From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Alexander Graf <agraf@suse.de>
Cc: kvm-devel <kvm@vger.kernel.org>,
kvm-ppc <kvm-ppc@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
Liu Ping Fan <kernelfans@gmail.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect
Date: Mon, 27 Jan 2014 21:27:08 +0530 [thread overview]
Message-ID: <87r47to1t7.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <72133741-22DA-4477-B89F-E9C978FA294F@suse.de>
Alexander Graf <agraf@suse.de> writes:
> On 27.01.2014, at 11:28, Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> wrote:
>
>> Alexander Graf <agraf@suse.de> writes:
>>
>>> 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?
>>
>> As per the guest the entry is valid, so yes an hread should return a
>> valid entry. But in real hpte we would mark it not valid.
>
> Ah, yes.
>
>>
>>>
>>> I might need a crash course in the use of HPTE_V_ABSENT.
>>
>> When guest tries to access the address, the host will handle the fault.
>>
>> kvmppc_hpte_hv_fault should give more info
>
> Thanks for the pointer. So we fault it in lazily. Is there any
> particular reason we can't do that on h_enter already? After all this
> just means an additional roundtrip because the guest is pretty likely
> to use the page it just entered, no?
We could get wrong numa fault information if we didn't do h_enter from
the right node from which we faulted.
-aneesh
next prev parent reply other threads:[~2014-01-27 15:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-21 8:15 [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect Liu Ping Fan
2014-01-21 9:42 ` Aneesh Kumar K.V
2014-01-27 9:11 ` Alexander Graf
2014-01-27 10:28 ` Aneesh Kumar K.V
2014-01-27 10:42 ` Alexander Graf
2014-01-27 15:57 ` Aneesh Kumar K.V [this message]
2014-01-27 10:41 ` Paul Mackerras
2014-04-03 2:36 ` Liu ping fan
2014-04-03 11:36 ` Alexander Graf
2014-04-03 11:38 ` Alexander Graf
2014-04-03 11:43 ` Alexander Graf
2014-04-07 7:42 ` Aneesh Kumar K.V
2014-04-07 8:36 ` Alexander Graf
2014-04-10 3:28 ` Liu ping fan
2014-04-10 10:02 ` Alexander Graf
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