Patch for MS Hyper V (virtualization)

[John Baldwin]

On Monday 06 April 2009 1:07:38 pm Ivan Voras wrote:
> 2009/4/6 John Baldwin <jhb at freebsd.org>:
> > On Sunday 05 April 2009 12:23:39 pm Sergey Babkin wrote:
> 
> > Hmm, the problem is we need to be able to write to BARs to size them.  Any 
OS
> > needs to be able to do this to know what address space regions are being
> > decoded by devices.  We can't avoid writing to BARs.
> 
> I have only vague idea what BARs are and if it's the correct diagnosis
> in this case, but the fact is that other operating systems (Windows,
> Linux tested) work, so either there is a way around it or the original
> premise is wrong-ish.

Every OS writes to BARs to size them during boot.  It's the defined procedure 
for sizing them.  A BAR is a base address register, and it is how a PCI 
device gets memory and I/O port resources.  OS (or BIOS) writes a starting 
address into the register to tell the PCI device where a given 
resource "starts".

-- 
John Baldwin