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Date: Thu, 3 Apr 2014 10:36:55 +0800
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Subject: Re: [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect
From: Liu ping fan <kernelfans@gmail.com>
To: Alexander Graf <agraf@suse.de>
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Cc: kvm-devel <kvm@vger.kernel.org>, kvm-ppc <kvm-ppc@vger.kernel.org>,
 Paul Mackerras <paulus@samba.org>,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
 linuxppc-dev@lists.ozlabs.org
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Hi Alex, could you help to pick up this patch? since  v3.14 kernel can
enable numa fault for powerpc.

Thx,
Fan

On Mon, Jan 27, 2014 at 5:11 PM, Alexander Graf <agraf@suse.de> wrote:
>
> On 21.01.2014, at 10:42, Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> wrote:
>
>> Liu Ping Fan <kernelfans@gmail.com> writes:
>>
>>> To make sure that on host, the pages marked with _PAGE_NUMA result in a fault
>>> when guest access them, we should force the checking when guest uses hypercall
>>> to setup hpte.
>>>
>>> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
>>
>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>>
>> 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. This patch does that.
>
> So what happens next? We insert a page into the HTAB without HPTE_V_VALID set, so the guest will fail to use it. If the guest does an H_READ on it it will suddenly turn to V_VALID though?
>
> I might need a crash course in the use of HPTE_V_ABSENT.
>
>
> Alex
>