Re: [PATCH v5 1/5] mm/zone_device: Reinitialize large zone device private folios

Kuehling, Felix
2026-01-16T18:07:56Z

On 2026-01-16 11:43, Rodrigo Vivi wrote:
> On Wed, Jan 14, 2026 at 08:19:52PM +0100, Francois Dugast wrote:
>> From: Matthew Brost <matthew.brost@intel.com>
>>
>> Reinitialize metadata for large zone device private folios in
>> zone_device_page_init prior to creating a higher-order zone device
>> private folio. This step is necessary when the folio’s order changes
>> dynamically between zone_device_page_init calls to avoid building a
>> corrupt folio. As part of the metadata reinitialization, the dev_pagemap
>> must be passed in from the caller because the pgmap stored in the folio
>> page may have been overwritten with a compound head.
>>
>> Cc: Zi Yan <ziy@nvidia.com>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: adhavan Srinivasan <maddy@linux.ibm.com>
>> Cc: Nicholas Piggin <npiggin@gmail.com>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
>> Cc: Felix Kuehling <Felix.Kuehling@amd.com>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: "Christian König" <christian.koenig@amd.com>
>> Cc: David Airlie <airlied@gmail.com>
>> Cc: Simona Vetter <simona@ffwll.ch>
>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Cc: Maxime Ripard <mripard@kernel.org>
>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
>> Cc: Lyude Paul <lyude@redhat.com>
>> Cc: Danilo Krummrich <dakr@kernel.org>
>> Cc: David Hildenbrand <david@kernel.org>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>> Cc: Leon Romanovsky <leon@kernel.org>
>> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>> Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Mike Rapoport <rppt@kernel.org>
>> Cc: Suren Baghdasaryan <surenb@google.com>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Balbir Singh <balbirs@nvidia.com>
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Cc: kvm@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Cc: amd-gfx@lists.freedesktop.org
>> Cc: dri-devel@lists.freedesktop.org
>> Cc: nouveau@lists.freedesktop.org
>> Cc: linux-mm@kvack.org
>> Cc: linux-cxl@vger.kernel.org
>> Fixes: d245f9b4ab80 ("mm/zone_device: support large zone device private folios")
>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>> Signed-off-by: Francois Dugast <francois.dugast@intel.com>
>> ---
>> arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 2 +-
> AMD folks, ack to get this patch through drm-misc-next or even perhaps some mm
> related tree?

The kfd_migrate change looks straight-forward enough for me. We don't
use large device pages yet, so I guess the changes in
zone_device_page_init should be safe for us. Feel free to add  my

Acked-by: Felix Kuehling <felix.kuehling@amd.com>

I have no objections to merging this through drm-misc-next. @Alex, how
will this flow back into our amd-staging-drm-next branch? I guess we'll
get it on the next branch rebase. There should be no rush as I don't
think we're affected by the bug being fixed here.

Thanks,
Felix

>
>> drivers/gpu/drm/drm_pagemap.c | 2 +-
>> drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
> Nouveau folks, ack as well?
>
>> include/linux/memremap.h | 9 ++++++---
>> lib/test_hmm.c | 4 +++-
>> mm/memremap.c | 20 +++++++++++++++++++-
>> 7 files changed, 32 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> index e5000bef90f2..7cf9310de0ec 100644
>> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
>> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> @@ -723,7 +723,7 @@ static struct page *kvmppc_uvmem_get_page(unsigned long gpa, struct kvm *kvm)
>>
>> dpage = pfn_to_page(uvmem_pfn);
>> dpage->zone_device_data = pvt;
>> - zone_device_page_init(dpage, 0);
>> + zone_device_page_init(dpage, &kvmppc_uvmem_pgmap, 0);
>> return dpage;
>> out_clear:
>> spin_lock(&kvmppc_uvmem_bitmap_lock);
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> index af53e796ea1b..6ada7b4af7c6 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> @@ -217,7 +217,7 @@ svm_migrate_get_vram_page(struct svm_range *prange, unsigned long pfn)
>> page = pfn_to_page(pfn);
>> svm_range_bo_ref(prange->svm_bo);
>> page->zone_device_data = prange->svm_bo;
>> - zone_device_page_init(page, 0);
>> + zone_device_page_init(page, page_pgmap(page), 0);
>> }
>>
>> static void
>> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
>> index 03ee39a761a4..c497726b0147 100644
>> --- a/drivers/gpu/drm/drm_pagemap.c
>> +++ b/drivers/gpu/drm/drm_pagemap.c
>> @@ -201,7 +201,7 @@ static void drm_pagemap_get_devmem_page(struct page *page,
>> struct drm_pagemap_zdd *zdd)
>> {
>> page->zone_device_data = drm_pagemap_zdd_get(zdd);
>> - zone_device_page_init(page, 0);
>> + zone_device_page_init(page, zdd->dpagemap->pagemap, 0);
>> }
>>
>> /**
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> index 58071652679d..3d8031296eed 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> @@ -425,7 +425,7 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm, bool is_large)
>> order = ilog2(DMEM_CHUNK_NPAGES);
>> }
>>
>> - zone_device_folio_init(folio, order);
>> + zone_device_folio_init(folio, page_pgmap(folio_page(folio, 0)), order);
>> return page;
>> }
>>
>> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
>> index 713ec0435b48..e3c2ccf872a8 100644
>> --- a/include/linux/memremap.h
>> +++ b/include/linux/memremap.h
>> @@ -224,7 +224,8 @@ static inline bool is_fsdax_page(const struct page *page)
>> }
>>
>> #ifdef CONFIG_ZONE_DEVICE
>> -void zone_device_page_init(struct page *page, unsigned int order);
>> +void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap,
>> + unsigned int order);
>> void *memremap_pages(struct dev_pagemap *pgmap, int nid);
>> void memunmap_pages(struct dev_pagemap *pgmap);
>> void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
>> @@ -234,9 +235,11 @@ bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
>>
>> unsigned long memremap_compat_align(void);
>>
>> -static inline void zone_device_folio_init(struct folio *folio, unsigned int order)
>> +static inline void zone_device_folio_init(struct folio *folio,
>> + struct dev_pagemap *pgmap,
>> + unsigned int order)
>> {
>> - zone_device_page_init(&folio->page, order);
>> + zone_device_page_init(&folio->page, pgmap, order);
>> if (order)
>> folio_set_large_rmappable(folio);
>> }
>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>> index 8af169d3873a..455a6862ae50 100644
>> --- a/lib/test_hmm.c
>> +++ b/lib/test_hmm.c
>> @@ -662,7 +662,9 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror *dmirror,
>> goto error;
>> }
>>
>> - zone_device_folio_init(page_folio(dpage), order);
>> + zone_device_folio_init(page_folio(dpage),
>> + page_pgmap(folio_page(page_folio(dpage), 0)),
>> + order);
>> dpage->zone_device_data = rpage;
>> return dpage;
>>
>> diff --git a/mm/memremap.c b/mm/memremap.c
>> index 63c6ab4fdf08..6f46ab14662b 100644
>> --- a/mm/memremap.c
>> +++ b/mm/memremap.c
>> @@ -477,10 +477,28 @@ void free_zone_device_folio(struct folio *folio)
>> }
>> }
>>
>> -void zone_device_page_init(struct page *page, unsigned int order)
>> +void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap,
>> + unsigned int order)
>> {
>> + struct page *new_page = page;
>> + unsigned int i;
>> +
>> VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES);
>>
>> + for (i = 0; i < (1UL << order); ++i, ++new_page) {
>> + struct folio *new_folio = (struct folio *)new_page;
>> +
>> + new_page->flags.f &= ~0xffUL; /* Clear possible order, page head */
>> +#ifdef NR_PAGES_IN_LARGE_FOLIO
>> + ((struct folio *)(new_page - 1))->_nr_pages = 0;
>> +#endif
>> + new_folio->mapping = NULL;
>> + new_folio->pgmap = pgmap; /* Also clear compound head */
>> + new_folio->share = 0; /* fsdax only, unused for device private */
>> + VM_WARN_ON_FOLIO(folio_ref_count(new_folio), new_folio);
>> + VM_WARN_ON_FOLIO(!folio_is_zone_device(new_folio), new_folio);
>> + }
>> +
>> /*
>> * Drivers shouldn't be allocating pages after calling
>> * memunmap_pages().
>> --
>> 2.43.0
>>