diff mbox series

[v4,2/4] vhost-vsock-pci: force virtio version 1

Message ID 20200921083807.48380-3-sgarzare@redhat.com
State Superseded
Headers show
Series vhost-vsock: force virtio version 1 | expand

Commit Message

Stefano Garzarella Sept. 21, 2020, 8:38 a.m. UTC
Commit 9b3a35ec82 ("virtio: verify that legacy support is not
accidentally on") added a safety check that requires to set
'disable-legacy=on' on vhost-vsock-pci device:

    $ ./qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=5
        qemu-system-x86_64: -device vhost-vsock-pci,guest-cid=5:
        device is modern-only, use disable-legacy=on

virtio-vsock was introduced after the release of VIRTIO 1.0
specifications, so it should be 'modern-only'.
In addition Cornelia verified that forcing a legacy mode on
vhost-vsock-pci device using x86-64 host and s390x guest, so with
different endianness, produces strange behaviours.

This patch forces virtio version 1 and removes the 'transitional_name'
property removing the need to specify 'disable-legacy=on' on
vhost-vsock-pci device.

To avoid migration issues, we force virtio version 1 only when
legacy check is enabled in the new machine types (>= 5.1).

Cc: qemu-stable@nongnu.org
Reported-by: Qian Cai <caiqian@redhat.com>
Reported-by: Qinghua Cheng <qcheng@redhat.com>
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1868449
Suggested-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
v3:
 - forced virtio version 1 only with new machine types
v2:
 - fixed commit message [Cornelia]
---
 hw/virtio/vhost-vsock-pci.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

Cornelia Huck Sept. 21, 2020, 9:46 a.m. UTC | #1
On Mon, 21 Sep 2020 10:38:05 +0200
Stefano Garzarella <sgarzare@redhat.com> wrote:

> Commit 9b3a35ec82 ("virtio: verify that legacy support is not

> accidentally on") added a safety check that requires to set

> 'disable-legacy=on' on vhost-vsock-pci device:

> 

>     $ ./qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=5

>         qemu-system-x86_64: -device vhost-vsock-pci,guest-cid=5:

>         device is modern-only, use disable-legacy=on

> 

> virtio-vsock was introduced after the release of VIRTIO 1.0

> specifications, so it should be 'modern-only'.

> In addition Cornelia verified that forcing a legacy mode on

> vhost-vsock-pci device using x86-64 host and s390x guest, so with

> different endianness, produces strange behaviours.

> 

> This patch forces virtio version 1 and removes the 'transitional_name'

> property removing the need to specify 'disable-legacy=on' on

> vhost-vsock-pci device.

> 

> To avoid migration issues, we force virtio version 1 only when

> legacy check is enabled in the new machine types (>= 5.1).


Maybe add

"As the transitional device name is not commonly used, we do not
provide compatibility handling for it." ?

> 

> Cc: qemu-stable@nongnu.org

> Reported-by: Qian Cai <caiqian@redhat.com>

> Reported-by: Qinghua Cheng <qcheng@redhat.com>

> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1868449

> Suggested-by: Cornelia Huck <cohuck@redhat.com>

> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

> ---

> v3:

>  - forced virtio version 1 only with new machine types

> v2:

>  - fixed commit message [Cornelia]

> ---

>  hw/virtio/vhost-vsock-pci.c | 10 +++++++++-

>  1 file changed, 9 insertions(+), 1 deletion(-)

> 


Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Stefano Garzarella Sept. 21, 2020, 9:57 a.m. UTC | #2
On Mon, Sep 21, 2020 at 11:46:02AM +0200, Cornelia Huck wrote:
> On Mon, 21 Sep 2020 10:38:05 +0200
> Stefano Garzarella <sgarzare@redhat.com> wrote:
> 
> > Commit 9b3a35ec82 ("virtio: verify that legacy support is not
> > accidentally on") added a safety check that requires to set
> > 'disable-legacy=on' on vhost-vsock-pci device:
> > 
> >     $ ./qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=5
> >         qemu-system-x86_64: -device vhost-vsock-pci,guest-cid=5:
> >         device is modern-only, use disable-legacy=on
> > 
> > virtio-vsock was introduced after the release of VIRTIO 1.0
> > specifications, so it should be 'modern-only'.
> > In addition Cornelia verified that forcing a legacy mode on
> > vhost-vsock-pci device using x86-64 host and s390x guest, so with
> > different endianness, produces strange behaviours.
> > 
> > This patch forces virtio version 1 and removes the 'transitional_name'
> > property removing the need to specify 'disable-legacy=on' on
> > vhost-vsock-pci device.
> > 
> > To avoid migration issues, we force virtio version 1 only when
> > legacy check is enabled in the new machine types (>= 5.1).
> 
> Maybe add
> 
> "As the transitional device name is not commonly used, we do not
> provide compatibility handling for it." ?

Yes, I'll add in v5.

> 
> > 
> > Cc: qemu-stable@nongnu.org
> > Reported-by: Qian Cai <caiqian@redhat.com>
> > Reported-by: Qinghua Cheng <qcheng@redhat.com>
> > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1868449
> > Suggested-by: Cornelia Huck <cohuck@redhat.com>
> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > ---
> > v3:
> >  - forced virtio version 1 only with new machine types
> > v2:
> >  - fixed commit message [Cornelia]
> > ---
> >  hw/virtio/vhost-vsock-pci.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> 
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Thanks,
Stefano
diff mbox series

Patch

diff --git a/hw/virtio/vhost-vsock-pci.c b/hw/virtio/vhost-vsock-pci.c
index e56067b427..205da8d1f5 100644
--- a/hw/virtio/vhost-vsock-pci.c
+++ b/hw/virtio/vhost-vsock-pci.c
@@ -44,6 +44,15 @@  static void vhost_vsock_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
 {
     VHostVSockPCI *dev = VHOST_VSOCK_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
+    VirtIODevice *virtio_dev = VIRTIO_DEVICE(vdev);
+
+    /*
+     * To avoid migration issues, we force virtio version 1 only when
+     * legacy check is enabled in the new machine types (>= 5.1).
+     */
+    if (!virtio_legacy_check_disabled(virtio_dev)) {
+        virtio_pci_force_virtio_1(vpci_dev);
+    }
 
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
 }
@@ -73,7 +82,6 @@  static void vhost_vsock_pci_instance_init(Object *obj)
 static const VirtioPCIDeviceTypeInfo vhost_vsock_pci_info = {
     .base_name             = TYPE_VHOST_VSOCK_PCI,
     .generic_name          = "vhost-vsock-pci",
-    .transitional_name     = "vhost-vsock-pci-transitional",
     .non_transitional_name = "vhost-vsock-pci-non-transitional",
     .instance_size = sizeof(VHostVSockPCI),
     .instance_init = vhost_vsock_pci_instance_init,