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Date: Tue, 23 Jul 2013 13:28:30 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH] vga: Start supporting resolution not
 multiple of 16 correctly.
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To: fantonifabio@tiscali.it
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Liguori <aliguori@us.ibm.com>, xen-devel@lists.xensource.com, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, qemu-devel <qemu-devel@nongnu.org>, Alon Levy <alevy@redhat.com>, Frediano Ziglio <freddy77@gmail.com>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>

  Hi,

> Tested-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
> 
> I tested it for a long time with spice on xen (because qxl will be fully
> working only after adding SSE support on hvm domUs). It works, I think
> it is good to add this and the respective vgabios patch on upstream.

>>          case VBE_DISPI_INDEX_XRES:
>> -            if ((val <= VBE_DISPI_MAX_XRES) && ((val & 7) == 0)) {
>> +            if ((val <= VBE_DISPI_MAX_XRES) && ((val & 1) == 0)) {
>>                  s->vbe_regs[s->vbe_index] = val;
>>              }
>>              break;

It's not that simple.  With 32bit depths common today it will work fine,
but for lower depths (especially those lower than 8bit) this will give
you broken scanline alignment.

cheers,
  Gerd