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xen-devel
RE: [Xen-devel] Taken fault at bad CS c000...
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: 2007年2月15日 16:40
>On 15/2/07 08:36, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
>
>> 2) No permission on I/O ports (0xCF8/0xCFC, 0x20e0, 0x20e4)
>> which is weird:
>> Seems that this version of VGA bios will try to scan PCI bus.
>> 0x20e0/0x20e4 is the I/O BAR configured for integrated graphics
>> controller. However I printed all sys_ioperm, and found that Xorg
>> only requests for [0x0-0x3ff],[0x40-0x43],[0x60-0x63]. Then each
>> time when above ports are accessed within VM86 mode,
>> guest_io_okay will fail since related bitmap bits are all 1s. So I'm
>> interested that why X-windows can still work under such case. Do
>> you know any path to enable I/O ports specially for VM86 mode?
>
>It may be that the X Server fixes up the faults. I'm pretty sure it can do
>various bits of fixup emulation.
>
> -- Keir
OK, maybe X server will turn to legacy VGA ports for fixup...
So, will VM86 mode also utilize 4g segment? If yes, we can remove
the print for vm86. Or else, the whole seg fixup can be skipped for
vm86 then. :-)
Thanks,
Kevin
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