Re: [Qemu-devel] [RFC PATCH qemu 3/4] memory: Share flat views and dispatch trees between address spaces

[Alexey Kardashevskiy]

On 12/09/17 01:30, Paolo Bonzini wrote:
> On 11/09/2017 14:08, Alexey Kardashevskiy wrote:
>>> Ok, this makes sense.  Maybe it should be a flatview rather than an
>>> AddressSpaceDispatch (a FlatView is essentially a list of
>>> MemoryRegionSections; attaching the ASD to the FlatView is more or less
>>> an implementation detail).
>> The helpers I converted from AddressSpace to AddressSpaceDispatch do use
>> dispatch structure only and do not use FlatView so it seemed logical.
> 
> Understood, but from a design POV FlatView makes more sense.
> 
>> btw this address_space in MemoryRegionSection - it does not seem to make
>> much sense in the PhysPageMap::sections array, it only makes sense when
>> MemoryRegionSection uses as a temporary object when calling listeners. Will
>> it make sense if we enforce MemoryRegionSection::address_space to be NULL
>> in the array and not NULL when used temporary?
> 
> memory_region_section_get_iotlb needs to access the AddressSpaceDispatch
> for sections stored in the PhysPageMap array, because
> memory_region_section_get_iotlb uses the ASD to compute the section index.

Ohhh, not extremely trivial, out of curiosity - is that iotlb encoding
described anywhere?

Anyway, this can be simplified (or rather made more straightforward?) -
tlb_set_page_with_attrs() can calculate the section index and pass it to
memory_region_section_get_iotlb(). Still does not make much sense? It just
looks quite useless to keep that address_space pointer alive just for one
case which can easily avoid using this pointer.


-- 
Alexey