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Re: [Xen-devel] [PATCH v1] x86/hvm: Generic instruction re-execution mechanism for execute faults

On Wed, Dec 19, 2018 at 04:49:43PM +0000, Alexandru Stefan ISAILA wrote:
> On 27.11.2018 13:32, Roger Pau Monné wrote:
> > Would it be possible to add some kind of flag to the emulator to
> > signal whether p2m restrictions should be enforced/ignored?
> > hvmemul_acquire_page seems like a suitable place, but I'm not that
> > familiar with the emulator.
> > 
> > Then you could generate vm events from the emulator itself, which
> > AFAICT is the only way to handle this instruction execution issue.
> I've been testing what place would be the best to have the emulator send 
> a event and it turns out the hvmemul_acquire_page is not ok. What worked 
> form me was having the emulator send write access violations from 
> hvmemul_map_linear_addr(). Here I can get the gfn, gla and offset for 
> the event.
> For the exec access violation I've tried to send events from 
> hvmemul_insn_fetch() but there is a problem to get the same variables 
> for the event. Is there a way to go around and get those params for the 
> event? Any thoughts are appreciated.

You have the IP in hvmemul_insn_fetch, can't you get the gfn from
there? Either directly or by translating the gla to a gfn if the guest
is running with paging enabled?


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