Re: [Qemu-devel] [PATCH rebased for-1.8] i386: pc: align gpa<->hpa on 1GB boundary (v6)

[Paolo Bonzini]

Il 28/11/2013 11:26, Michael S. Tsirkin ha scritto:
> On Mon, Nov 25, 2013 at 06:43:13PM +0100, Paolo Bonzini wrote:
>> v2: condition enablement of new mapping to new machine types (Paolo)
>> v3: fix changelog
>> v4: rebase
>> v5: ensure alignment of piecetwo on 2MB GPA (Igor)
>>     do not register zero-sized piece-one    (Igor)
>> v6: fix memory leak                         (Igor)
>>     fix integer overflow                    (Igor)
>>
>> ----
>>
>> Align guest physical address and host physical address
>> beyond guest 4GB on a 1GB boundary.
>>
>> Otherwise 1GB TLBs cannot be cached for the range.
>>
>> Signed-off-by: Marcelo Tosatti <address@hidden>
>> [Reorganize code, keep same logic. - Paolo]
>> Signed-off-by: Paolo Bonzini <address@hidden>
>> ---
> 
> Applied, thanks.

As discussed offlist, I'm not sure anymore that this is the right
approach to the problem.  No doubt it is very clever, in that it is
absolutely transparent to the guest.  However, the non-contiguous
mapping of ram_addr_t makes it more complex to associate the right NUMA
policy to the ranges.

If we could make a small guset visible change, it would be simpler to
always make the PCI hole 1GB in size; it is currently 256MB for i440FX
and 1.25GB for q35.  We can take a look as soon as the SeaBIOS patches
are in to use QEMU-built ACPI tables.

Paolo