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Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size |
Date: |
Fri, 9 May 2014 13:02:25 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* Gerd Hoffmann (address@hidden) wrote:
> Hi,
>
> > virt-manager/libvirt seems to default to 9 MByte of Vram for cirrus,
> > so this would break a lot of setups.
>
> It wouldn't. libvirt sticks that into the xml, but it doesn't set any
> qemu parameters. The libvirt parameter actually predates the qemu
> property for setting the size.
Yeuch messy.
> > Looking at datasheets on the web seems to say the chips actually went
> > down to 1 MB or less.
>
> I have my doubts we emulate that correctly (register telling the guest
> how much memory is actually there etc.). Also it is pretty much useless
> these days, even the 4MB imply serious constrains when FullHD displays
> are commonplace. Newer cirrus drivers such as the kernel's drm driver
> are specifically written to qemu's cirrus cards, I have my doubs that
> they are prepared to handle 1MB cirrus cards correctly.
>
> Bottom line: Allowing less than 4MB is asking for trouble for no good
> reason ;)
OK, so checking for 4MB/8MB/16MB is probably safe, and it also would
have the benefit of shouting if someone fixed libvirt and it started
trying to configure a 9MB version.
Dave
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size, Dr. David Alan Gilbert, 2014/05/09
Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size, Paolo Bonzini, 2014/05/09
Re: [Qemu-devel] [PATCH] cirrus_vga: adding sanity check for vram size, Eric Blake, 2014/05/12