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Tsirkin" , Laurent Vivier , Cornelia Huck , Cindy Lu , Jason Wang , Liuxiangdong , Zhu Lingshan Subject: [PATCH v5 03/10] vhost: Do not depend on !NULL VirtQueueElement on vhost_svq_flush Date: Tue, 2 Aug 2022 19:57:24 +0200 Message-Id: <20220802175731.312115-4-eperezma@redhat.com> In-Reply-To: <20220802175731.312115-1-eperezma@redhat.com> References: <20220802175731.312115-1-eperezma@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=eperezma@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1659463623146100001 Since QEMU will be able to inject new elements on CVQ to restore the state, we need not to depend on a VirtQueueElement to know if a new element has been used by the device or not. Instead of check that, check if there are new elements only using used idx on vhost_svq_flush. Signed-off-by: Eugenio P=C3=A9rez --- hw/virtio/vhost-shadow-virtqueue.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-vi= rtqueue.c index e6eebd0e8d..fdb550c31b 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -491,7 +491,7 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq, /** * Poll the SVQ for one device used buffer. * - * This function race with main event loop SVQ polling, so extra + * This function races with main event loop SVQ polling, so extra * synchronization is needed. * * Return the length written by the device. @@ -499,20 +499,20 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq, size_t vhost_svq_poll(VhostShadowVirtqueue *svq) { int64_t start_us =3D g_get_monotonic_time(); - do { + while (true) { uint32_t len; - VirtQueueElement *elem =3D vhost_svq_get_buf(svq, &len); - if (elem) { - return len; - } =20 if (unlikely(g_get_monotonic_time() - start_us > 10e6)) { return 0; } =20 - /* Make sure we read new used_idx */ - smp_rmb(); - } while (true); + if (!vhost_svq_more_used(svq)) { + continue; + } + + vhost_svq_get_buf(svq, &len); + return len; + } } =20 /** --=20 2.31.1