On 2026-01-16 11:43, Rodrigo Vivi wrote:

On Wed, Jan 14, 2026 at 08:19:52PM +0100, Francois Dugast wrote:

quoted

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 <redacted>
Cc: Liam R. Howlett <redacted>
Cc: Vlastimil Babka <redacted>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Balbir Singh <redacted>
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 <redacted>
---
  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

quoted

  drivers/gpu/drm/drm_pagemap.c            |  2 +-
  drivers/gpu/drm/nouveau/nouveau_dmem.c   |  2 +-

Nouveau folks, ack as well?

quoted

  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