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Fri, 6 Mar 2026 16:02:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772812980; bh=/Ys4d0/mU9CmjC7P2UTEA2TWEWGsOTVSEX2kYD8lsO4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FC22dvTmruFfxpWA6NszR02HUo2o/qCQ0KdUmuj7ED8Er/3uYpMui5k5QgE4IY6WQ EGmUsIR4S72LF/kMcaxN9t669WYnACus4K3IOV+2wXDFFwMsbdnn9j6NhWdl8oeNoK 8oIq+df8Y7QHFsyOauk+pIwvlmjL4AhKZcMySpOJb7iiekjHby2I3ssMur6IDNk7wV Rol8lxycOQ6UIUSMtt8Qv17v36qJhsfb8lCXSxUgvksbk4XjOzIIQQYP6qdwT8wYAW ZnvRyA4BnwmIGdqnp0Zw9OPLq5fZgBsrlzuu/bRSrfi/5d/1Ne54tIyA3r715O/wvu kNrwR26Zee/zg== Message-ID: Date: Fri, 6 Mar 2026 17:02:49 +0100 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 11/13] mm/util: Add flag to track device private pages in page snapshots To: Jordan Niethe , linux-mm@kvack.org Cc: balbirs@nvidia.com, matthew.brost@intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, ziy@nvidia.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, lyude@redhat.com, dakr@kernel.org, airlied@gmail.com, simona@ffwll.ch, rcampbell@nvidia.com, mpenttil@redhat.com, jgg@nvidia.com, willy@infradead.org, linuxppc-dev@lists.ozlabs.org, intel-xe@lists.freedesktop.org, jgg@ziepe.ca, Felix.Kuehling@amd.com, jhubbard@nvidia.com, maddy@linux.ibm.com, mpe@ellerman.id.au, ying.huang@linux.alibaba.com References: <20260202113642.59295-1-jniethe@nvidia.com> <20260202113642.59295-12-jniethe@nvidia.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/2/26 12:36, Jordan Niethe wrote: > A future change will remove device private pages from the physical > address space. This will mean that device private pages no longer have > normal pfns and must be handled separately. > > Add a new flag PAGE_SNAPSHOT_DEVICE_PRIVATE to track when the pfn of a > page snapshot is a device private page. > > Signed-off-by: Jordan Niethe > Signed-off-by: Alistair Popple > --- > v1: > - No change > v2: > - No change > v3: > - No change > v4: > - Move logical continuation to previous line > --- > fs/proc/page.c | 6 ++++-- > include/linux/mm.h | 7 ++++--- > mm/util.c | 3 +++ > 3 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index f9b2c2c906cd..bc14f7ebc369 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -191,10 +191,12 @@ u64 stable_page_flags(const struct page *page) > folio_test_large_rmappable(folio)) { > /* Note: we indicate any THPs here, not just PMD-sized ones */ > u |= 1 << KPF_THP; > - } else if (is_huge_zero_pfn(ps.pfn)) { > + } else if (!(ps.flags & PAGE_SNAPSHOT_DEVICE_PRIVATE) && > + is_huge_zero_pfn(ps.pfn)) { > u |= 1 << KPF_ZERO_PAGE; > u |= 1 << KPF_THP; > - } else if (is_zero_pfn(ps.pfn)) { > + } else if (!(ps.flags & PAGE_SNAPSHOT_DEVICE_PRIVATE) && > + is_zero_pfn(ps.pfn)) { > u |= 1 << KPF_ZERO_PAGE; > } > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f0d5be9dc736..a52979536a5e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4627,9 +4627,10 @@ static inline bool page_pool_page_is_pp(const struct page *page) > } > #endif > > -#define PAGE_SNAPSHOT_FAITHFUL (1 << 0) > -#define PAGE_SNAPSHOT_PG_BUDDY (1 << 1) > -#define PAGE_SNAPSHOT_PG_IDLE (1 << 2) > +#define PAGE_SNAPSHOT_FAITHFUL (1 << 0) > +#define PAGE_SNAPSHOT_PG_BUDDY (1 << 1) > +#define PAGE_SNAPSHOT_PG_IDLE (1 << 2) > +#define PAGE_SNAPSHOT_DEVICE_PRIVATE (1 << 3) > > struct page_snapshot { > struct folio folio_snapshot; > diff --git a/mm/util.c b/mm/util.c > index 97cae40c0209..65e3f1a97d76 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -1218,6 +1218,9 @@ static void set_ps_flags(struct page_snapshot *ps, const struct folio *folio, > > if (folio_test_idle(folio)) > ps->flags |= PAGE_SNAPSHOT_PG_IDLE; > + > + if (is_device_private_page(page)) > + ps->flags |= PAGE_SNAPSHOT_DEVICE_PRIVATE; stable_page_flags() has access to the page and can simply test that instead? -- Cheers, David