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
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