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Message-ID: <CABzRoyYJXVdgTdoz9uYxeYHeejU1bbe6_rQnvbKns7fjvz_kqQ@mail.gmail.com>
Date: Sun, 12 Oct 2025 14:10:37 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Balbir Singh <balbirs@...dia.com>
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
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?
Cheers,
Lance
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