Re: [Xen-devel] Inconsistent use of set_context_data()?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.16 at 14:22, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> what's the point of this being used by hvmemul_read() and
>> hvmemul_cmpxchg(), but (namely but not limited to) not by
>> hvmemul_write()?
> 
> To do introspection work, we sometimes need to modify the guest memory,
> and there are cases, namely during hibernate / resume of Windows guests,
> when we need to serve the "old" version of that memory to the current
> instruction reading from it for the process to work reliably.
> 
> The design choice here has been that the introspection application is
> smart enough to handle writes (after all, it is the one managing the
> buffer sent via vm_event reply), so it is intended behaviour.

Well - the confusing thing is that for cmpxchg it's the value to be
written which gets altered, not the value to be compared against,
i.e. it acts as if set_context_data() was also intended to be
present in hvmemul_write().

Jan


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