[PATCH v4 5/7] ARM: KVM: rework HYP page table freeing

[Christoffer Dall]

On Fri, Apr 26, 2013 at 9:45 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On 26/04/13 12:05, Catalin Marinas wrote:
>> On Fri, Apr 12, 2013 at 07:12:05PM +0100, Marc Zyngier wrote:
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index bfc5927..7464824 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>> ...
>>> +static void clear_pmd_entry(pmd_t *pmd)
>>> +{
>>> +    pte_t *pte_table = pte_offset_kernel(pmd, 0);
>>> +    pmd_clear(pmd);
>>> +    pte_free_kernel(NULL, pte_table);
>>> +    put_page(virt_to_page(pmd));
>>> +}
>> ...
>>>  static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
>>
>> Is there a chance that this function (or the other unmapping function
>> for Hyp pages) is called on an active stage 2 table (VTTBR pointing to
>> this pgd)? If yes, than you probably have to follow the mmu_gather
>> mechanism of freeing page table pages to avoid speculative loads.
>> Basically flushing the TLB between pmd_clear and pte_free_kernel.
>
> Blah. You're right, we got it wrong.
>
> We need to move our TLB invalidation out of kvm_unmap_hva_handler, and
> put it in clear_pmd_entry. I'll cook a patch.
>
> Thanks for reviewing.
>
Ah, because clean_pmd_entry doesn't  flush stage2 TLB, that's the issue?