From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46181) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bPryV-0007Bl-Sw for qemu-devel@nongnu.org; Wed, 20 Jul 2016 09:55:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bPryQ-0002Kn-T3 for qemu-devel@nongnu.org; Wed, 20 Jul 2016 09:55:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36169) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bPryQ-0002K2-Gd for qemu-devel@nongnu.org; Wed, 20 Jul 2016 09:55:42 -0400 Date: Wed, 20 Jul 2016 16:55:34 +0300 From: "Michael S. Tsirkin" Message-ID: <20160720164529-mutt-send-email-mst@kernel.org> References: <20160706184721.2007-1-marcandre.lureau@redhat.com> <20160706184721.2007-11-marcandre.lureau@redhat.com> <20160720162900-mutt-send-email-mst@kernel.org> <583237603.6741968.1469022086004.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <583237603.6741968.1469022086004.JavaMail.zimbra@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 10/28] vhost: change some assert() for error_report() or silent fail List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: marcandre lureau , qemu-devel@nongnu.org, mukawa@igel.co.jp, yuanhan liu , victork@redhat.com, jonshin@cisco.com On Wed, Jul 20, 2016 at 09:41:26AM -0400, Marc-Andr=E9 Lureau wrote: >=20 >=20 > ----- Original Message ----- > > On Wed, Jul 06, 2016 at 08:47:03PM +0200, marcandre.lureau@redhat.com= wrote: > > > From: Marc-Andr=E9 Lureau > > >=20 > > > Calling a vhost operation may fail, especially with disconnectable > > > backends. Treat some that look harmless as recoverable errors (prin= t > > > error, or ignore on error code path). > > >=20 > > > Signed-off-by: Marc-Andr=E9 Lureau > >=20 > > These might be recoverable for vhost-user not for vhost_net. >=20 > I don't think we can hide all the error handling in vhost-user very > long, soon enough we will need to reset the guest device state. Interesting. This will need some thought. > If > vhost-net doesn't support error, it should rather assert() there, but > having the error handling done at higher level, at the vhost interface > level at least, not at the backend level.=20 Interesting. That might be reasonable too but would increase the scope of this already large patchset even further. > > IMO the backend should return 0 if error is benign, > > report errors to vhost only if they are fatal. >=20 > Imho whether it's fatal and how to recover as not much to do with the b= ackend (which each kind of just a proxy), it should be handled at higher = level, possibly up to the guest. Consider example below. EBADF means fd not writeable - remote exited so that's benign. EFAULT means code bug. vhost has no idea there's an fd though. > > For example, consider set mem table. Write failing is one thing, > > and it's benign, but e.g. table too big is another thing and isn't. > >=20 > > Also, we might want to distinguish between EBADF (fd closed) > > and other types of errors. All this knowledge belomgs in vhost user. > >=20 > > > --- > > > hw/virtio/vhost.c | 32 +++++++++++++++++++++----------- > > > 1 file changed, 21 insertions(+), 11 deletions(-) > > >=20 > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > > index 75bc51e..e03a031 100644 > > > --- a/hw/virtio/vhost.c > > > +++ b/hw/virtio/vhost.c > > > @@ -400,7 +400,10 @@ static inline void vhost_dev_log_resize(struct > > > vhost_dev *dev, uint64_t size) > > > /* inform backend of log switching, this must be done before > > > releasing the current log, to ensure no logging is lost */ > > > r =3D dev->vhost_ops->vhost_set_log_base(dev, log_base, log); > > > - assert(r >=3D 0); > > > + if (r < 0) { > > > + error_report("Failed to change backend log"); > > > + } > > > + > > > vhost_log_put(dev, true); > > > dev->log =3D log; > > > dev->log_size =3D size; > > > @@ -567,7 +570,9 @@ static void vhost_commit(MemoryListener *listen= er) > > > =20 > > > if (!dev->log_enabled) { > > > r =3D dev->vhost_ops->vhost_set_mem_table(dev, dev->mem); > > > - assert(r >=3D 0); > > > + if (r < 0) { > > > + error_report("Failed to set mem table"); > > > + } > > > dev->memory_changed =3D false; > > > return; > > > } > > > @@ -580,7 +585,9 @@ static void vhost_commit(MemoryListener *listen= er) > > > vhost_dev_log_resize(dev, log_size + VHOST_LOG_BUFFER); > > > } > > > r =3D dev->vhost_ops->vhost_set_mem_table(dev, dev->mem); > > > - assert(r >=3D 0); > > > + if (r < 0) { > > > + error_report("Failed to set mem table"); > > > + } > > > /* To log less, can only decrease log size after table update.= */ > > > if (dev->log_size > log_size + VHOST_LOG_BUFFER) { > > > vhost_dev_log_resize(dev, log_size); > > > @@ -649,6 +656,7 @@ static int vhost_virtqueue_set_addr(struct vhos= t_dev > > > *dev, > > > }; > > > int r =3D dev->vhost_ops->vhost_set_vring_addr(dev, &addr); > > > if (r < 0) { > > > + error_report("Failed to set vring addr"); > > > return -errno; > > > } > > > return 0; > > > @@ -662,12 +670,15 @@ static int vhost_dev_set_features(struct vhos= t_dev > > > *dev, bool enable_log) > > > features |=3D 0x1ULL << VHOST_F_LOG_ALL; > > > } > > > r =3D dev->vhost_ops->vhost_set_features(dev, features); > > > + if (r < 0) { > > > + error_report("Failed to set features"); > > > + } > > > return r < 0 ? -errno : 0; > > > } > > > =20 > > > static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_lo= g) > > > { > > > - int r, t, i, idx; > > > + int r, i, idx; > > > r =3D vhost_dev_set_features(dev, enable_log); > > > if (r < 0) { > > > goto err_features; > > > @@ -684,12 +695,10 @@ static int vhost_dev_set_log(struct vhost_dev= *dev, > > > bool enable_log) > > > err_vq: > > > for (; i >=3D 0; --i) { > > > idx =3D dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_in= dex + i); > > > - t =3D vhost_virtqueue_set_addr(dev, dev->vqs + i, idx, > > > - dev->log_enabled); > > > - assert(t >=3D 0); > > > + vhost_virtqueue_set_addr(dev, dev->vqs + i, idx, > > > + dev->log_enabled); > > > } > > > - t =3D vhost_dev_set_features(dev, dev->log_enabled); > > > - assert(t >=3D 0); > > > + vhost_dev_set_features(dev, dev->log_enabled); > > > err_features: > > > return r; > > > } > > > @@ -937,7 +946,6 @@ static void vhost_virtqueue_stop(struct vhost_d= ev *dev, > > > } > > > } > > > =20 > > > - assert (r >=3D 0); > > > cpu_physical_memory_unmap(vq->ring, virtio_queue_get_ring_size= (vdev, > > > idx), > > > 0, virtio_queue_get_ring_size(vdev, = idx)); > > > cpu_physical_memory_unmap(vq->used, virtio_queue_get_used_size= (vdev, > > > idx), > > > @@ -1191,7 +1199,9 @@ void vhost_virtqueue_mask(struct vhost_dev *h= dev, > > > VirtIODevice *vdev, int n, > > > =20 > > > file.index =3D hdev->vhost_ops->vhost_get_vq_index(hdev, n); > > > r =3D hdev->vhost_ops->vhost_set_vring_call(hdev, &file); > > > - assert(r >=3D 0); > > > + if (r < 0) { > > > + error_report("Failed to set vring call"); > > > + } > > > } > > > =20 > > > uint64_t vhost_get_features(struct vhost_dev *hdev, const int > > > *feature_bits, > > > -- > > > 2.9.0 > >=20