Re: missing kvm smp tlb flush in invlpg

Izik Eidus
2009-03-15T20:11:35Z

Marcelo Tosatti wrote:
> On Thu, Mar 12, 2009 at 06:18:43PM +0100, Andrea Arcangeli wrote:
>
>> From: Andrea Arcangeli <aarcange@redhat.com>
>>
>> While looking at invlpg out of sync code with Izik I think I noticed a
>> missing smp tlb flush here. Without this the other cpu can still write
>> to a freed host physical page. tlb smp flush must happen if
>> rmap_remove is called always before mmu_lock is released because the
>> VM will take the mmu_lock before it can finally add the page to the
>> freelist after swapout. mmu notifier makes it safe to flush the tlb
>> after freeing the page (otherwise it would never be safe) so we can do
>> a single flush for multiple sptes invalidated.
>>
>
> I think this fix is more expensive than it needs to be, but better than
> being unsafe for now.
>
> Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
>
>
What about inside mmu_set_spte():
} else if (pfn != spte_to_pfn(*shadow_pte)) {
pgprintk("hfn old %lx new %lx\n",
spte_to_pfn(*shadow_pte), pfn);
rmap_remove(vcpu->kvm, shadow_pte);
} else

Doesnt this required tlb flush for all the cpus as well?