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

[marc.zyngier@arm.com (Marc Zyngier)]

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.

	M.
-- 
Jazz is not dead. It just smells funny...