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Re: [Qemu-devel] [PATCH v3 10/28] vhost: change some assert() for error_
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH v3 10/28] vhost: change some assert() for error_report() or silent fail |
Date: |
Wed, 20 Jul 2016 09:41:26 -0400 (EDT) |
----- Original Message -----
> On Wed, Jul 06, 2016 at 08:47:03PM +0200, address@hidden wrote:
> > From: Marc-André Lureau <address@hidden>
> >
> > Calling a vhost operation may fail, especially with disconnectable
> > backends. Treat some that look harmless as recoverable errors (print
> > error, or ignore on error code path).
> >
> > Signed-off-by: Marc-André Lureau <address@hidden>
>
> These might be recoverable for vhost-user not for vhost_net.
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. 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.
> IMO the backend should return 0 if error is benign,
> report errors to vhost only if they are fatal.
Imho whether it's fatal and how to recover as not much to do with the backend
(which each kind of just a proxy), it should be handled at higher level,
possibly up to the guest.
> 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.
>
> Also, we might want to distinguish between EBADF (fd closed)
> and other types of errors. All this knowledge belomgs in vhost user.
>
> > ---
> > hw/virtio/vhost.c | 32 +++++++++++++++++++++-----------
> > 1 file changed, 21 insertions(+), 11 deletions(-)
> >
> > 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 = dev->vhost_ops->vhost_set_log_base(dev, log_base, log);
> > - assert(r >= 0);
> > + if (r < 0) {
> > + error_report("Failed to change backend log");
> > + }
> > +
> > vhost_log_put(dev, true);
> > dev->log = log;
> > dev->log_size = size;
> > @@ -567,7 +570,9 @@ static void vhost_commit(MemoryListener *listener)
> >
> > if (!dev->log_enabled) {
> > r = dev->vhost_ops->vhost_set_mem_table(dev, dev->mem);
> > - assert(r >= 0);
> > + if (r < 0) {
> > + error_report("Failed to set mem table");
> > + }
> > dev->memory_changed = false;
> > return;
> > }
> > @@ -580,7 +585,9 @@ static void vhost_commit(MemoryListener *listener)
> > vhost_dev_log_resize(dev, log_size + VHOST_LOG_BUFFER);
> > }
> > r = dev->vhost_ops->vhost_set_mem_table(dev, dev->mem);
> > - assert(r >= 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 vhost_dev
> > *dev,
> > };
> > int r = 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 vhost_dev
> > *dev, bool enable_log)
> > features |= 0x1ULL << VHOST_F_LOG_ALL;
> > }
> > r = dev->vhost_ops->vhost_set_features(dev, features);
> > + if (r < 0) {
> > + error_report("Failed to set features");
> > + }
> > return r < 0 ? -errno : 0;
> > }
> >
> > static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
> > {
> > - int r, t, i, idx;
> > + int r, i, idx;
> > r = 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 >= 0; --i) {
> > idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
> > - t = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
> > - dev->log_enabled);
> > - assert(t >= 0);
> > + vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
> > + dev->log_enabled);
> > }
> > - t = vhost_dev_set_features(dev, dev->log_enabled);
> > - assert(t >= 0);
> > + vhost_dev_set_features(dev, dev->log_enabled);
> > err_features:
> > return r;
> > }
> > @@ -937,7 +946,6 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
> > }
> > }
> >
> > - assert (r >= 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 *hdev,
> > VirtIODevice *vdev, int n,
> >
> > file.index = hdev->vhost_ops->vhost_get_vq_index(hdev, n);
> > r = hdev->vhost_ops->vhost_set_vring_call(hdev, &file);
> > - assert(r >= 0);
> > + if (r < 0) {
> > + error_report("Failed to set vring call");
> > + }
> > }
> >
> > uint64_t vhost_get_features(struct vhost_dev *hdev, const int
> > *feature_bits,
> > --
> > 2.9.0
>
- [Qemu-devel] [PATCH v3 03/28] vhost: don't assume opaque is a fd, use backend cleanup, (continued)
- [Qemu-devel] [PATCH v3 03/28] vhost: don't assume opaque is a fd, use backend cleanup, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 04/28] vhost: make vhost_log_put() idempotent, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 06/28] vhost: add vhost device only after all success, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 07/28] vhost: make vhost_dev_cleanup() idempotent, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 08/28] vhost-net: always call vhost_dev_cleanup() on failure, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 09/28] vhost: fix calling vhost_dev_cleanup() after vhost_dev_init(), marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 05/28] vhost: call vhost_log_put() on cleanup, marcandre . lureau, 2016/07/06
- [Qemu-devel] [PATCH v3 10/28] vhost: change some assert() for error_report() or silent fail, marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 11/28] vhost: use error_report() instead of fprintf(stderr, ...), marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 12/28] vhost-user: check qemu_chr_fe_set_msgfds() return value, marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 13/28] vhost-user: check vhost_user_{read, write}() return value, marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 14/28] qemu-char: check socket is actually connected, marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 15/28] vhost-user: keep vhost_net after a disconnection, marcandre . lureau, 2016/07/06
[Qemu-devel] [PATCH v3 16/28] Revert "vhost-net: do not crash if backend is not present", marcandre . lureau, 2016/07/06