Re: [Xen-devel] [PATCH 0/4] HVM Virtual S3

[Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>]

At 22:17 +0800 on 17 May (1179440232), Yu, Ke wrote:
> Ian Pratt  wrote on 2007??5??17?? 22:15:
> >> In VGA card side, the VESA FB emulation has not been tried yet, but
> >> the cirrus_vga works fine with Windows. Windows has cirrus VGA
> >> driver, which supports S3, So this issue is resolved.
> >> 
> >> Current issue is that Windows is not happy with the standard monitor
> >> driver. And unfortunately, seems there is no monitor emulation code
> >> in QEMU, so there may be no way to change the QEMU monitor type. It
> >> would be better if someone can tell how to change that.

Sorry for joining this thread quite late - I've been away for a few
weeks.

I found that the attached patch to the Cirrus VGA BIOS helps Windows
along (but not quite enough).  It adds some VBE power-management calls
to the BIOS, telling Windows that it's capable of putting the screen to
sleep.  Unfortunately, this just changes the error from the monitor
driver refusing to allow S3 to the Cirrus driver refusing to allow
it. :|

Tracing the BIOS and I/O activity of Windows, the next most likely
culprit is when the Cirrus driver tries to talk DDC2B to the monitor at
start of day (by frobbing the line state manually via Cirrus control
registers) and gets no response.  Since it can't read the monitor's
descriptor tables it can't be sure that it's possible to put it to sleep
properly.

Since implementing a DDC2B state machine and faking out the tables
sounds nasty, I agree with Ian that the VESA/VBE device model is
probably the way forward, in the hope of getting Windows to use BIOS
calls for all this.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

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