From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43720) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dmiJN-0003l2-O4 for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:20:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dmiJK-0006zL-J3 for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:20:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52684) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dmiJK-0006yw-9N for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:20:14 -0400 Date: Tue, 29 Aug 2017 18:20:05 +0300 From: "Michael S. Tsirkin" Message-ID: <20170829181921-mutt-send-email-mst@kernel.org> References: <20170829144805.28872-1-marcandre.lureau@redhat.com> <20170829144805.28872-2-marcandre.lureau@redhat.com> <20170829175820-mutt-send-email-mst@kernel.org> <20170829180900-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: Victor Kaplansky , QEMU On Tue, Aug 29, 2017 at 05:18:11PM +0200, Marc-Andr=E9 Lureau wrote: > Hi >=20 > On Tue, Aug 29, 2017 at 5:09 PM, Michael S. Tsirkin wr= ote: > > On Tue, Aug 29, 2017 at 05:04:34PM +0200, Marc-Andr=E9 Lureau wrote: > >> Hi > >> > >> On Tue, Aug 29, 2017 at 5:01 PM, Michael S. Tsirkin = wrote: > >> > On Tue, Aug 29, 2017 at 04:48:04PM +0200, Marc-Andr=E9 Lureau wrot= e: > >> >> This is the same workaround as commit 523b018dde3b765, which was = lost > >> >> with libvhost-user transition in commit e10e798c85c2331. > >> >> > >> >> Signed-off-by: Marc-Andr=E9 Lureau > >> >> --- > >> >> contrib/libvhost-user/libvhost-user.h | 5 +++++ > >> >> contrib/libvhost-user/libvhost-user.c | 13 +++++++++++++ > >> >> 2 files changed, 18 insertions(+) > >> >> > >> >> diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libv= host-user/libvhost-user.h > >> >> index 53ef222c0b..aca71717c1 100644 > >> >> --- a/contrib/libvhost-user/libvhost-user.h > >> >> +++ b/contrib/libvhost-user/libvhost-user.h > >> >> @@ -132,6 +132,7 @@ typedef void (*vu_set_features_cb) (VuDev *de= v, uint64_t features); > >> >> typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg= , > >> >> int *do_reply); > >> >> typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, b= ool started); > >> >> +typedef bool (*vu_queue_resume_to_used_cb) (VuDev *dev, int qidx= ); > >> >> > >> >> typedef struct VuDevIface { > >> >> /* called by VHOST_USER_GET_FEATURES to get the features bit= mask */ > >> >> @@ -148,6 +149,10 @@ typedef struct VuDevIface { > >> >> vu_process_msg_cb process_msg; > >> >> /* tells when queues can be processed */ > >> >> vu_queue_set_started_cb queue_set_started; > >> >> + /* If the queue must be resumed to vring.used->idx. */ > >> >> + /* This can help to support resuming on unmanaged exit/crash= when > >> >> + * the slave/driver processes elements in order. */ > >> >> + vu_queue_resume_to_used_cb queue_resume_to_used; > >> >> } VuDevIface; > >> >> > >> >> typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx); > >> > > >> > Let's consider: this is only safe if queue is processed in order. > >> > So I think that would be a better name for the field. > >> > > >> That's what the comment say already :) > >> > >> Which name do you suggest? vu_queue_is_processed_in_order? > > > > Something like this. > > > >> Does that > >> imply it should always resume? > > > > Not sure I understand the question. >=20 > If a "queue_is_processed_in_order", does that imply libvhost-user > should always resume it based on used_idx? I think it does, but the > correlation is less obvious than explicitly saying "resume_to_used". Just add a comment then. You do not want low level details like used index in all backends. >=20 > --=20 > Marc-Andr=E9 Lureau