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

[Razvan Cojocaru <rzvncj@xxxxxxxxx>]

Hello, and thanks for your comments.

> > +    if ( v->arch.hvm_vmx.mem_event_emulate )
> Lack of mem event support for AMD processors will be fixed as soon as someone 
> with interest (and time!) gets going. I don't recall anything fundamental 
> standing in the way.
>
> So it's best if you lift this field into the generic hvm level.
That would make it v->arch.mem_event_emulate, correct?

> Tim's point is that you won't get all the mem events, because the instruction 
> can easily touch multiple pages. It's a question that addresses the need for 
> this patch in the first place.
Yes, I did get Tim's point. Sorry if I haven't been able to make that as 
clear as I should have in my reply to Tim's email.
> One potential (hairy) fix is to have all get_page_from_gfn check for and emit a 
> mem event. It's a bit of rat hole, because we'll need to pass the intended 
> permissions down the stack, check against mem event status, etc etc. It will 
> help extend mem event to catch all hypervisor-based accesses that currently it 
> mostly can't, as well as foreign mappings. It's certainly not for the faint of 
> heart.
Fortunately, for the purposes of my patch, the simple solution is enough.

> > +#define MEM_EVENT_FLAG_EMULATE      (1 << 5) /* Emulate the instruction that 
> > caused the current mem_event */
> Line overflow, better stack the comment on top
No problem.

Thank you,
Razvan Cojocaru

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel