Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path

Avi Kivity
2010-04-12T12:49:21Z

On 04/12/2010 03:22 PM, Xiao Guangrong wrote:
>
>> But kvm_mmu_zap_page() will only destroy sp == tpos == pos; n points at
>> pos->next already, so it's safe.
>>
>>
> kvm_mmu_zap_page(sp) not only zaps sp but also zaps all sp's unsync children
> pages, if n is just sp's unsyc child, just at the same hlist and just behind sp,
> it will crash. :-)
>

Ouch. I see now, thanks for explaining.

One way to fix it is to make kvm_mmu_zap_page() only zap the page it is
given, and use sp->role.invalid on its children. But it's better to fix
it now quickly and do the more involved fixes later.

Just change the assignment to a 'goto restart;' please, I don't like
playing with list_for_each internals.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.