Re: [Qemu-devel] [PATCH 2/3] exec: simplify address_space_get_iotlb_entry

[Michael S. Tsirkin]

On Fri, Jun 09, 2017 at 09:58:47AM +0800, Peter Xu wrote:
> > > The problem is that when I was fixing the problem that vhost had with
> > > PT (a764040, "exec: abstract address_space_do_translate()"), I did
> > > broke the IOTLB translation a bit (it was using page masks). IMHO we
> > > need to fix it first for correctness (patch 1/2).
> > > 
> > > For patch 3, if we can have Jason's patch to allow dynamic
> > > iommu_platform switching, that'll be the best, then I can rewrite
> > > patch 3 with the switching logic rather than caching anything. But
> > > IMHO that can be separated from patch 1/2 if you like.
> > > 
> > > Or do you have better suggestion on how should we fix it?
> > > 
> > > Thanks,
> > 
> > Can we drop masks completely and replace with length? I think we
> > should do that instead of trying to fix masks.
> 
> Do you mean to modify IOMMUTLBEntry.addr_mask into length?

I think it's better than alternatives.

> Again, I am not sure this is good... At least we need to get ack from
> David since spapr should be the initial user of it, and possibly also
> Alex since vfio should be assuming that (IIUC both in QEMU and kernel)
> addr_mask is page masks rather than arbirary length.
> 
> (CC Alex)
> 
> Thanks,

Callbacks that need powers of two can easily split up the range.


> -- 
> Peter Xu