Re: [Query] Flow of PCI device dedicated to a domU

[Simon Martin <furryfuttock@gmail.com>]

Hello Simon,

Tuesday, July 22, 2014, 4:56:57 PM, you wrote:

> Hello Stefano,

>> The basic mechanism is that Xen assigns the PCI root complex/host
>> bridge to Dom0. Dom0 walks the bus and finds out the devices available.

>> When the user assigns a PCI device to a VM, the toolstack (xl/libxl)
>> issues hypercalls to remap interrupts and MMIO regions of that device
>> into the guest VM.

> I am currently trying writing my own PCI front to access directly a
> PCI device from my PV guest.

> If I read this correctly you are saying that the MMIO region is
> already mapped into my domain by xl? So when I go and read the BAR
> register from the PCI configuration I can just go and access it
> directly or do I have to update the VA mapping?

Just a clarification here, when I say "go and access it" what I meant
to say was "go and access directly in my PV the memory at the BAR
address".

-- 
Best regards,
 Simon                            mailto:furryfuttock@gmail.com