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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4548ec6b071sm23711514f8f.14.2026.05.11.02.03.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 02:03:35 -0700 (PDT) Date: Mon, 11 May 2026 05:03:30 -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. 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Howlett" Subject: [PATCH resend v6 19/30] mm: page_reporting: add per-page zeroed bitmap for host feedback Message-ID: 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: KSk-uuifPCRMday4c_SSxUwQQ3WFGkLUBwQbl8jGhNA_1778490216 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 55562C0002 X-Stat-Signature: ckgsne7qpr8t41irpwo76778gpa1hopm X-Rspam-User: X-HE-Tag: 1778490220-313238 X-HE-Meta: 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 JB6ppVzy v6Ztte4L58kWaWEknrgFqc1ajUnJSoxKgzxBRmzKUUHwg84VxrvbWn9+nc2njfLFBeagWX/k0h6x5FxoMmdcLFak9gJ/CmxKnvfSHmqxy8F8tOgQUY1PrMtEbexr920cmqNnaVfOKnW1wUF436d622q2iAbx9JfKOkSJ52MP+CUuAZiZr67dxmNSh3vyX9HNRGgyyfKZgJFJEyHSmpD/8d7rOPsbnGXbmbtddr0sJd+VGmC5Ne9b9pOEokLBPz+yz5UZk7pv6ZQ7ssxcoP26auAnCbbn1m5fKluI+GEiccNeLJIdGaqVo0/VtRtVby27zYuRJxKmXf05vzSkEA+b2PBqR0uMxoMU/0wJhwOHqtrxuihFUZqRB95aG4xogb/K0L6okVH4SdNDBgH9fia1LSv/6WPgu1aS9nuqNmRQ1RtHmVZfSx9rcaaseGMtyU+ZYeq4g 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