Re: [Xen-devel] [PATCH 00/11] Alternate p2m: support multiple copies of host p2m

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.01.15 at 18:35, <edmund.h.white@xxxxxxxxx> wrote:
> On 01/14/2015 03:28 AM, Tamas K Lengyel wrote:
>> At the mem_access trap point you can swap in an altp2m where the
>> gfn->mfn mapping is the one where the breakpoints are hidden,
>> singlestep, then swap the original p2m back. While this approach still
>> has some overhead because of the use of singlestepping, it is going to
>> be faster then what you currently have to do, which is removing all
>> breakpoints, singlestep, then put breakpoints back. Now it would just
>> be a matter of swapping a single pointer.
> 
> Right. The key observation is that at any single point in time, a given
> hardware thread can be fetching an instruction or reading data, but not
> both.

Fine, as long as an instruction reading itself isn't going to lead to
a live lock.

Jan


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