Re: [PATCH -v2] Monitor command: pfa2hva, translate guest physical address to host virtual address

[Avi Kivity <avi@redhat.com>]

On 11/11/2010 02:56 AM, Huang Ying wrote:
> On Thu, 2010-11-11 at 00:49 +0800, Anthony Liguori wrote:
> >  On 11/10/2010 02:34 AM, Avi Kivity wrote:
> >  >>  Why the gpa ->   hva mapping is not
> >  >>  consistent for RAM if -mempath is not used?
> >  >
> >  >  Video RAM in the range a0000-bffff and PCI mapped RAM can change gpas
> >  >  (while remaining in the same hva).
> >  >
> >  >  Even for ordinary RAM, which doesn't normally change gpa/hva, I'm not
> >  >  sure we want to guarantee that it won't.
> >
> >  We can't universally either.  Memory hot remove potentially breaks the
> >  mapping and some non-x86 architectures (like ARM) can alias RAM via a
> >  guest triggered mechanism.
>
> Thanks for clarification. Now I think we have two options.
>
> 1) Clearly mark gpa2hva (pfa2hva now, should renamed to gpa2hva) as a
> testing only interface, and should be used only on restricted
> environment (normal memory, without hot-remove, maybe only on x86).
>
> 2) Find some way to lock the gpa ->  hva mapping during operating. Such
> as gpa2hva_begin and gpa2hva_end and lock the mapping in between.
>
> I think 2) may be possible. But if there are no other users, why do that
> for a test case? So I think 1) may be the better option.
>

3) Move the poisoning code into qemu, so the command becomes

    posison-address <addr>

(though physical addresses aren't stable either)

4) Use -mempath on /dev/shm and poison a page in the backing file

(if poisoning works on tmpfs)

-- 
error compiling committee.c: too many arguments to function