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Tsirkin" , Jason Wang Subject: [PULL 13/24] vhost: add vhost_svq_poll Date: Tue, 19 Jul 2022 21:16:26 +0800 Message-Id: <20220719131637.46131-14-jasowang@redhat.com> In-Reply-To: <20220719131637.46131-1-jasowang@redhat.com> References: <20220719131637.46131-1-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 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=170.10.129.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 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_LOW=-0.7, 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: 1658237604094100001 From: Eugenio P=C3=A9rez It allows the Shadow Control VirtQueue to wait for the device to use the available buffers. Signed-off-by: Eugenio P=C3=A9rez Reviewed-by: Michael S. Tsirkin Signed-off-by: Jason Wang --- hw/virtio/vhost-shadow-virtqueue.c | 27 +++++++++++++++++++++++++++ hw/virtio/vhost-shadow-virtqueue.h | 1 + 2 files changed, 28 insertions(+) diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-vi= rtqueue.c index c3a75ca..cc2ee47 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -486,6 +486,33 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq, } =20 /** + * Poll the SVQ for one device used buffer. + * + * This function race with main event loop SVQ polling, so extra + * synchronization is needed. + * + * Return the length written by the device. + */ +size_t vhost_svq_poll(VhostShadowVirtqueue *svq) +{ + int64_t start_us =3D g_get_monotonic_time(); + do { + uint32_t len; + VirtQueueElement *elem =3D vhost_svq_get_buf(svq, &len); + if (elem) { + return len; + } + + if (unlikely(g_get_monotonic_time() - start_us > 10e6)) { + return 0; + } + + /* Make sure we read new used_idx */ + smp_rmb(); + } while (true); +} + +/** * Forward used buffers. * * @n: hdev call event notifier, the one that device set to notify svq. diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-vi= rtqueue.h index dd78f4b..cf442f7 100644 --- a/hw/virtio/vhost-shadow-virtqueue.h +++ b/hw/virtio/vhost-shadow-virtqueue.h @@ -89,6 +89,7 @@ void vhost_svq_push_elem(VhostShadowVirtqueue *svq, int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg, size_t out_num, const struct iovec *in_sg, size_t in_num, VirtQueueElement *elem); +size_t vhost_svq_poll(VhostShadowVirtqueue *svq); =20 void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd); void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd); --=20 2.7.4