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bh=dMW7XSrsfgp8nboBmYNgB/lE8SOueE180TTHvJLYef8=; b=EXzplAGvdMc4fdf6ZllMk4C65Cn7SaBHYZRj+pRkKfai7I23FyUsib4877ZYCKtjbSOaz4 h9jFPsl0uMtF4/eoaq+SIxIa6HurBuQhXMHbHA9RlB/lM75QQjQZ/bXPZjtPt4o13qhjQO gDsf2thq5uMoMtVgWXIecIqGmVWiWFk= X-MC-Unique: NnMFuWFxOhO800dj8PeUtg-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org Subject: [PULL 15/33] virtio-scsi: replace AioContext lock with tmf_bh_lock Date: Thu, 21 Dec 2023 22:23:20 +0100 Message-ID: <20231221212339.164439-16-kwolf@redhat.com> In-Reply-To: <20231221212339.164439-1-kwolf@redhat.com> References: <20231221212339.164439-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 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=kwolf@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=-0.061, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1703194123772100005 Content-Type: text/plain; charset="utf-8" From: Stefan Hajnoczi Protect the Task Management Function BH state with a lock. The TMF BH runs in the main loop thread. An IOThread might process a TMF at the same time as the TMF BH is running. Therefore tmf_bh_list and tmf_bh must be protected by a lock. Run TMF request completion in the IOThread using aio_wait_bh_oneshot(). This avoids more locking to protect the virtqueue and SCSI layer state. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf Message-ID: <20231205182011.1976568-2-stefanha@redhat.com> Signed-off-by: Kevin Wolf --- include/hw/virtio/virtio-scsi.h | 3 +- hw/scsi/virtio-scsi.c | 62 ++++++++++++++++++++++----------- 2 files changed, 43 insertions(+), 22 deletions(-) diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scs= i.h index 779568ab5d..da8cb928d9 100644 --- a/include/hw/virtio/virtio-scsi.h +++ b/include/hw/virtio/virtio-scsi.h @@ -85,8 +85,9 @@ struct VirtIOSCSI { =20 /* * TMFs deferred to main loop BH. These fields are protected by - * virtio_scsi_acquire(). + * tmf_bh_lock. */ + QemuMutex tmf_bh_lock; QEMUBH *tmf_bh; QTAILQ_HEAD(, VirtIOSCSIReq) tmf_bh_list; =20 diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index 9c751bf296..4f8d35facc 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -123,6 +123,30 @@ static void virtio_scsi_complete_req(VirtIOSCSIReq *re= q) virtio_scsi_free_req(req); } =20 +static void virtio_scsi_complete_req_bh(void *opaque) +{ + VirtIOSCSIReq *req =3D opaque; + + virtio_scsi_complete_req(req); +} + +/* + * Called from virtio_scsi_do_one_tmf_bh() in main loop thread. The main l= oop + * thread cannot touch the virtqueue since that could race with an IOThrea= d. + */ +static void virtio_scsi_complete_req_from_main_loop(VirtIOSCSIReq *req) +{ + VirtIOSCSI *s =3D req->dev; + + if (!s->ctx || s->ctx =3D=3D qemu_get_aio_context()) { + /* No need to schedule a BH when there is no IOThread */ + virtio_scsi_complete_req(req); + } else { + /* Run request completion in the IOThread */ + aio_wait_bh_oneshot(s->ctx, virtio_scsi_complete_req_bh, req); + } +} + static void virtio_scsi_bad_req(VirtIOSCSIReq *req) { virtio_error(VIRTIO_DEVICE(req->dev), "wrong size for virtio-scsi head= ers"); @@ -338,10 +362,7 @@ static void virtio_scsi_do_one_tmf_bh(VirtIOSCSIReq *r= eq) =20 out: object_unref(OBJECT(d)); - - virtio_scsi_acquire(s); - virtio_scsi_complete_req(req); - virtio_scsi_release(s); + virtio_scsi_complete_req_from_main_loop(req); } =20 /* Some TMFs must be processed from the main loop thread */ @@ -354,18 +375,16 @@ static void virtio_scsi_do_tmf_bh(void *opaque) =20 GLOBAL_STATE_CODE(); =20 - virtio_scsi_acquire(s); + WITH_QEMU_LOCK_GUARD(&s->tmf_bh_lock) { + QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) { + QTAILQ_REMOVE(&s->tmf_bh_list, req, next); + QTAILQ_INSERT_TAIL(&reqs, req, next); + } =20 - QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) { - QTAILQ_REMOVE(&s->tmf_bh_list, req, next); - QTAILQ_INSERT_TAIL(&reqs, req, next); + qemu_bh_delete(s->tmf_bh); + s->tmf_bh =3D NULL; } =20 - qemu_bh_delete(s->tmf_bh); - s->tmf_bh =3D NULL; - - virtio_scsi_release(s); - QTAILQ_FOREACH_SAFE(req, &reqs, next, tmp) { QTAILQ_REMOVE(&reqs, req, next); virtio_scsi_do_one_tmf_bh(req); @@ -379,8 +398,7 @@ static void virtio_scsi_reset_tmf_bh(VirtIOSCSI *s) =20 GLOBAL_STATE_CODE(); =20 - virtio_scsi_acquire(s); - + /* Called after ioeventfd has been stopped, so tmf_bh_lock is not need= ed */ if (s->tmf_bh) { qemu_bh_delete(s->tmf_bh); s->tmf_bh =3D NULL; @@ -393,19 +411,19 @@ static void virtio_scsi_reset_tmf_bh(VirtIOSCSI *s) req->resp.tmf.response =3D VIRTIO_SCSI_S_TARGET_FAILURE; virtio_scsi_complete_req(req); } - - virtio_scsi_release(s); } =20 static void virtio_scsi_defer_tmf_to_bh(VirtIOSCSIReq *req) { VirtIOSCSI *s =3D req->dev; =20 - QTAILQ_INSERT_TAIL(&s->tmf_bh_list, req, next); + WITH_QEMU_LOCK_GUARD(&s->tmf_bh_lock) { + QTAILQ_INSERT_TAIL(&s->tmf_bh_list, req, next); =20 - if (!s->tmf_bh) { - s->tmf_bh =3D qemu_bh_new(virtio_scsi_do_tmf_bh, s); - qemu_bh_schedule(s->tmf_bh); + if (!s->tmf_bh) { + s->tmf_bh =3D qemu_bh_new(virtio_scsi_do_tmf_bh, s); + qemu_bh_schedule(s->tmf_bh); + } } } =20 @@ -1235,6 +1253,7 @@ static void virtio_scsi_device_realize(DeviceState *d= ev, Error **errp) Error *err =3D NULL; =20 QTAILQ_INIT(&s->tmf_bh_list); + qemu_mutex_init(&s->tmf_bh_lock); =20 virtio_scsi_common_realize(dev, virtio_scsi_handle_ctrl, @@ -1277,6 +1296,7 @@ static void virtio_scsi_device_unrealize(DeviceState = *dev) =20 qbus_set_hotplug_handler(BUS(&s->bus), NULL); virtio_scsi_common_unrealize(dev); + qemu_mutex_destroy(&s->tmf_bh_lock); } =20 static Property virtio_scsi_properties[] =3D { --=20 2.43.0