Message ID | 850cd20b072cd330cb24aa1c92732b9722998d40.1696477105.git.mst@redhat.com |
---|---|
State | New |
Headers | show
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Tsirkin" <mst@redhat.com> To: qemu-devel@nongnu.org Cc: Peter Maydell <peter.maydell@linaro.org>, Ilya Maximets <i.maximets@ovn.org>, Stefan Hajnoczi <stefanha@redhat.com> Subject: [PULL v2 47/53] virtio: use shadow_avail_idx while checking number of heads Message-ID: <850cd20b072cd330cb24aa1c92732b9722998d40.1696477105.git.mst@redhat.com> References: <cover.1696477105.git.mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <cover.1696477105.git.mst@redhat.com> X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: <qemu-devel.nongnu.org> List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>, <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe> List-Archive: <https://lists.nongnu.org/archive/html/qemu-devel> List-Post: <mailto:qemu-devel@nongnu.org> List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help> List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>, <mailto:qemu-devel-request@nongnu.org?subject=subscribe> Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org |
Series |
[PULL,v2,01/53] pci: SLT must be RO
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expand
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diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index c727e9201b..2058b838e9 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -997,7 +997,12 @@ void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem, /* Called within rcu_read_lock(). */ static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx) { - uint16_t num_heads = vring_avail_idx(vq) - idx; + uint16_t avail_idx, num_heads; + + /* Use shadow index whenever possible. */ + avail_idx = (vq->shadow_avail_idx != idx) ? vq->shadow_avail_idx + : vring_avail_idx(vq); + num_heads = avail_idx - idx; /* Check it isn't doing very strange things with descriptor numbers. */ if (num_heads > vq->vring.num) { @@ -1005,8 +1010,15 @@ static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx) idx, vq->shadow_avail_idx); return -EINVAL; } - /* On success, callers read a descriptor at vq->last_avail_idx. - * Make sure descriptor read does not bypass avail index read. */ + /* + * On success, callers read a descriptor at vq->last_avail_idx. + * Make sure descriptor read does not bypass avail index read. + * + * This is necessary even if we are using a shadow index, since + * the shadow index could have been initialized by calling + * vring_avail_idx() outside of this function, i.e., by a guest + * memory read not accompanied by a barrier. + */ if (num_heads) { smp_rmb(); }