From mboxrd@z Thu Jan 1 00:00:00 1970 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 C13ECC77B7C for ; Thu, 4 May 2023 21:26:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pugSE-0008Vv-Mx; Thu, 04 May 2023 17:25:34 -0400 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 1pugSD-0008VL-55 for qemu-devel@nongnu.org; Thu, 04 May 2023 17:25:33 -0400 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 1pugSB-0003mI-GZ for qemu-devel@nongnu.org; Thu, 04 May 2023 17:25:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683235526; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EXBTvckOEwAXoXWbpnPFajVuZsPXxwBJqTqoZHV9JvQ=; b=LwCDJtdyWLZA3JVOSPOIeAXl/ZUD1kgOc4Lza7nDs26nCJ9MF70UYJFeGo24EDRSLvlOv5 S2zC9g9M6xfWbvcQlH8epki8No3YMh73QaY4Ibwkh+EazYQ4YRdU5nQpLnIIwzQHgKPgZ8 O4bR8X0YGQFItSbTy+hHc6sAS8t66P8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-365-0JHXhtIDOzGjIqozYKIm0A-1; Thu, 04 May 2023 17:25:23 -0400 X-MC-Unique: 0JHXhtIDOzGjIqozYKIm0A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BB301185A78B; Thu, 4 May 2023 21:25:22 +0000 (UTC) Received: from redhat.com (unknown [10.39.192.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1EA6640C2064; Thu, 4 May 2023 21:25:18 +0000 (UTC) Date: Thu, 4 May 2023 23:25:17 +0200 From: Kevin Wolf To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Juan Quintela , Julia Suvorova , xen-devel@lists.xenproject.org, eesposit@redhat.com, Richard Henderson , Fam Zheng , "Michael S. Tsirkin" , Coiby Xu , David Woodhouse , Marcel Apfelbaum , Peter Lieven , Paul Durrant , "Richard W.M. Jones" , qemu-block@nongnu.org, Stefano Garzarella , Anthony Perard , Stefan Weil , Xie Yongji , Paolo Bonzini , Aarushi Mehta , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Eduardo Habkost , Stefano Stabellini , Hanna Reitz , Ronnie Sahlberg Subject: Re: [PATCH v4 18/20] virtio-scsi: implement BlockDevOps->drained_begin() Message-ID: References: <20230425172716.1033562-1-stefanha@redhat.com> <20230425172716.1033562-19-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230425172716.1033562-19-stefanha@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.161, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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 Am 25.04.2023 um 19:27 hat Stefan Hajnoczi geschrieben: > The virtio-scsi Host Bus Adapter provides access to devices on a SCSI > bus. Those SCSI devices typically have a BlockBackend. When the > BlockBackend enters a drained section, the SCSI device must temporarily > stop submitting new I/O requests. > > Implement this behavior by temporarily stopping virtio-scsi virtqueue > processing when one of the SCSI devices enters a drained section. The > new scsi_device_drained_begin() API allows scsi-disk to message the > virtio-scsi HBA. > > scsi_device_drained_begin() uses a drain counter so that multiple SCSI > devices can have overlapping drained sections. The HBA only sees one > pair of .drained_begin/end() calls. > > After this commit, virtio-scsi no longer depends on hw/virtio's > ioeventfd aio_set_event_notifier(is_external=true). This commit is a > step towards removing the aio_disable_external() API. > > Signed-off-by: Stefan Hajnoczi > @@ -206,9 +208,11 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev) > } > s->dataplane_stopping = true; > > - aio_context_acquire(s->ctx); > - aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s); > - aio_context_release(s->ctx); > + if (s->bus.drain_count == 0) { > + aio_context_acquire(s->ctx); > + aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s); > + aio_context_release(s->ctx); > + } Same question as for virtio-blk: We lose processing the virtqueue one last time during drain. Is it okay, and if so, why do we need it outside of drain? Kevin