Re: [Qemu-devel] [PATCH] pci: implement bridge filtering

[Michael S. Tsirkin]

On Tue, Sep 20, 2011 at 04:09:23PM +0800, Wen Congyang wrote:
> At 09/14/2011 09:48 AM, Wen Congyang Write:
> > At 09/05/2011 02:13 AM, Michael S. Tsirkin Write:
> >> Support bridge filtering on top of the memory
> >> API as suggested by Avi Kivity:
> >>
> >> Create a memory region for the bridge's address space.  This region is
> >> not directly added to system_memory or its descendants.  Devices under
> >> the bridge see this region as its pci_address_space().  The region is
> >> as large as the entire address space - it does not take into account
> >> any windows.
> >>
> >> For each of the three windows (pref, non-pref, vga), create an alias
> >> with the appropriate start and size.  Map the alias into the bridge's
> >> parent's pci_address_space(), as subregions.
> >>
> >> Signed-off-by: Michael S. Tsirkin <address@hidden>
> >> ---
> >>
> >> The below seems to work fine for me so I applied this.
> >> Still need to test bridge filtering, any help with this
> >> appreciated.
> >>
> > 
> > 
> > I test bridge filtering, and the BAR still can be visible on guest even if
> > I change the memory region.
> 
> Hi Michael S. Tsirkin:
> I test pci bridge filtering on real hardware, and I find that I can mmap
> the resource after I change the memory base and memory limit(The BAR should
> be not visible on OS after changing the memory region).
> 
> So I try to write and read to the BAR. Here is my test result:
> 1. Before changing the pci bridge's memory region, I can read and write to 
> the memory, and
>    I can get the same value that I write.
> 
> 2. After changing the pci bridge's memory region, I can still read and write 
> to the memory,
>    but it is very slow, and I can not get the same value that I write(The 
> value is always 0).
> 
> Does this result means that pci bridge filtering works fine?
> 
> Thanks
> Wen Congyang

Sounds more or less right except I expect to get ffffffff
and not 0. Avi, any idea?

-- 
MST