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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-454916df968sm36702334f8f.25.2026.05.12.14.06.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 14:06:58 -0700 (PDT) Date: Tue, 12 May 2026 17:06:53 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: [PATCH v7 20/31] mm: page_reporting: add per-page zeroed bitmap for host feedback Message-ID: <929bcbf8d4bdd51c038ec302e2db26d82d942ba9.1778616612.git.mst@redhat.com> References: MIME-Version: 1.0 In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: wP2NKz5ged5dhgGEBa_xH0PX08fAy-APDtGiFKnRtHA_1778620020 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Queue-Id: C5BFC4000B X-Rspamd-Server: rspam04 X-Stat-Signature: 7o6o6qg3ubsc8s3us65royb36g34g1j8 X-HE-Tag: 1778620022-421666 X-HE-Meta: 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 ni+q2+JM 11o9IKuyC4rWxC4aT9afQeWsCiZasIgI+gkslLi8ff2TGx+TRMGQT4ctm0jMPYcgc3NOmDz2/d4R8vAZ7clU8vcp02C/Bh9c+OH2Cgmuf5w3f15GNmcbgUSSDCQAPSwFOT98KDDRHx2dpxImZZKCgKBXc2imYQ5c/RrF/fRFEn6zcQqDWm8BZokx8xxiOkq0RNrsfDIsYVALUSD2vjil41CmQcMd6sa2ylt57Y2SKe+gE3aFSRuwuz7OQFmaN3tjbgrfHkkf1EJ8BVISFnwzza8ukipfnbFWxsFYF4OGgyesL/tT1+zMnelWVpnKXisuiqeq1QhnoTvpzjy+/PKHvDQZ1PmdQt4cdq7VpSCcICOm6rt5BRCOzgnNYdJlJKy1t+bJ3m9DGH7lxE8Xi5aS/jkfPtLXWF9IC11ejyzeGSbx0swjGdl/JHcTymv0gUzvFWRHb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The host may skip zeroing some reported pages (e.g., due to alignment constraints or bounce buffer fallback in QEMU). Currently, when host_zeroes_pages is set, all reported pages are unconditionally marked PG_zeroed - even ones the host did not actually zero. Add a zeroed_bitmap to page_reporting_dev_info that the report() callback can use to indicate which pages were actually zeroed. The driver's report() callback is responsible for managing the bitmap: zeroing it before sending pages to the host, then setting bits for pages the host actually zeroed. page_reporting_drain() checks the bitmap per-page in addition to the global host_zeroes_pages flag. No driver sets host_zeroes_pages yet, so the static key is off and the bitmap is never read. Behavior is unchanged. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- include/linux/page_reporting.h | 7 +++++++ mm/page_reporting.c | 8 ++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h index c331c6b36687..e2e6a487ddab 100644 --- a/include/linux/page_reporting.h +++ b/include/linux/page_reporting.h @@ -17,6 +17,13 @@ struct page_reporting_dev_info { /* If true, host zeros reported pages on reclaim */ bool host_zeroes_pages; + /* + * Per-page zeroed status, indexed by scatterlist position. + * The driver's report() callback must clear the bitmap, + * then set bits for pages that were actually zeroed. + */ + DECLARE_BITMAP(zeroed_bitmap, PAGE_REPORTING_CAPACITY); + /* work struct for processing reports */ struct delayed_work work; diff --git a/mm/page_reporting.c b/mm/page_reporting.c index 37e4fce9eb38..6c957a9daeef 100644 --- a/mm/page_reporting.c +++ b/mm/page_reporting.c @@ -108,6 +108,7 @@ page_reporting_drain(struct page_reporting_dev_info *prdev, struct scatterlist *sgl, unsigned int nents, bool reported) { struct scatterlist *sg = sgl; + unsigned int i = 0; /* * Drain the now reported pages back into their respective @@ -122,7 +123,7 @@ page_reporting_drain(struct page_reporting_dev_info *prdev, /* If the pages were not reported due to error skip flagging */ if (!reported) - continue; + goto next; /* * If page was not commingled with another page we can @@ -133,9 +134,12 @@ page_reporting_drain(struct page_reporting_dev_info *prdev, */ if (PageBuddy(page) && buddy_order(page) == order) { __SetPageReported(page); - if (page_reporting_host_zeroes_pages()) + if (page_reporting_host_zeroes_pages() && + test_bit(i, prdev->zeroed_bitmap)) __SetPageZeroed(page); } +next: + i++; } while ((sg = sg_next(sg))); /* reinitialize scatterlist now that it is empty */ -- MST