Re: [Xen-devel] [PATCH] passthru: Fix pci bar remapping for passthru devices

[Wei Wang2 <wei.wang2@xxxxxxx>]

Hi Yunhong
My testing shows that Linux guests will try to probe pci bar with MMIO being 
enabled. When I assign a broadcom NIC with 32MB MMIO a Linux guest, guest 
will hang after remapping a guest address "0xfe000000" to physical mmio. 
However, windows and BSD guests do not have this issue. They alway probe mmio 
size after disabling mmio. 
Thanks,
Wei

On Monday 20 July 2009 16:26:00 Jiang, Yunhong wrote:
> I assume guest should disable the MMIO in PCI_COMMAND before writing all
> "1"s to bar register. Otherwise, what will happen on native if guest try to
> access 0xFFFFFFF0? And if we do update the P2M, will it cause trouble to
> Xen HV?
>
> Thanks
> Yunhong Jiang
>
> xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote:
> > Hi,
> > When guest code tries to get the block size of mmio, it will write
> > all "1"s into pci bar register and then qemu will return all "0"s to
> > the don't care
> > bits in the emulated bar register to indicate the block size
> > to guest code.
> > In this case, we should not create p2m mapping in
> > pt_bar_reg_write() and
> > pt_exp_rom_bar_reg_write(). Attached patch fixes this issue,
> > additional comment can be found in the patch.
> >
> > Thanks,
> > Wei
> >
> > Signed-off-by: Wei Wang <wei.wang2@xxxxxxx>
> > --
> > AMD GmbH, Germany
> > Operating System Research Center
> >
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