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

[Wen Congyang <wency@cn.fujitsu.com>]

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 <mst@redhat.com>
>> ---
>>
>> 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