On 11/12/2010 03:16 AM, Huang Ying wrote:
On Thu, 2010-11-11 at 17:39 +0800, Avi Kivity wrote:
> 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)
Poisoning includes:
a) gva -> gpa
b) gpa -> hva
c) hva -> hpa
d) inject the MCE into host via some external tool
poison-address need to do b, c, d. Do you think it is good to do all
these inside qemu?
If d is not too complicated (an ioctl?), we might to it in qemu.
> 4) Use -mempath on /dev/shm and poison a page in the backing file
If we can poison a page in the backing file, how do we know the
corresponding gpa and hpa?
I think you currently can't know it's gpa (why do you want to?); the
upcoming NUMA enhancements should allow this (the plan is to have a file
per guest NUMA node, so we can tell the host what policy to apply for
that node).
gpa->hpa translation can be derived from /proc/pid/maps.
--
error compiling committee.c: too many arguments to function
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