Re: [PATCH] hw/core/machine: move compatibility flags for VirtIO-net USO to machine 8.1

[Peter Xu <peterx@redhat.com>]

On Fri, May 17, 2024 at 09:53:36AM +0200, Fiona Ebner wrote:
> Migration from an 8.2 or 9.0 binary to an 8.1 binary with machine
> version 8.1 can fail with:
> 
> > kvm: Features 0x1c0010130afffa7 unsupported. Allowed features: 0x10179bfffe7
> > kvm: Failed to load virtio-net:virtio
> > kvm: error while loading state for instance 0x0 of device '0000:00:12.0/virtio-net'
> > kvm: load of migration failed: Operation not permitted
> 
> The series
> 
> 53da8b5a99 virtio-net: Add support for USO features
> 9da1684954 virtio-net: Add USO flags to vhost support.
> f03e0cf63b tap: Add check for USO features
> 2ab0ec3121 tap: Add USO support to tap device.
> 
> only landed in QEMU 8.2, so the compatibility flags should be part of
> machine version 8.1.
> 
> Moving the flags unfortunately breaks forward migration with machine
> version 8.1 from a binary without this patch to a binary with this
> patch.
> 

I think it'll be nicer we always copy stable in the commit log, so that
"whether to copy stable" is stick with the patch:

Cc: qemu-stable <qemu-stable@nongnu.org>

Even though it's not required for qemu stable process (I'd say that's
because we have a good stable tree maintainer..).

So we need this in qemu 8.1, 8.2 and 9.0?

> Fixes: 53da8b5a99 ("virtio-net: Add support for USO features")
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

> ---
>  hw/core/machine.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index c7ceb11501..95051b80db 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -50,15 +50,15 @@ GlobalProperty hw_compat_8_1[] = {
>      { "ramfb", "x-migrate", "off" },
>      { "vfio-pci-nohotplug", "x-ramfb-migrate", "off" },
>      { "igb", "x-pcie-flr-init", "off" },
> +    { TYPE_VIRTIO_NET, "host_uso", "off"},
> +    { TYPE_VIRTIO_NET, "guest_uso4", "off"},
> +    { TYPE_VIRTIO_NET, "guest_uso6", "off"},
>  };
>  const size_t hw_compat_8_1_len = G_N_ELEMENTS(hw_compat_8_1);
>  
>  GlobalProperty hw_compat_8_0[] = {
>      { "migration", "multifd-flush-after-each-section", "on"},
>      { TYPE_PCI_DEVICE, "x-pcie-ari-nextfn-1", "on" },
> -    { TYPE_VIRTIO_NET, "host_uso", "off"},
> -    { TYPE_VIRTIO_NET, "guest_uso4", "off"},
> -    { TYPE_VIRTIO_NET, "guest_uso6", "off"},
>  };
>  const size_t hw_compat_8_0_len = G_N_ELEMENTS(hw_compat_8_0);
>  
> -- 
> 2.39.2
> 
> 
> 

-- 
Peter Xu