[PATCH v3] powerpc: kvm: make _PAGE_NUMA take effect

[Liu ping fan]

On Fri, Apr 11, 2014 at 10:03 PM, Alexander Graf <agraf at suse.de> wrote:
>
> On 11.04.2014, at 13:45, Liu Ping Fan <pingfank at linux.vnet.ibm.com> wrote:
>
>> When we mark pte with _PAGE_NUMA we already call mmu_notifier_invalidate_range_start
>> and mmu_notifier_invalidate_range_end, which will mark existing guest hpte
>> entry as HPTE_V_ABSENT. Now we need to do that when we are inserting new
>> guest hpte entries.
>
> What happens when we don't? Why do we need the check? Why isn't it done implicitly? What happens when we treat a NUMA marked page as non-present? Why does it work out for us?
>
> Assume you have no idea what PAGE_NUMA is, but try to figure out what this patch does and whether you need to cherry-pick it into your downstream kernel. The description as is still is not very helpful for that. It doesn't even explain what really changes with this patch applied.
>
Yeah.  what about appending the following description?  Can it make
the context clear?
"Guest should not setup a hpte for the page whose pte is marked with
_PAGE_NUMA, so on the host, the numa-fault mechanism can take effect
to check whether the page is placed correctly or not."

>>
>> Signed-off-by: Liu Ping Fan <pingfank at linux.vnet.ibm.com>
>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>> ---
>> v3:
>>  rebased onto Alex's tree, branch kvm-ppc-next
>>  substitue commit log with the more clear description in Aneesh's reply (thanks, Aneesh)
>> ---
>> arch/powerpc/kvm/book3s_hv_rm_mmu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
>> index 1d6c56a..1117525 100644
>> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
>> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
>> @@ -234,7 +234,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
>>               pte_size = psize;
>>               pte = lookup_linux_pte_and_update(pgdir, hva, writing,
>>                                                 &pte_size);
>> -             if (pte_present(pte)) {
>> +             if (pte_present(pte)&&!pte_numa(pte)) {
>
> Spaces missing
>
Will fix,

Thx,
Fan