----Original Message-----
> > From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
> > Sent: Saturday, January 4, 2025 7:10 AM
> > To: Deng, Emily <Emily.Deng@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH] drm/amdkfd: Fix partial migrate issue
> >
> >
> > On 2025-01-02 19:06, Emily Deng wrote:
> > > For partial migrate from ram to vram, the migrate->cpages is not equal
> > > to migrate->npages, should use migrate->npages to check all needed
> > > migrate pages which could be copied or not.
> > >
> > > And only need to set those pages could be migrated to migrate->dst[i],
> > > or the migrate_vma_pages will migrate the wrong pages based on the migrate-
> > > dst[i].
> > >
> > > Signed-off-by: Emily Deng <Emily.Deng@xxxxxxx>
> > Good catch. But I think it's still not quite right. See inline.
> >
> >
> > > ---
> > >    drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 8 ++++----
> > >    1 file changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > > b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > > index 4b275937d05e..5c96c2d425e3 100644
> > > --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > > @@ -278,7 +278,7 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct
> > svm_range *prange,
> > >                        struct migrate_vma *migrate, struct dma_fence **mfence,
> > >                        dma_addr_t *scratch, uint64_t ttm_res_offset)
> > >    {
> > > -    uint64_t npages = migrate->cpages;
> > > +    uint64_t npages = migrate->npages;
> > >       struct amdgpu_device *adev = node->adev;
> > >       struct device *dev = adev->dev;
> > >       struct amdgpu_res_cursor cursor;
> > > @@ -299,9 +299,6 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct
> > svm_range *prange,
> > >               struct page *spage;
> > >
> > >               dst[i] = cursor.start + (j << PAGE_SHIFT);
> > > -            migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
> > > -            svm_migrate_get_vram_page(prange, migrate->dst[i]);
> > > -            migrate->dst[i] = migrate_pfn(migrate->dst[i]);
> > >
> > >               spage = migrate_pfn_to_page(migrate->src[i]);
> > >               if (spage && !is_zone_device_page(spage)) {
> > We should also check (migrate->src[i] & MIGRATE_PFN_MIGRATE) to catch only the
> > pages that are ready to migrate (i.e. not already in device memory and not pinned by
> > someone else).
> >
> > Regards,
> >    Felix
> > The code " if (spage && !is_zone_device_page(spage)) {" is already checked whether the page could be migrated or not. Because after called migrate_vma_setup, for those pages couldn't be migrated it will be set to NULL.

The page may be non-NULL. If the MIGRATE_PFN_MIGRATE is not set, the 
page could not be collected for migration by migrate_vma_setup and it 
should not be migrated. See 
https://elixir.bootlin.com/linux/v6.12.6/source/mm/migrate_device.c#L470

Regards,
  Felix


> Emily Deng
> Best Wishes
>
>
> > > @@ -345,6 +342,9 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct
> > svm_range *prange,
> > >               } else {
> > >                       j++;
> > >               }
> > > +            migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
> > > +            svm_migrate_get_vram_page(prange, migrate->dst[i]);
> > > +            migrate->dst[i] = migrate_pfn(migrate->dst[i]);
> > >       }
> > >
> > >       r = svm_migrate_copy_memory_gart(adev, src + i - j, dst + i - j, j,