From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39760) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dmi4J-0005NK-Hc for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:04:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dmi4D-0008GD-NQ for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:04:43 -0400 Received: from mail-ua0-x243.google.com ([2607:f8b0:400c:c08::243]:38190) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dmi4D-0008FX-IQ for qemu-devel@nongnu.org; Tue, 29 Aug 2017 11:04:37 -0400 Received: by mail-ua0-x243.google.com with SMTP id j46so1528885uag.5 for ; Tue, 29 Aug 2017 08:04:36 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170829175820-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> From: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= Date: Tue, 29 Aug 2017 17:04:34 +0200 Message-ID: Content-Type: text/plain; charset="UTF-8" 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: "Michael S. Tsirkin" Cc: Victor Kaplansky , QEMU 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=C3=A9 Lureau wrote: >> This is the same workaround as commit 523b018dde3b765, which was lost >> with libvhost-user transition in commit e10e798c85c2331. >> >> Signed-off-by: Marc-Andr=C3=A9 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/libvhost-us= er/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 *dev, uint= 64_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, bool sta= rted); >> +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 bitmask */ >> @@ -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? Does that imply it should always resume? > >> diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-us= er/libvhost-user.c >> index 35fa0c5e56..36439caed6 100644 >> --- a/contrib/libvhost-user/libvhost-user.c >> +++ b/contrib/libvhost-user/libvhost-user.c >> @@ -521,6 +521,19 @@ vu_set_vring_addr_exec(VuDev *dev, VhostUserMsg *vm= sg) >> >> vq->used_idx =3D vq->vring.used->idx; >> >> + if (vq->last_avail_idx !=3D vq->used_idx) { >> + bool resume =3D dev->iface->queue_resume_to_used && >> + dev->iface->queue_resume_to_used(dev, index); >> + >> + DPRINT("Last avail index !=3D used index: %u !=3D %u%s\n", >> + vq->last_avail_idx, vq->used_idx, >> + resume ? ", resuming" : ""); >> + >> + if (resume) { >> + vq->shadow_avail_idx =3D vq->last_avail_idx =3D vq->used_id= x; >> + } >> + } >> + >> return false; >> } >> >> -- >> 2.14.1.146.gd35faa819 > --=20 Marc-Andr=C3=A9 Lureau