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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45412cefd38sm2251262f8f.9.2026.05.07.15.23.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2026 15:23:26 -0700 (PDT) Date: Thu, 7 May 2026 18:23:24 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , virtualization@lists.linux.dev Subject: [PATCH v5 20/28] virtio_balloon: submit reported pages as individual buffers Message-ID: <84a052f6bb0b0e286e9bd0f640e4f7269b1921c4.1778192416.git.mst@redhat.com> 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 Submit each reported page as a separate virtqueue buffer instead of one buffer with an sg list of all pages. This avoids indirect descriptor allocation (kmalloc in the reporting path) and gives per-page used length feedback from the device. On error, the already-queued pages are kicked and drained before the error is returned. The caller (page_reporting_drain) then marks the batch as unreported, which is conservative but correct. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- drivers/virtio/virtio_balloon.c | 36 +++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 13 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 7ed024315539..e99ffbbdd2bd 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -202,25 +202,35 @@ static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_i struct virtio_balloon *vb = container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); struct virtqueue *vq = vb->reporting_vq; - unsigned int unused, err; + unsigned int i, err; /* We should always be able to add these buffers to an empty queue. */ - err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT); + for (i = 0; i < nents; i++) { + struct scatterlist one; - /* - * In the extremely unlikely case that something has occurred and we - * are able to trigger an error we will simply display a warning - * and exit without actually processing the pages. - */ - if (WARN_ON_ONCE(err)) - return err; + sg_init_table(&one, 1); + sg_set_page(&one, sg_page(&sg[i]), sg[i].length, + sg[i].offset); + err = virtqueue_add_inbuf(vq, &one, 1, &sg[i], GFP_NOWAIT); + if (WARN_ON_ONCE(err)) { + nents = i; + break; + } + } - virtqueue_kick(vq); + if (nents) { + virtqueue_kick(vq); - /* When host has read buffer, this completes via balloon_ack */ - wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); + /* When host has read buffer, this completes via balloon_ack */ + for (i = 0; i < nents; i++) { + unsigned int unused; - return 0; + wait_event(vb->acked, + virtqueue_get_buf(vq, &unused)); + } + } + + return err; } static void set_page_pfns(struct virtio_balloon *vb, -- MST