Re: [Qemu-devel] [PATCH v3] tools/libxl: Improve videoram setting

[Fabio Fantoni]

Il 14/01/2013 19:21, Stefano Stabellini ha scritto:
> I did a quick test and it seems that it should be possible to change 
> the amount of videoram for stdvga too using the same command line 
> option, however at the moment it just errors out. Therefore I am OK 
> with this patch only taking care of Cirrus for the moment. 
I found details about stdvga on qemu upstream:
http://xenbits.xen.org/gitweb/?p=staging/qemu-upstream-unstable.git;a=blob_plain;f=docs/specs/standard-vga.txt;hb=HEAD

It seems that stdvga memory by default is 16 mb, while xen reserves only 
8 mb by default and doen't logs any error.
For cirrus, increasing memory seems to be correct and without error with 
my patch.
WIth both cirrus and stdvga under qemu upstream with xen the performance 
are really poor even if I increase video memory, respect to qemu-only 
and qemu-kvm (without xen).
Qxl is definitely not working under xen and conversely is ok on qemu-kvm 
and qemu-only.

It seem that xen need change and/or fix to have full working emulated 
vga on qemu upstream.
At the moment all emulated vgas have problems with xen that aren't 
present without xen.

The performance differences are noticeable (in some case very big) with 
xen and without xen using resolution > 1024x768.

Probably the first link explain the change/fix necessary in xen about 
vga (probably in hvmloader).
I tried to do that more times failing but unfortunately I do not have 
sufficient knowledge about this.
Can someone help me please?

I think this is important, years ago the minimal resolution used on 
desktop was 1024x768, and no problem with actual vga setting but now 
minimal resolution seems increased to up 1366x768 and many people are 
using even higher resolutions.
http://www.screenresolution.org/year-2013/

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