From patchwork Mon Dec 4 16:42:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13478773 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 53F89C4167B for ; Mon, 4 Dec 2023 16:44:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rAC2l-0005fk-Db; Mon, 04 Dec 2023 11:43:39 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2k-0005fZ-9n for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:38 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2e-0003eP-Ud for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701708212; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+gS+ert4RnNDTMYWvrH77lBFagDngb6vqP+jFNgcaJM=; b=R2P29t/vejxO++rrp8u3iykbcyHXaNqnoIc+0XNpF3kyn4pusko8aXSpzbi+KuzIIgwH+s 8KOKYtfwjvmO1/D7ALwtLqihUhV2/X+u4H+ZFZ1zw/4ldbR5kGLYuZ9xDD+288uZH9t3e9 YZ48KAybhGzIP3B7DzhUwBmUilD3Cjo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-582-JOQ-3Ip-NKyKMZ8EcNjfwA-1; Mon, 04 Dec 2023 11:43:30 -0500 X-MC-Unique: JOQ-3Ip-NKyKMZ8EcNjfwA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1A50D85A5B5; Mon, 4 Dec 2023 16:43:30 +0000 (UTC) Received: from localhost (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6BF56492BFC; Mon, 4 Dec 2023 16:43:29 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Peter Xu , "Michael S. Tsirkin" , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , David Hildenbrand , Paolo Bonzini , Fam Zheng , Stefan Hajnoczi , Eric Blake Subject: [PATCH v2 1/4] scsi: only access SCSIDevice->requests from one thread Date: Mon, 4 Dec 2023 11:42:56 -0500 Message-ID: <20231204164259.1515217-2-stefanha@redhat.com> In-Reply-To: <20231204164259.1515217-1-stefanha@redhat.com> References: <20231204164259.1515217-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Stop depending on the AioContext lock and instead access SCSIDevice->requests from only one thread at a time: - When the VM is running only the BlockBackend's AioContext may access the requests list. - When the VM is stopped only the main loop may access the requests list. These constraints protect the requests list without the need for locking in the I/O code path. Note that multiple IOThreads are not supported yet because the code assumes all SCSIRequests are executed from a single AioContext. Leave that as future work. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake --- include/hw/scsi/scsi.h | 7 +- hw/scsi/scsi-bus.c | 180 ++++++++++++++++++++++++++++------------- 2 files changed, 130 insertions(+), 57 deletions(-) diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h index 3692ca82f3..10c4e8288d 100644 --- a/include/hw/scsi/scsi.h +++ b/include/hw/scsi/scsi.h @@ -69,14 +69,19 @@ struct SCSIDevice { DeviceState qdev; VMChangeStateEntry *vmsentry; - QEMUBH *bh; uint32_t id; BlockConf conf; SCSISense unit_attention; bool sense_is_ua; uint8_t sense[SCSI_SENSE_BUF_SIZE]; uint32_t sense_len; + + /* + * The requests list is only accessed from the AioContext that executes + * requests or from the main loop when IOThread processing is stopped. + */ QTAILQ_HEAD(, SCSIRequest) requests; + uint32_t channel; uint32_t lun; int blocksize; diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c index fc4b77fdb0..f3ec11f892 100644 --- a/hw/scsi/scsi-bus.c +++ b/hw/scsi/scsi-bus.c @@ -85,6 +85,88 @@ SCSIDevice *scsi_device_get(SCSIBus *bus, int channel, int id, int lun) return d; } +/* + * Invoke @fn() for each enqueued request in device @s. Must be called from the + * main loop thread while the guest is stopped. This is only suitable for + * vmstate ->put(), use scsi_device_for_each_req_async() for other cases. + */ +static void scsi_device_for_each_req_sync(SCSIDevice *s, + void (*fn)(SCSIRequest *, void *), + void *opaque) +{ + SCSIRequest *req; + SCSIRequest *next_req; + + assert(!runstate_is_running()); + assert(qemu_in_main_thread()); + + QTAILQ_FOREACH_SAFE(req, &s->requests, next, next_req) { + fn(req, opaque); + } +} + +typedef struct { + SCSIDevice *s; + void (*fn)(SCSIRequest *, void *); + void *fn_opaque; +} SCSIDeviceForEachReqAsyncData; + +static void scsi_device_for_each_req_async_bh(void *opaque) +{ + g_autofree SCSIDeviceForEachReqAsyncData *data = opaque; + SCSIDevice *s = data->s; + AioContext *ctx; + SCSIRequest *req; + SCSIRequest *next; + + /* + * If the AioContext changed before this BH was called then reschedule into + * the new AioContext before accessing ->requests. This can happen when + * scsi_device_for_each_req_async() is called and then the AioContext is + * changed before BHs are run. + */ + ctx = blk_get_aio_context(s->conf.blk); + if (ctx != qemu_get_current_aio_context()) { + aio_bh_schedule_oneshot(ctx, scsi_device_for_each_req_async_bh, data); + return; + } + + QTAILQ_FOREACH_SAFE(req, &s->requests, next, next) { + data->fn(req, data->fn_opaque); + } + + /* Drop the reference taken by scsi_device_for_each_req_async() */ + object_unref(OBJECT(s)); +} + +/* + * Schedule @fn() to be invoked for each enqueued request in device @s. @fn() + * runs in the AioContext that is executing the request. + */ +static void scsi_device_for_each_req_async(SCSIDevice *s, + void (*fn)(SCSIRequest *, void *), + void *opaque) +{ + assert(qemu_in_main_thread()); + + SCSIDeviceForEachReqAsyncData *data = + g_new(SCSIDeviceForEachReqAsyncData, 1); + + data->s = s; + data->fn = fn; + data->fn_opaque = opaque; + + /* + * Hold a reference to the SCSIDevice until + * scsi_device_for_each_req_async_bh() finishes. + */ + object_ref(OBJECT(s)); + + aio_bh_schedule_oneshot(blk_get_aio_context(s->conf.blk), + scsi_device_for_each_req_async_bh, + data); +} + static void scsi_device_realize(SCSIDevice *s, Error **errp) { SCSIDeviceClass *sc = SCSI_DEVICE_GET_CLASS(s); @@ -144,20 +226,18 @@ void scsi_bus_init_named(SCSIBus *bus, size_t bus_size, DeviceState *host, qbus_set_bus_hotplug_handler(BUS(bus)); } -static void scsi_dma_restart_bh(void *opaque) +void scsi_req_retry(SCSIRequest *req) { - SCSIDevice *s = opaque; - SCSIRequest *req, *next; + req->retry = true; +} - qemu_bh_delete(s->bh); - s->bh = NULL; - - aio_context_acquire(blk_get_aio_context(s->conf.blk)); - QTAILQ_FOREACH_SAFE(req, &s->requests, next, next) { - scsi_req_ref(req); - if (req->retry) { - req->retry = false; - switch (req->cmd.mode) { +/* Called in the AioContext that is executing the request */ +static void scsi_dma_restart_req(SCSIRequest *req, void *opaque) +{ + scsi_req_ref(req); + if (req->retry) { + req->retry = false; + switch (req->cmd.mode) { case SCSI_XFER_FROM_DEV: case SCSI_XFER_TO_DEV: scsi_req_continue(req); @@ -166,37 +246,22 @@ static void scsi_dma_restart_bh(void *opaque) scsi_req_dequeue(req); scsi_req_enqueue(req); break; - } } - scsi_req_unref(req); } - aio_context_release(blk_get_aio_context(s->conf.blk)); - /* Drop the reference that was acquired in scsi_dma_restart_cb */ - object_unref(OBJECT(s)); -} - -void scsi_req_retry(SCSIRequest *req) -{ - /* No need to save a reference, because scsi_dma_restart_bh just - * looks at the request list. */ - req->retry = true; + scsi_req_unref(req); } static void scsi_dma_restart_cb(void *opaque, bool running, RunState state) { SCSIDevice *s = opaque; + assert(qemu_in_main_thread()); + if (!running) { return; } - if (!s->bh) { - AioContext *ctx = blk_get_aio_context(s->conf.blk); - /* The reference is dropped in scsi_dma_restart_bh.*/ - object_ref(OBJECT(s)); - s->bh = aio_bh_new_guarded(ctx, scsi_dma_restart_bh, s, - &DEVICE(s)->mem_reentrancy_guard); - qemu_bh_schedule(s->bh); - } + + scsi_device_for_each_req_async(s, scsi_dma_restart_req, NULL); } static bool scsi_bus_is_address_free(SCSIBus *bus, @@ -1657,15 +1722,16 @@ void scsi_device_set_ua(SCSIDevice *sdev, SCSISense sense) } } +static void scsi_device_purge_one_req(SCSIRequest *req, void *opaque) +{ + scsi_req_cancel_async(req, NULL); +} + void scsi_device_purge_requests(SCSIDevice *sdev, SCSISense sense) { - SCSIRequest *req; + scsi_device_for_each_req_async(sdev, scsi_device_purge_one_req, NULL); aio_context_acquire(blk_get_aio_context(sdev->conf.blk)); - while (!QTAILQ_EMPTY(&sdev->requests)) { - req = QTAILQ_FIRST(&sdev->requests); - scsi_req_cancel_async(req, NULL); - } blk_drain(sdev->conf.blk); aio_context_release(blk_get_aio_context(sdev->conf.blk)); scsi_device_set_ua(sdev, sense); @@ -1737,31 +1803,33 @@ static char *scsibus_get_fw_dev_path(DeviceState *dev) /* SCSI request list. For simplicity, pv points to the whole device */ +static void put_scsi_req(SCSIRequest *req, void *opaque) +{ + QEMUFile *f = opaque; + + assert(!req->io_canceled); + assert(req->status == -1 && req->host_status == -1); + assert(req->enqueued); + + qemu_put_sbyte(f, req->retry ? 1 : 2); + qemu_put_buffer(f, req->cmd.buf, sizeof(req->cmd.buf)); + qemu_put_be32s(f, &req->tag); + qemu_put_be32s(f, &req->lun); + if (req->bus->info->save_request) { + req->bus->info->save_request(f, req); + } + if (req->ops->save_request) { + req->ops->save_request(f, req); + } +} + static int put_scsi_requests(QEMUFile *f, void *pv, size_t size, const VMStateField *field, JSONWriter *vmdesc) { SCSIDevice *s = pv; - SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, s->qdev.parent_bus); - SCSIRequest *req; - QTAILQ_FOREACH(req, &s->requests, next) { - assert(!req->io_canceled); - assert(req->status == -1 && req->host_status == -1); - assert(req->enqueued); - - qemu_put_sbyte(f, req->retry ? 1 : 2); - qemu_put_buffer(f, req->cmd.buf, sizeof(req->cmd.buf)); - qemu_put_be32s(f, &req->tag); - qemu_put_be32s(f, &req->lun); - if (bus->info->save_request) { - bus->info->save_request(f, req); - } - if (req->ops->save_request) { - req->ops->save_request(f, req); - } - } + scsi_device_for_each_req_sync(s, put_scsi_req, f); qemu_put_sbyte(f, 0); - return 0; } From patchwork Mon Dec 4 16:42:57 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13478774 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5F824C4167B for ; Mon, 4 Dec 2023 16:44:39 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rAC2r-0005gw-5x; Mon, 04 Dec 2023 11:43:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2m-0005g8-Gr for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2l-0003f0-0c for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701708216; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=etFa0T/3g4Vz8zVD5Uqj12qgEaaNIPMHbzLF/3mOxAg=; b=J0ioj019B2fcSRLG/Vr6XxUTDbWRU1WpmDrPiVDS5wwG6oYI9aoNZPIMWyaujXTJUiKUkq lscgDck6rE28jwMPLW7jWNbnXNODsy8q45OnhyK+nd2bMM4NCjPYnASZJF4N3FssbXhnQU PJxGmyQYq1jthXI2/S+NLXEh2z7gObU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-317-uCOf092HMb6_efvT289IDw-1; Mon, 04 Dec 2023 11:43:33 -0500 X-MC-Unique: uCOf092HMb6_efvT289IDw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F3FE481C97E; Mon, 4 Dec 2023 16:43:32 +0000 (UTC) Received: from localhost (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7A6711C060BD; Mon, 4 Dec 2023 16:43:31 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Peter Xu , "Michael S. Tsirkin" , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , David Hildenbrand , Paolo Bonzini , Fam Zheng , Stefan Hajnoczi , Eric Blake , Kevin Wolf Subject: [PATCH v2 2/4] virtio-scsi: don't lock AioContext around virtio_queue_aio_attach_host_notifier() Date: Mon, 4 Dec 2023 11:42:57 -0500 Message-ID: <20231204164259.1515217-3-stefanha@redhat.com> In-Reply-To: <20231204164259.1515217-1-stefanha@redhat.com> References: <20231204164259.1515217-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@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, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org virtio_queue_aio_attach_host_notifier() does not require the AioContext lock. Stop taking the lock and add an explicit smp_wmb() because we were relying on the implicit barrier in the AioContext lock before. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf --- hw/scsi/virtio-scsi-dataplane.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c index 1e684beebe..135e23fe54 100644 --- a/hw/scsi/virtio-scsi-dataplane.c +++ b/hw/scsi/virtio-scsi-dataplane.c @@ -149,23 +149,17 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev) memory_region_transaction_commit(); - /* - * These fields are visible to the IOThread so we rely on implicit barriers - * in aio_context_acquire() on the write side and aio_notify_accept() on - * the read side. - */ s->dataplane_starting = false; s->dataplane_started = true; + smp_wmb(); /* paired with aio_notify_accept() */ if (s->bus.drain_count == 0) { - aio_context_acquire(s->ctx); virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx); virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx); for (i = 0; i < vs->conf.num_queues; i++) { virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx); } - aio_context_release(s->ctx); } return 0; From patchwork Mon Dec 4 16:42:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13478772 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8F013C46CA3 for ; Mon, 4 Dec 2023 16:43:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rAC2q-0005gI-DF; Mon, 04 Dec 2023 11:43:44 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2m-0005g0-9V for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2k-0003f5-D2 for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701708217; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M01/+fvDQjp6kt3/6ISyyy24SEKAvMPqn4iykM3d3Y8=; b=A/RaVLE+6IVxxtPx0RECPHgfJTkigDSj2D5d/t6zD5Tu+mo+tkmKGdCqpszA2tdlhFXnEe z50IXJ8IlSm0DybCavXTU7Umfkt1WEV1u7vjCQ62Ciwz5FKod6QIO+2PkseUQ44tu5v57P CU7MoTH8xgU4TukvIp+HsI2BHYWEJxY= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-66-6tkQak11Oxup0hGxrmW_iw-1; Mon, 04 Dec 2023 11:43:36 -0500 X-MC-Unique: 6tkQak11Oxup0hGxrmW_iw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 092FD1C068DE; Mon, 4 Dec 2023 16:43:36 +0000 (UTC) Received: from localhost (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5F8C12026D68; Mon, 4 Dec 2023 16:43:35 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Peter Xu , "Michael S. Tsirkin" , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , David Hildenbrand , Paolo Bonzini , Fam Zheng , Stefan Hajnoczi , Eric Blake , Kevin Wolf Subject: [PATCH v2 3/4] scsi: don't lock AioContext in I/O code path Date: Mon, 4 Dec 2023 11:42:58 -0500 Message-ID: <20231204164259.1515217-4-stefanha@redhat.com> In-Reply-To: <20231204164259.1515217-1-stefanha@redhat.com> References: <20231204164259.1515217-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@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_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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org blk_aio_*() doesn't require the AioContext lock and the SCSI subsystem's internal state also does not anymore. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Acked-by: Kevin Wolf --- hw/scsi/scsi-disk.c | 23 ----------------------- hw/scsi/scsi-generic.c | 20 +++----------------- 2 files changed, 3 insertions(+), 40 deletions(-) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index 6691f5edb8..2c1bbb3530 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -273,8 +273,6 @@ static void scsi_aio_complete(void *opaque, int ret) SCSIDiskReq *r = (SCSIDiskReq *)opaque; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -286,7 +284,6 @@ static void scsi_aio_complete(void *opaque, int ret) scsi_req_complete(&r->req, GOOD); done: - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); scsi_req_unref(&r->req); } @@ -394,8 +391,6 @@ static void scsi_read_complete(void *opaque, int ret) SCSIDiskReq *r = (SCSIDiskReq *)opaque; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -406,7 +401,6 @@ static void scsi_read_complete(void *opaque, int ret) trace_scsi_disk_read_complete(r->req.tag, r->qiov.size); } scsi_read_complete_noio(r, ret); - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); } /* Actually issue a read to the block device. */ @@ -448,8 +442,6 @@ static void scsi_do_read_cb(void *opaque, int ret) SCSIDiskReq *r = (SCSIDiskReq *)opaque; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert (r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -459,7 +451,6 @@ static void scsi_do_read_cb(void *opaque, int ret) block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct); } scsi_do_read(opaque, ret); - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); } /* Read more data from scsi device into buffer. */ @@ -533,8 +524,6 @@ static void scsi_write_complete(void * opaque, int ret) SCSIDiskReq *r = (SCSIDiskReq *)opaque; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert (r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -544,7 +533,6 @@ static void scsi_write_complete(void * opaque, int ret) block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct); } scsi_write_complete_noio(r, ret); - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); } static void scsi_write_data(SCSIRequest *req) @@ -1742,8 +1730,6 @@ static void scsi_unmap_complete(void *opaque, int ret) SCSIDiskReq *r = data->r; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -1754,7 +1740,6 @@ static void scsi_unmap_complete(void *opaque, int ret) block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct); scsi_unmap_complete_noio(data, ret); } - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); } static void scsi_disk_emulate_unmap(SCSIDiskReq *r, uint8_t *inbuf) @@ -1822,8 +1807,6 @@ static void scsi_write_same_complete(void *opaque, int ret) SCSIDiskReq *r = data->r; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; @@ -1847,7 +1830,6 @@ static void scsi_write_same_complete(void *opaque, int ret) data->sector << BDRV_SECTOR_BITS, &data->qiov, 0, scsi_write_same_complete, data); - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); return; } @@ -1857,7 +1839,6 @@ done: scsi_req_unref(&r->req); qemu_vfree(data->iov.iov_base); g_free(data); - aio_context_release(blk_get_aio_context(s->qdev.conf.blk)); } static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf) @@ -2810,7 +2791,6 @@ static void scsi_block_sgio_complete(void *opaque, int ret) { SCSIBlockReq *req = (SCSIBlockReq *)opaque; SCSIDiskReq *r = &req->req; - SCSIDevice *s = r->req.dev; sg_io_hdr_t *io_hdr = &req->io_header; if (ret == 0) { @@ -2827,13 +2807,10 @@ static void scsi_block_sgio_complete(void *opaque, int ret) } if (ret > 0) { - aio_context_acquire(blk_get_aio_context(s->conf.blk)); if (scsi_handle_rw_error(r, ret, true)) { - aio_context_release(blk_get_aio_context(s->conf.blk)); scsi_req_unref(&r->req); return; } - aio_context_release(blk_get_aio_context(s->conf.blk)); /* Ignore error. */ ret = 0; diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index 2417f0ad84..b7b04e1d63 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -109,15 +109,11 @@ done: static void scsi_command_complete(void *opaque, int ret) { SCSIGenericReq *r = (SCSIGenericReq *)opaque; - SCSIDevice *s = r->req.dev; - - aio_context_acquire(blk_get_aio_context(s->conf.blk)); assert(r->req.aiocb != NULL); r->req.aiocb = NULL; scsi_command_complete_noio(r, ret); - aio_context_release(blk_get_aio_context(s->conf.blk)); } static int execute_command(BlockBackend *blk, @@ -274,14 +270,12 @@ static void scsi_read_complete(void * opaque, int ret) SCSIDevice *s = r->req.dev; int len; - aio_context_acquire(blk_get_aio_context(s->conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; if (ret || r->req.io_canceled) { scsi_command_complete_noio(r, ret); - goto done; + return; } len = r->io_header.dxfer_len - r->io_header.resid; @@ -320,7 +314,7 @@ static void scsi_read_complete(void * opaque, int ret) r->io_header.status != GOOD || len == 0) { scsi_command_complete_noio(r, 0); - goto done; + return; } /* Snoop READ CAPACITY output to set the blocksize. */ @@ -356,9 +350,6 @@ static void scsi_read_complete(void * opaque, int ret) req_complete: scsi_req_data(&r->req, len); scsi_req_unref(&r->req); - -done: - aio_context_release(blk_get_aio_context(s->conf.blk)); } /* Read more data from scsi device into buffer. */ @@ -391,14 +382,12 @@ static void scsi_write_complete(void * opaque, int ret) trace_scsi_generic_write_complete(ret); - aio_context_acquire(blk_get_aio_context(s->conf.blk)); - assert(r->req.aiocb != NULL); r->req.aiocb = NULL; if (ret || r->req.io_canceled) { scsi_command_complete_noio(r, ret); - goto done; + return; } if (r->req.cmd.buf[0] == MODE_SELECT && r->req.cmd.buf[4] == 12 && @@ -408,9 +397,6 @@ static void scsi_write_complete(void * opaque, int ret) } scsi_command_complete_noio(r, ret); - -done: - aio_context_release(blk_get_aio_context(s->conf.blk)); } /* Write data to a scsi device. Returns nonzero on failure. From patchwork Mon Dec 4 16:42:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13478775 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 11F20C4167B for ; Mon, 4 Dec 2023 16:44:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rAC2z-0005it-ES; Mon, 04 Dec 2023 11:43:53 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2v-0005hs-OH for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:49 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rAC2q-0003fv-Br for qemu-devel@nongnu.org; Mon, 04 Dec 2023 11:43:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701708222; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5LFbfzn0uWEVgSJqhghAiPqOrVkXEXPxN7owVjxzB5I=; b=X5vlWXuaVcePhw0rDNCrqBZ03i3WWLNR9Utbt95GuNN41R/6zb92f0sHB4UvpWTN+yC3rz XNyyEe3ayGn9oOPW93KLNZvurY8e/Xb+NC34MyFqyiSHEcesEByFID7JBY0sXS8YfdgQ+1 cTRNflhbfNqi5h0hfezFc+LF4kPNMhI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-152-jTI_Bfl7NjG_vVkWnRiztA-1; Mon, 04 Dec 2023 11:43:38 -0500 X-MC-Unique: jTI_Bfl7NjG_vVkWnRiztA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5F29D101B041; Mon, 4 Dec 2023 16:43:38 +0000 (UTC) Received: from localhost (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6ACDE2166B26; Mon, 4 Dec 2023 16:43:37 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Peter Xu , "Michael S. Tsirkin" , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , David Hildenbrand , Paolo Bonzini , Fam Zheng , Stefan Hajnoczi , Eric Blake , Kevin Wolf Subject: [PATCH v2 4/4] dma-helpers: don't lock AioContext in dma_blk_cb() Date: Mon, 4 Dec 2023 11:42:59 -0500 Message-ID: <20231204164259.1515217-5-stefanha@redhat.com> In-Reply-To: <20231204164259.1515217-1-stefanha@redhat.com> References: <20231204164259.1515217-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@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_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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Commit abfcd2760b3e ("dma-helpers: prevent dma_blk_cb() vs dma_aio_cancel() race") acquired the AioContext lock inside dma_blk_cb() to avoid a race with scsi_device_purge_requests() running in the main loop thread. The SCSI code no longer calls dma_aio_cancel() from the main loop thread while I/O is running in the IOThread AioContext. Therefore it is no longer necessary to take this lock to protect DMAAIOCB fields. The ->cb() function also does not require the lock because blk_aio_*() and friends do not need the AioContext lock. Both hw/ide/core.c and hw/ide/macio.c also call dma_blk_io() but don't rely on it taking the AioContext lock, so this change is safe. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf --- system/dma-helpers.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/system/dma-helpers.c b/system/dma-helpers.c index 36211acc7e..528117f256 100644 --- a/system/dma-helpers.c +++ b/system/dma-helpers.c @@ -119,13 +119,12 @@ static void dma_blk_cb(void *opaque, int ret) trace_dma_blk_cb(dbs, ret); - aio_context_acquire(ctx); dbs->acb = NULL; dbs->offset += dbs->iov.size; if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) { dma_complete(dbs, ret); - goto out; + return; } dma_blk_unmap(dbs); @@ -168,7 +167,7 @@ static void dma_blk_cb(void *opaque, int ret) trace_dma_map_wait(dbs); dbs->bh = aio_bh_new(ctx, reschedule_dma, dbs); cpu_register_map_client(dbs->bh); - goto out; + return; } if (!QEMU_IS_ALIGNED(dbs->iov.size, dbs->align)) { @@ -179,8 +178,6 @@ static void dma_blk_cb(void *opaque, int ret) dbs->acb = dbs->io_func(dbs->offset, &dbs->iov, dma_blk_cb, dbs, dbs->io_func_opaque); assert(dbs->acb); -out: - aio_context_release(ctx); } static void dma_aio_cancel(BlockAIOCB *acb)