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Message-ID: <7f451c61-f45f-442f-b6fe-fac9ba0ea6d1@nvidia.com>
Date: Mon, 13 Oct 2025 09:54:09 +1100
From: Balbir Singh <balbirs@...dia.com>
To: Lance Yang <lance.yang@...ux.dev>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-mm@...ck.org, akpm@...ux-foundation.org,
David Hildenbrand <david@...hat.com>, Zi Yan <ziy@...dia.com>,
Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
Ying Huang <ying.huang@...ux.alibaba.com>,
Alistair Popple <apopple@...dia.com>, Oscar Salvador <osalvador@...e.de>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
Barry Song <baohua@...nel.org>, Lyude Paul <lyude@...hat.com>,
Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Ralph Campbell <rcampbell@...dia.com>,
Mika Penttilä <mpenttil@...hat.com>,
Matthew Brost <matthew.brost@...el.com>,
Francois Dugast <francois.dugast@...el.com>,
Madhavan Srinivasan <maddy@...ux.ibm.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Felix Kuehling <Felix.Kuehling@....com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>
Subject: Re: [v7 01/16] mm/zone_device: support large zone device private
folios
On 10/12/25 17:10, Lance Yang wrote:
> Hi Balbir,
>
> Just one nit below :)
>
> On Wed, Oct 1, 2025 at 3:43 PM Balbir Singh <balbirs@...dia.com> wrote:
>>
>> Add routines to support allocation of large order zone device folios
>> and helper functions for zone device folios, to check if a folio is
>> device private and helpers for setting zone device data.
>>
>> When large folios are used, the existing page_free() callback in
>> pgmap is called when the folio is freed, this is true for both
>> PAGE_SIZE and higher order pages.
>>
>> Zone device private large folios do not support deferred split and
>> scan like normal THP folios.
>>
>> Signed-off-by: Balbir Singh <balbirs@...dia.com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Zi Yan <ziy@...dia.com>
>> Cc: Joshua Hahn <joshua.hahnjy@...il.com>
>> Cc: Rakie Kim <rakie.kim@...com>
>> Cc: Byungchul Park <byungchul@...com>
>> Cc: Gregory Price <gourry@...rry.net>
>> Cc: Ying Huang <ying.huang@...ux.alibaba.com>
>> Cc: Alistair Popple <apopple@...dia.com>
>> Cc: Oscar Salvador <osalvador@...e.de>
>> Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
>> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>> Cc: Nico Pache <npache@...hat.com>
>> Cc: Ryan Roberts <ryan.roberts@....com>
>> Cc: Dev Jain <dev.jain@....com>
>> Cc: Barry Song <baohua@...nel.org>
>> Cc: Lyude Paul <lyude@...hat.com>
>> Cc: Danilo Krummrich <dakr@...nel.org>
>> Cc: David Airlie <airlied@...il.com>
>> Cc: Simona Vetter <simona@...ll.ch>
>> Cc: Ralph Campbell <rcampbell@...dia.com>
>> Cc: Mika Penttilä <mpenttil@...hat.com>
>> Cc: Matthew Brost <matthew.brost@...el.com>
>> Cc: Francois Dugast <francois.dugast@...el.com>
>> Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>
>> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
>> Cc: Felix Kuehling <Felix.Kuehling@....com>
>> Cc: Alex Deucher <alexander.deucher@....com>
>> Cc: "Christian König" <christian.koenig@....com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> ---
>> arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 2 +-
>> drivers/gpu/drm/drm_pagemap.c | 2 +-
>> drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
>> include/linux/memremap.h | 10 ++++++++-
>> lib/test_hmm.c | 2 +-
>> mm/memremap.c | 26 ++++++++++++++----------
>> mm/rmap.c | 6 +++++-
>> 8 files changed, 34 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> index 03f8c34fa0a2..91f763410673 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);
>> + zone_device_page_init(dpage, 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 79251f22b702..d0e2cae33035 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);
>> + zone_device_page_init(page, 0);
>> }
>>
>> static void
>> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
>> index 1da55322af12..31c53f724e25 100644
>> --- a/drivers/gpu/drm/drm_pagemap.c
>> +++ b/drivers/gpu/drm/drm_pagemap.c
>> @@ -196,7 +196,7 @@ 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);
>> + zone_device_page_init(page, 0);
>> }
>>
>> /**
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> index ca4932a150e3..53cc1926b9da 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> @@ -318,7 +318,7 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm)
>> return NULL;
>> }
>>
>> - zone_device_page_init(page);
>> + zone_device_page_init(page, 0);
>> return page;
>> }
>>
>> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
>> index e5951ba12a28..d2487a19cba2 100644
>> --- a/include/linux/memremap.h
>> +++ b/include/linux/memremap.h
>> @@ -206,7 +206,7 @@ static inline bool is_fsdax_page(const struct page *page)
>> }
>>
>> #ifdef CONFIG_ZONE_DEVICE
>> -void zone_device_page_init(struct page *page);
>> +void zone_device_page_init(struct page *page, 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);
>> @@ -215,6 +215,14 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn);
>> 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)
>> +{
>> + zone_device_page_init(&folio->page, order);
>> + if (order)
>> + folio_set_large_rmappable(folio);
>> +}
>> +
>> #else
>> static inline void *devm_memremap_pages(struct device *dev,
>> struct dev_pagemap *pgmap)
>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>> index 83e3d8208a54..24d82121cde8 100644
>> --- a/lib/test_hmm.c
>> +++ b/lib/test_hmm.c
>> @@ -627,7 +627,7 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
>> goto error;
>> }
>>
>> - zone_device_page_init(dpage);
>> + zone_device_page_init(dpage, 0);
>> dpage->zone_device_data = rpage;
>> return dpage;
>>
>> diff --git a/mm/memremap.c b/mm/memremap.c
>> index 46cb1b0b6f72..e45dfb568710 100644
>> --- a/mm/memremap.c
>> +++ b/mm/memremap.c
>> @@ -416,20 +416,19 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
>> void free_zone_device_folio(struct folio *folio)
>> {
>> struct dev_pagemap *pgmap = folio->pgmap;
>> + unsigned long nr = folio_nr_pages(folio);
>> + int i;
>>
>> if (WARN_ON_ONCE(!pgmap))
>> return;
>>
>> mem_cgroup_uncharge(folio);
>>
>> - /*
>> - * Note: we don't expect anonymous compound pages yet. Once supported
>> - * and we could PTE-map them similar to THP, we'd have to clear
>> - * PG_anon_exclusive on all tail pages.
>> - */
>> if (folio_test_anon(folio)) {
>> - VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
>> - __ClearPageAnonExclusive(folio_page(folio, 0));
>> + for (i = 0; i < nr; i++)
>> + __ClearPageAnonExclusive(folio_page(folio, i));
>> + } else {
>> + VM_WARN_ON_ONCE(folio_test_large(folio));
>> }
>>
>> /*
>> @@ -456,8 +455,8 @@ void free_zone_device_folio(struct folio *folio)
>> case MEMORY_DEVICE_COHERENT:
>> if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free))
>> break;
>> - pgmap->ops->page_free(folio_page(folio, 0));
>> - put_dev_pagemap(pgmap);
>> + pgmap->ops->page_free(&folio->page);
>> + percpu_ref_put_many(&folio->pgmap->ref, nr);
>
> Nit: &pgmap->ref here for consistency?
Can be done, thanks!
Balbir
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