Re: [SeaBIOS] [PATCH] acpi: hide 64-bit PCI hole for Windows XP
On Thu, Aug 08, 2013 at 10:51:59AM +0200, Gerd Hoffmann wrote:
On 08/08/13 10:22, Michael S. Tsirkin wrote:
> On Thu, Aug 08, 2013 at 09:57:39AM +0200, Gerd Hoffmann wrote:
>> Hi,
>>
>>>> Huh? The 32bit window is sized according to the installed memory.
>>>> That
>>>> logic is in seabios and you'll try to move it to qemu, using
pci-info.
>>>> It wasn't in qemu before ...
>>>
>>> The logic is in hw/i386/pc_piix.c and always was.
>>
>> What exactly you are refering to?
>
> pc_init1 which picks addresses and passes them on to
> i440fx_init.
Yep. qemu figured where it wants map memory. The unused 32bit address
space goes into the pci hole. cmos memory size is set accordingly.
seabios gets the memory size from cmos, then it knows where the pci hole
starts. seabios rounds it up (i.e. may leave some of it unused) to be
able to cover the complete hole with a single mtrr entry, but that isn't
a issue and can be changed if needed. The mtrr thing is more or less
cosmetical anyway in a virtual machine.
>> Memory configuration is in the cmos, firmware can figure where it can
>> place pci devices from that. There is no need for a new interface.
>
> The assumption being that whatever is not memory is PCI?
> I'm not sure that's right.
Maybe not in general, but I'm pretty sure for the x86 chipsets we are
emulating it is.
I think this is the basic question.
Speaking about PIIX:
http://download.intel.com/design/chipsets/datashts/29054901.pdf
it only supported 1G RAM and 32 bit PCI.
What happened with RAM below 1G is this:
top of RAM to 0xfec00000 is PCI - this is emulated correctly
fec10000 to ffe00000 is PCI - this is not emulated correctly
What happens with RAM >1G is all PV, it doesn't exist
on real hardware.
Re-adding qemu-devel. Can you please keep it Cc'd?
--
MST