Xen devel - Oct 2013 - setup_vga_pt seems can not correctly use vgabios.

hi, 

In xen-4.3.0/tools/qemu-xen-traditional/hw/pt-graphics.c,  setup_vga_pt calls
get_vgabios to get vgabios of passed-through VGA adapter, but get_vgabios only
read bios from /dev/mem,  /dev/mem is domain 0’s memory device. /dev/mem should
only contain the vgabios of primary VGA adapter of domain 0.

So if I want to pass through secondary adapter of domain 0 to domain U.
setup_vga_pt cannot correctly setup VGABIOS for domain U. Is this correct? Any
comments are appreciated.

thanks
huiming



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On Monday, October 28, 2013 3:24 PM Huiming wrote;
>hi,
>
>In xen-4.3.0/tools/qemu-xen-traditional/hw/pt-graphics.c,  setup_vga_pt
calls get_vgabios
>to get vgabios of passed->through VGA adapter, but get_vgabios only read
bios from /dev/mem,
>/dev/mem is domain 0’s memory device. /dev/mem >should only contain the
vgabios of primary
>VGA adapter of domain 0.
>
>So if I want to pass through secondary adapter of domain 0 to domain U.
setup_vga_pt cannot
>correctly setup VGABIOS for >domain U. Is this correct? Any comments are
appreciated.
>
>thanks
>huiming
This is only a problem if you are trying to pass the Dom0 secondary adapter
through as a
primary adapter to the DomU.  In this case the DomU will have the wrong VBios.

There is no problem if you are passing the Dom0 secondary adapter through as a
secondary
adapter to DomU.  In this case the emulated (Cirrus) VBios will be properly
copied to 0xc0000.

Thanks,
Kelly


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