Re: [PATCH V2] mem_event: Allow emulating an instruction that caused a page fault

[Razvan Cojocaru <rzvncj@gmail.com>]

> Ok, talking only about writes, we have the destination operand, plus all
> the pagetables (for setting Accessed bits) plus any stacks and TSSes
> needed in delivering faults; something like 32 pages for the full
> double-fault scenario.

I see, but then, even setting aside Andres' argument that having all 
possible events sent to userspace is far from trivial, doing so would 
completely cripple the monitored domain speed-wise. Imagine having 
userspace having to decide if it allows a write 32 times per one 
instruction.

Even with its limitations, this patch at least gives us a shot at 
looking at what the domain does with memory - the existing model 
(releasing the page completely to allow the write) is not fit for 
anything like this at all.

So far, between the requirements of reasonable demands on the domU, and 
satisfactory levels of control provided by the received mem_events, at 
least as far as writes go, the patch's done it's job quite nicely.

Thanks,
Razvan Cojocaru