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Re: [Xen-devel] [Qemu-devel] [v2][PATCH 4/8] xen, gfx passthrough: reserve 00:02.0 for INTEL IGD

On 06/24/14 22:49, Chen, Tiejun wrote:
> On 2014/5/19 19:22, Gerd Hoffmann wrote:
>>   Hi,
>>> I think '-vga none' just guarantees the qemu vga cards doesn't occupy
>>> 00:02.0, but this doesn't mean others use this specific slot since in
>>> qemu internal, we always pass -1 to assign a slot automatically to
>>> register a PCI device. So in some cases, we can't get this slot as we
>>> expect since that is already assigned previously before we need this.
>> Yes, -vga, -net nic, -drive if=scsi (maybe more) can internally create
>> pci devices with auto slot assignment, which will occupy slot 2 indeed.
>> Use -device instead to create the devices.
>>> PCI: slot 2 function 0 not available for xen-pci-passthrough, in use
>>> by xen-platform
>> Ah, the xen platform device.  /me looks.  Ah, pc_xen_hvm_init creates
>> this automatically.  Two options here IMHO:
>>   (1) Just move it somewhere else explicitly.  For example slot 3, or
>>       make it a southbridge function (say 00:01.7).
>>   (2) Don't create it automatically, instead expect management add it
>>       if needed, using -device xen-plaform,addr=...
> Gerd,
> Sorry I return this discussion again.
> As we discussed here, we should never use -vga xxx to avoid occupying 
> slot 2. Instead, we will just use -device to create that emulated vga 
> device as you said like this:
> -device VGA,vgamem_mb=8,addr=0x4
> But looks this may issue another problem. That is we can't see 
> anything until the vga driver is initialized. I means if we pass 
> `-device VGA,vgamem_mb=8,addr=0x4', qemu doesn't expose any vga 
> interface to BIOS. Right? Or I'm still missing something.

I know for Xen that


also needs to change:

             /* Make cirrues VGA S3 suspend/resume work in Windows 
XP/2003 */
             Device (VGA)
-               Name (_ADR, 0x00020000)
+               // Address of the VGA (device F function 0)
+               Name (_ADR, 0x000F0000)

is what I have for:

-device VGA,vgamem_mb=8,addr=0xF.0x0

I am not sure, but think that QEMU without Xen does this acpi
adjustment at run time.

I also change seabios's config to include more VGA support but
not sure it is needed.

     -Don Slutz

> Thanks
> Tiejun
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