Re: [Xen-devel] libxl videoram for cirrus graphics

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2013-09-17 at 12:54 +0000, Rob Hoes wrote:
> Hi,
> 
> The videoram setting in xl config files is documented as follows:
> 
> "
> videoram=MBYTES
> 
>     Sets the amount of RAM which the emulated video card will contain,
> which in turn limits the resolutions and bit depths which will be
> available. The default amount of video ram for stdvga is 8MB which is
> sufficient for e.g. 1600x1200 at 32bpp and videoram option is
> currently working only when using the qemu-xen-traditional
> device-model.
> 
>     When using the emulated Cirrus graphics card (vga="cirrus") the
> amount of video ram is fixed at 4MB which is sufficient for 1024x768
> at 32 bpp and videoram option is currently working only when using the
> upstream qemu-xen device-model.
> "
> 
> XenServer also uses a default of 4MB video ram for cirrus graphics.
> 
> However, when I use xl to create a VM with cirrus graphics, I get 8MB
> of video RAM by default. Moreover, setting it to videoram=4 in the
> config file leads to complaints from libxl:
> 
>     libxl_create.c:228:libxl__domain_build_info_setdefault: videoram must be 
> at least 8 mb
> 
> Is there a bug in the logic in libxl_create.c?

Either the docs of the code or both would seem to be wrong. Since you
say you happily use 4MB in XenServer I guess it is both?

I noticed that the docs also say the amount is fixed, but that's not
what the code implements either..

I'm not really sure who, if anyone, might know definitively what is
going on here. Stefano has some involvement in this video mem stuff once
upon a time and Ian is the qemu-trad maintainer, so I've CCdthem
both ;-)

> 
> Cheers,
> Rob
> 
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> http://lists.xen.org/xen-devel



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