Re: [Qemu-devel] [PATCH] compat: Use explicit type names on HW_COMPAT_2_6

[Michael S. Tsirkin]

On Fri, Jan 04, 2019 at 01:22:26AM -0200, Eduardo Habkost wrote:
> The virtio-pci entries in HW_COMPAT_2_6 had an implicit
> assumption: that all virtio-pci subclasses support the
> disable-legacy and disable-modern options.
> 
> That assumption was broken by commit f6e501a28ef9 ("virtio:
> Provide version-specific variants of virtio PCI devices").  This
> caused QEMU to crash if using the new -non-transitional or
> -transitional device types:
> 
>   $ qemu-system-x86_64 -machine pc-i440fx-2.6 \
>     -device virtio-net-pci-non-transitional
>   Unexpected error in object_property_find() at qom/object.c:1092:
>   qemu-system-x86_64: -device virtio-net-pci-non-transitional: can't apply \
>   global virtio-pci.disable-modern=on: Property '.disable-modern' not found
>   Aborted (core dumped)
> 
> Replace the virtio-pci.disable-legacy=off and
> virtio-pci.disable-modern=on entries on HW_COMPAT_2_6 with
> explicit entries for each generic virtio device type.
> 
> The full list of generic virtio device types was extracted by
> just grepping for ".generic_name".  Note that we don't need to
> worry about listing new virtio-pci devices in HW_COMPAT_2_6 in
> the future, because new devices won't require QEMU 2.6
> compatibility.

I fully expect that e.g. packed ring support will need
to affect all virtio devices too. And it's likely
that we'll have some new virtio-pci transport features too.

> This makes the compat entries annoyingly verbose, but is simpler
> than the alternative of making the virtio-pci type inheritance
> rules even more complex.

God forbid we forgot something, the only way to notice is to
run a cross version migration with an old qemu.
I think we need to come up with something less verbose and fragile.


> Reported-by: Thomas Huth <address@hidden>
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
> ---
>  include/hw/compat.h | 140 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 138 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/compat.h b/include/hw/compat.h
> index 3ca85b037c..fbb6c1138a 100644
> --- a/include/hw/compat.h
> +++ b/include/hw/compat.h
> @@ -163,11 +163,147 @@
>          .property = "format_transport_address",\
>          .value    = "off",\
>      },{\
> -        .driver   = "virtio-pci",\
> +        .driver   = "vhost-scsi-pci",\
>          .property = "disable-modern",\
>          .value    = "on",\
>      },{\
> -        .driver   = "virtio-pci",\
> +        .driver   = "vhost-scsi-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "vhost-user-blk-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "vhost-user-blk-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "vhost-user-scsi-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "vhost-user-scsi-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "vhost-vsock-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "vhost-vsock-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-9p-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-9p-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-balloon-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-balloon-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-blk-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-blk-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-crypto-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-crypto-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-gpu-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-gpu-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-input-host-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-input-host-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-keyboard-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-keyboard-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-mouse-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-mouse-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-net-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-net-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-rng-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-rng-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-scsi-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-scsi-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-serial-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-serial-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-tablet-pci",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-tablet-pci",\
> +        .property = "disable-legacy",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "virtio-vga",\
> +        .property = "disable-modern",\
> +        .value    = "on",\
> +    },{\
> +        .driver   = "virtio-vga",\
>          .property = "disable-legacy",\
>          .value    = "off",\
>      },
> -- 
> 2.18.0.rc1.1.g3f1ff2140