[OpenBIOS] Back at it again( PCI Passthrough )
Mark Cave-Ayland
mark.cave-ayland at ilande.co.uk
Mon May 7 08:38:45 CEST 2018
On 07/05/18 01:21, Tarl Neustaedter wrote:
> For what it's worth:
>
> On 2018-May-6 20:12 , Joe van Tunen wrote:
>> b(lit) 0xff
>> and
>> my-space
>> +
>> (unnamed-fcode) [0xa08]
>> b(lit) 0x6
>> and
>> b(lit) 0x4
>> =
>
> That sequence is probably testing a BAR for 64-bit capability. Bits 1-2
> are the type of memory referenced by a BAR (0=IO, 1=32-bit mem, 2=64-bit
> mem).
>
> https://en.wikipedia.org/wiki/PCI_configuration_space#Bus_enumeration
>
> Does QEMU do something funny with 64-bit BARs? An NVIDIA card is almost
> certain to have 64-bit addressing in at least one BAR, and if QEMU
> doesn't support it, bad things may be happening.
I had to fix this for my virtio patches: OpenBIOS does support 64-bit
BARs but only maps devices into 32-bit addresses (i.e. the top 32-bits
are always 0).
ATB,
Mark.
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