Re: [PATCH] KVM: SVM: fix random segfaults with NPT enabled

Avi Kivity
2008-08-27T16:49:31Z

Joerg Rodel wrote:
>> Meanwhile, I applied the patch, but I'm very worried about this.
>>
>
> Yes, we are also worried. Another question is why this only happens with
> NPT. The SoftMMU code should also fail with shadow paging if there is a
> bug.
>

Slightly different paths -- direct_map vs page_fault. Also, with npt,
all cpus will access the same pte that's being modified; without npt,
faults on the same page will result in different ptes being
instantiated, as each access will be from a different guest pte.

Maybe we should turn on the dirty bit in the instantiated ptes -- that
will reduce the processor's mucking about with them.

--
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