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b=NyRMpeAc4u6y1bOweC+oL1pis1n9yLFuTtLwnaUrYwqVmS04JztDPODWebMOjtgHG 8Fbr6g27cgQp5m17yZbh7JI8fGZ10S9y0Cr+pcX4HVLSzfam0/RHeiP22aiFXmTcSO m0JAkjjIdvcoeV0GjSXsbjx1PSem9FDJLdlR9l9XuQ7+JD77UCoo/+4blAoFrFHjtL 4lmP/E5Rc6HT7h8C6PmXHl7OCQQzJE8sLKpJ3BhxpLtIzac0pBDjbI8v8Sn+lsg4pM tBbGfrIkl+EK0Z5f0OcPdpEvn/ccg8GzXxJT1Z9Fkm2SnytuuVu3o7hx2RjZi50Rbj AaMG4PpMzZF8w== Message-ID: Date: Fri, 6 Mar 2026 17:03:57 +0100 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 From: "David Hildenbrand (Arm)" 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> Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: xjbisb199nbx7c7tjswxk1ds5xbbfic3 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: A02C24000D X-HE-Tag: 1772813049-628474 X-HE-Meta: U2FsdGVkX19yvLXmOMl8LCzG2ZZ7io0jvivVjyVbzw1hIRKcr/tcG5HlGqhE057RquM3yAtx04wVo7V7xgfoBhF1eOrQ/K2RBLujnns04ABwtyFqBj5g2VLp4Cuxpig/JM8KarWzNlyWkNkcUakpEFOBnD+IDfaCQzRdtgiC69Yam3+xFMp9qTama4WuX/West2jl9GAMQn/7bteO51b2yR/TQSd6yM3gQ8z8pLyanf7HYjAmKn7yh4Q4N9sCyg0j1yp3RhWLjrZiH3Euxv5/YlAkbRZ6ccru4Jy93XCzAmGH4M+3jth95c2aE+1XQRYNpDe6ADn6uTXSYAex34xsryXJRR29PotCiqawrJYTmYM8/zQ03Xl6KHWgbY3cTq/9NK8CQjX3KEMHBAKcCRWQpES/eXAF7hkzvcrfz5xf6NxyUqlnAV5x5eCJc8bH4x0eWOeNGrQuW2XS/Ka94oetM8P54gMKb5qt3ZZ8DD5wmouAEQ3ZeBwkvIYLno4+7qGLCQz5P5CpRLLfI7aq4T8slCkyB4F88fihMCOOnRDAPJlaZy9TyQccm6t94XhLHDJhEdxoipcDjUlEhDg/nFOqgqUnnfcjRxLFNzPRRX1yjjYa4qp3VG9kSRXK/OEDKeP9+Bb/A8pAJOAh5w6kfIZUUL3NgFtmjUadxYaQNDcMPtPnhBJSJBNaz3glWNKHWZPwrER2zVINAdYXnH7zr5q5O1hnOkKjvdvEbEzEy3lN+MW+dvx4o70Ecd3RDrq4vbo+FK4D+IjCLv4vrFVUyzWyigS5fr4k3H4W0EFdjdAP4HzXPi7Gq+ccRIjjSMTEa1ihKzLDvnC0U2ORLQ2t0y2RMrPrHkqYMik6I9XvXHDZ6C8LkyNymXH6E4zg1kXqG/Ekw9/BKK3DMQOERZk06aWL9EIwTKjWOfc91Ce6rmuQ7AewMtC26Y3UPsL0EAAeOLz3VzMqzH63D3uvo8BPKa bk1SfAsY F+BeAwVbqbaIL4hRX15QYp60RQD/S8ko0bvE4/RzCkBWF/JFtra7GN/aDdWaiGyUcO4mej834I7RjLSqC4K2vEFt/7ibU+Vwj5V9F38b/ZhQd3ILbu0xI2KBnljcvDpqWLAOrzdIDCXmt/Pzyzs+4V4ElARyByMkelCkvFOjUdi4gnkKT0P+8yGlg4SwDYq5EkaULZUcpR89swhdBK009tn4D5X8MGAXqiOoMJumYRQDM6Wy0d//0Bu/4uZAP8gx9f3WIiOpv5PLodUnKHeuz3inYMePm94UQcbrViaFGsZQJYvxA65i7voEXhEv6KXdVnGPc Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/6/26 17:02, David Hildenbrand (Arm) wrote: > 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? > Or maybe even better, if the pfn has no meaning, set it to 0 or -1, or anything that will make the other code just ignore it. -- Cheers, David