[libvirt] [PATCH] qemu: Reject SDL graphic if it's not supported by qemu

[Eric Blake]

On 01/11/2011 04:29 AM, Daniel P. Berrange wrote:
> On Tue, Jan 11, 2011 at 03:43:07PM +0800, Osier Yang wrote:
>> If the emulator doesn't support SDL graphic, we should reject
>> the use of SDL graphic xml with error messages, but not ignore
>> it silently.
>>
>> * src/qemu/qemu_command.c
> 
> NACK.
> 
> Most previous versions of QEMU don't have any explicit -sdl
> flag. You got SDL automagically when *no* -vnc flag was
> given. So this change breaks many old QEMU versions.

We should know (or be able to find out) the precise version of qemu
where sdl was added as an explicit device.  Once we do that, it's easy
enough to modify libvirt's qemu/qemu_capabilities.h to add yet another
flag bit, and qemu_capabilities.c to set that flag bit to true for old
versions where SDL is automatic, and to new versions where SDL is
explicitly available, while leaving it false on new versions (such as
the RHEL build) where SDL is disabled.

I agree that it doesn't scale well for other features with similar
treatments, but the entire qemu_capabilities.c file is an example of the
effect of poor scalability of upstream qemu.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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