Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size

[Eric Blake <eblake@redhat.com>]

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On 05/09/2014 05:18 AM, Dr. David Alan Gilbert wrote:
> * arei.gonglei@huawei.com (arei.gonglei@huawei.com) wrote:
>> From: Gonglei <arei.gonglei@huawei.com>
>>
>> when configure a invalid vram size for cirrus card, such as less
>> 2 MB, which will crash qemu. Follow the real hardware, the cirrus
>> card has 4 MB video memory. Also for backward compatibility, accept
>> 8 MB and 16 MB vram size.
> 
> virt-manager/libvirt seems to default to 9 MByte of Vram for cirrus,
> so this would break a lot of setups.

I think it was virt-manager that made the mistake, but it is indeed a
historical wart that we are now stuck with (unless you argue that taking
the user's request and silently rounding up to the next power of 2 will
not be a guest-visible change).

> 
> Looking at datasheets on the web seems to say the chips actually went
> down to 1 MB or less.
> 
> I think before doing this change, it would be good to understand where
> the weird 9MB in libvirt/virt-manager came from, and what the limits of
> the emulator/drivers are.
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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