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[80.230.47.179]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-489207ebd3asm254796095e9.6.2026.04.26.14.48.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Apr 2026 14:48:29 -0700 (PDT) Date: Sun, 26 Apr 2026 17:48:27 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , Gregory Price , linux-mm@kvack.org, virtualization@lists.linux.dev, Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= Subject: [PATCH RFC v4 18/22] virtio_balloon: a hack to enable host-zeroed page optimization Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Add a module parameter host_zeroes_pages to opt in to the zeroed page optimization. A proper virtio feature flag is needed before this can be merged. insmod virtio_balloon.ko host_zeroes_pages=1 Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- drivers/virtio/virtio_balloon.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index d1fbc8fe8470..8c15530b51b3 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -19,6 +19,11 @@ #include #include +static bool host_zeroes_pages; +module_param(host_zeroes_pages, bool, 0444); +MODULE_PARM_DESC(host_zeroes_pages, + "Host zeroes reported pages, skip guest re-zeroing"); + /* * Balloon device works in 4K page units. So each page is pointed to by * multiple balloon pages. All memory counters in this driver are in balloon @@ -204,6 +209,8 @@ static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_i struct virtqueue *vq = vb->reporting_vq; unsigned int unused, err; + bitmap_zero(pr_dev_info->zeroed_bitmap, nents); + /* We should always be able to add these buffers to an empty queue. */ err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT); @@ -220,6 +227,9 @@ static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_i /* When host has read buffer, this completes via balloon_ack */ wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); + if (host_zeroes_pages) + bitmap_fill(pr_dev_info->zeroed_bitmap, nents); + return 0; } @@ -1039,6 +1049,8 @@ static int virtballoon_probe(struct virtio_device *vdev) vb->pr_dev_info.order = 5; #endif + /* TODO: needs a virtio feature flag */ + vb->pr_dev_info.host_zeroes_pages = host_zeroes_pages; err = page_reporting_register(&vb->pr_dev_info); if (err) goto out_unregister_oom; -- MST