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virtio: skip legacy support check on machine types less than 5.1 

Commit 9b3a35ec82 ("virtio: verify that legacy support is not accidentally
on") added a check that returns an error if legacy support is on, but the
device does not support legacy.

Unfortunately some devices were wrongly declared legacy capable even if
they were not (e.g vhost-vsock).

To avoid migration issues, we add a virtio-device property
(x-disable-legacy-check) to skip the legacy error, printing a warning
instead, for machine types < 5.1.

Cc: qemu-stable@nongnu.org
Fixes: 9b3a35ec82 ("virtio: verify that legacy support is not accidentally on")
Suggested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Suggested-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20200921122506.82515-2-sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
master
Stefano Garzarella 2020-09-21 14:25:03 +02:00 committed by Michael S. Tsirkin
parent 40bc0ca924
commit d55f518248
5 changed files with 34 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
hw/core/machine.c
View File

@ -44,6 +44,7 @@ GlobalProperty hw_compat_5_0[] = {
{ "vmport", "x-signal-unsupported-cmd", "off" },
{ "vmport", "x-report-vmx-type", "off" },
{ "vmport", "x-cmds-v2", "off" },
{ "virtio-device", "x-disable-legacy-check", "true" },
};
const size_t hw_compat_5_0_len = G_N_ELEMENTS(hw_compat_5_0);

15
hw/s390x/virtio-ccw.c
View File

@ -1122,9 +1122,18 @@ static void virtio_ccw_device_plugged(DeviceState *d, Error **errp)
}
if (!virtio_ccw_rev_max(dev) && !virtio_legacy_allowed(vdev)) {
error_setg(errp, "Invalid value of property max_rev "
"(is %d expected >= 1)", virtio_ccw_rev_max(dev));
return;
/*
* To avoid migration issues, we allow legacy mode when legacy
* check is disabled in the old machine types (< 5.1).
*/
if (virtio_legacy_check_disabled(vdev)) {
warn_report("device requires revision >= 1, but for backward "
"compatibility max_revision=0 is allowed");
} else {
error_setg(errp, "Invalid value of property max_rev "
"(is %d expected >= 1)", virtio_ccw_rev_max(dev));
return;
}
}
if (virtio_get_num_queues(vdev) > VIRTIO_QUEUE_MAX) {

14
hw/virtio/virtio-pci.c
View File

@ -1597,8 +1597,18 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
if (legacy) {
if (!virtio_legacy_allowed(vdev)) {
error_setg(errp, "device is modern-only, use disable-legacy=on");
return;
/*
* To avoid migration issues, we allow legacy mode when legacy
* check is disabled in the old machine types (< 5.1).
*/
if (virtio_legacy_check_disabled(vdev)) {
warn_report("device is modern-only, but for backward "
"compatibility legacy is allowed");
} else {
error_setg(errp,
"device is modern-only, use disable-legacy=on");
return;
}
}
if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
error_setg(errp, "VIRTIO_F_IOMMU_PLATFORM was supported by"

7
hw/virtio/virtio.c
View File

@ -3304,6 +3304,11 @@ bool virtio_legacy_allowed(VirtIODevice *vdev)
}
}
bool virtio_legacy_check_disabled(VirtIODevice *vdev)
{
return vdev->disable_legacy_check;
}
hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
{
return vdev->vq[n].vring.desc;
@ -3713,6 +3718,8 @@ static Property virtio_properties[] = {
DEFINE_VIRTIO_COMMON_FEATURES(VirtIODevice, host_features),
DEFINE_PROP_BOOL("use-started", VirtIODevice, use_started, true),
DEFINE_PROP_BOOL("use-disabled-flag", VirtIODevice, use_disabled_flag, true),
DEFINE_PROP_BOOL("x-disable-legacy-check", VirtIODevice,
disable_legacy_check, false),
DEFINE_PROP_END_OF_LIST(),
};

2
include/hw/virtio/virtio.h
View File

@ -101,6 +101,7 @@ struct VirtIODevice
bool use_started;
bool started;
bool start_on_kick; /* when virtio 1.0 feature has not been negotiated */
bool disable_legacy_check;
VMChangeStateEntry *vmstate;
char *bus_name;
uint8_t device_endian;
@ -394,5 +395,6 @@ static inline bool virtio_device_disabled(VirtIODevice *vdev)
}
bool virtio_legacy_allowed(VirtIODevice *vdev);
bool virtio_legacy_check_disabled(VirtIODevice *vdev);
#endif