On Mon, Dec 23, 2019 at 12:02:18PM +0100, Paolo Bonzini wrote:
> On 23/12/19 10:18, Yang Zhong wrote:
> > In this time, the queue number in the front-end block driver is 2, but
> > the queue number in qemu side is still 4. So the guest virtio_blk
> > driver will failed to create vq with backend.
>
> Where?
>
> > There is no "set back"
> > mechnism for block driver to inform backend this new queue number.
> > So, i added this check in qemu side.
>
> Perhaps the guest kernel should still create the virtqueues, and just
> not use them. In any case, now that you have explained it, it is
> certainly a guest bug.
>
> Paolo
Paolo do you understand where the bug is?
E.g. I see this in vhost user block:
/* Kick right away to begin processing requests already in vring */
for (i = 0; i < s->dev.nvqs; i++) {
VirtQueue *kick_vq = virtio_get_queue(vdev, i);
if (!virtio_queue_get_desc_addr(vdev, i)) {
continue;
}
event_notifier_set(virtio_queue_get_host_notifier(kick_vq));
}
which is an (admittedly hacky) want to skip VQs which
were not configured by guest ....
> > Since the current virtio-blk and vhost-user-blk device always
> > defaultly use 1 queue, it's hard to find this issue.
> >
> > I checked the guest kernel driver, virtio-scsi and virtio-blk all
> > have same check in their driver probe:
> >
> > num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
> >
> > It's possible the guest driver has different queue number with qemu
> > side.
> >
> > I also want to fix this issue from guest driver side, but currently there
> > is no better solution to fix this issue.
> >
> > By the way, i did not try scsi with this corner case, and only check
> > driver and qemu code to find same issue. thanks!
> >
> > Yang
> >
> >> Paolo
> >>
> >>> Signed-off-by: Yang Zhong <yang.zh...@intel.com>
> >>> ---
> >>> hw/block/vhost-user-blk.c | 11 +++++++++++
> >>> hw/block/virtio-blk.c | 11 ++++++++++-
> >>> hw/scsi/virtio-scsi.c | 12 ++++++++++++
> >>> 3 files changed, 33 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> >>> index 63da9bb619..250e72abe4 100644
> >>> --- a/hw/block/vhost-user-blk.c
> >>> +++ b/hw/block/vhost-user-blk.c
> >>> @@ -23,6 +23,8 @@
> >>> #include "qom/object.h"
> >>> #include "hw/qdev-core.h"
> >>> #include "hw/qdev-properties.h"
> >>> +#include "qemu/option.h"
> >>> +#include "qemu/config-file.h"
> >>> #include "hw/virtio/vhost.h"
> >>> #include "hw/virtio/vhost-user-blk.h"
> >>> #include "hw/virtio/virtio.h"
> >>> @@ -391,6 +393,7 @@ static void vhost_user_blk_device_realize(DeviceState
> >>> *dev, Error **errp)
> >>> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> >>> VHostUserBlk *s = VHOST_USER_BLK(vdev);
> >>> Error *err = NULL;
> >>> + unsigned cpus;
> >>> int i, ret;
> >>>
> >>> if (!s->chardev.chr) {
> >>> @@ -403,6 +406,14 @@ static void
> >>> vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
> >>> return;
> >>> }
> >>>
> >>> + cpus =
> >>> qemu_opt_get_number(qemu_opts_find(qemu_find_opts("smp-opts"), NULL),
> >>> + "cpus", 0);
> >>> + if (s->num_queues > cpus ) {
> >>> + error_setg(errp, "vhost-user-blk: the queue number should be
> >>> equal "
> >>> + "or less than vcpu number");
> >>> + return;
> >>> + }
> >>> +
> >>> if (!s->queue_size) {
> >>> error_setg(errp, "vhost-user-blk: queue size must be non-zero");
> >>> return;
> >>> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> >>> index d62e6377c2..b2f4d01148 100644
> >>> --- a/hw/block/virtio-blk.c
> >>> +++ b/hw/block/virtio-blk.c
> >>> @@ -18,6 +18,8 @@
> >>> #include "qemu/error-report.h"
> >>> #include "qemu/main-loop.h"
> >>> #include "trace.h"
> >>> +#include "qemu/option.h"
> >>> +#include "qemu/config-file.h"
> >>> #include "hw/block/block.h"
> >>> #include "hw/qdev-properties.h"
> >>> #include "sysemu/blockdev.h"
> >>> @@ -1119,7 +1121,7 @@ static void virtio_blk_device_realize(DeviceState
> >>> *dev, Error **errp)
> >>> VirtIOBlock *s = VIRTIO_BLK(dev);
> >>> VirtIOBlkConf *conf = &s->conf;
> >>> Error *err = NULL;
> >>> - unsigned i;
> >>> + unsigned i,cpus;
> >>>
> >>> if (!conf->conf.blk) {
> >>> error_setg(errp, "drive property not set");
> >>> @@ -1133,6 +1135,13 @@ static void virtio_blk_device_realize(DeviceState
> >>> *dev, Error **errp)
> >>> error_setg(errp, "num-queues property must be larger than 0");
> >>> return;
> >>> }
> >>> + cpus =
> >>> qemu_opt_get_number(qemu_opts_find(qemu_find_opts("smp-opts"), NULL),
> >>> + "cpus", 0);
> >>> + if (conf->num_queues > cpus ) {
> >>> + error_setg(errp, "virtio-blk: the queue number should be equal "
> >>> + "or less than vcpu number");
> >>> + return;
> >>> + }
> >>> if (!is_power_of_2(conf->queue_size) ||
> >>> conf->queue_size > VIRTQUEUE_MAX_SIZE) {
> >>> error_setg(errp, "invalid queue-size property (%" PRIu16 "), "
> >>> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> >>> index e8b2b64d09..8e3e44f6b9 100644
> >>> --- a/hw/scsi/virtio-scsi.c
> >>> +++ b/hw/scsi/virtio-scsi.c
> >>> @@ -21,6 +21,8 @@
> >>> #include "qemu/error-report.h"
> >>> #include "qemu/iov.h"
> >>> #include "qemu/module.h"
> >>> +#include "qemu/option.h"
> >>> +#include "qemu/config-file.h"
> >>> #include "sysemu/block-backend.h"
> >>> #include "hw/qdev-properties.h"
> >>> #include "hw/scsi/scsi.h"
> >>> @@ -880,6 +882,7 @@ void virtio_scsi_common_realize(DeviceState *dev,
> >>> {
> >>> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> >>> VirtIOSCSICommon *s = VIRTIO_SCSI_COMMON(dev);
> >>> + unsigned cpus;
> >>> int i;
> >>>
> >>> virtio_init(vdev, "virtio-scsi", VIRTIO_ID_SCSI,
> >>> @@ -893,6 +896,15 @@ void virtio_scsi_common_realize(DeviceState *dev,
> >>> virtio_cleanup(vdev);
> >>> return;
> >>> }
> >>> +
> >>> + cpus =
> >>> qemu_opt_get_number(qemu_opts_find(qemu_find_opts("smp-opts"), NULL),
> >>> + "cpus", 0);
> >>> + if (s->conf.num_queues > cpus ) {
> >>> + error_setg(errp, "virtio-scsi: the queue number should be equal "
> >>> + "or less than vcpu number");
> >>> + return;
> >>> + }
> >>> +
> >>> s->cmd_vqs = g_new0(VirtQueue *, s->conf.num_queues);
> >>> s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE;
> >>> s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE;
> >>>
> >
