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 <[email protected]> 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
