linux-kernel - Re: [PATCH v6 1/4] KVM: arm64: Introduce cache maintenance callbacks for guest stage-2

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Message-ID: <0af45a89-03cd-ac0d-9fa2-7f57eb828c86@huawei.com>
Date:   Thu, 17 Jun 2021 17:43:23 +0800
From:   "wangyanan (Y)" <wangyanan55@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Will Deacon <will@...nel.org>, Quentin Perret <qperret@...gle.com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        <kvmarm@...ts.cs.columbia.edu>,
        <linux-arm-kernel@...ts.infradead.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Gavin Shan <gshan@...hat.com>, <wanghaibin.wang@...wei.com>,
        <zhukeqian1@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [PATCH v6 1/4] KVM: arm64: Introduce cache maintenance callbacks
 for guest stage-2

Hi Marc,

On 2021/6/17 16:44, Marc Zyngier wrote:
> On Thu, 17 Jun 2021 09:22:51 +0100,
> "wangyanan (Y)" <wangyanan55@...wei.com> wrote:
>>
>>
>> On 2021/6/17 16:03, Marc Zyngier wrote:
>>> On Thu, 17 Jun 2021 07:48:29 +0100,
>>> "wangyanan (Y)" <wangyanan55@...wei.com> wrote:
>>>> Hi Marc,
>>>>
>>>> On 2021/6/16 21:21, Marc Zyngier wrote:
>>>>> Hi Yanan,
>>>>>
>>>>> On Wed, 16 Jun 2021 10:51:57 +0100,
>>>>> Yanan Wang <wangyanan55@...wei.com> wrote:
>>>>>> To prepare for performing guest CMOs in the fault handlers in pgtable.c,
>>>>>> introduce two cache maintenance callbacks in struct kvm_pgtable_mm_ops.
>>>>>>
>>>>>> The new callbacks are specific for guest stage-2, so they will only be
>>>>>> initialized in 'struct kvm_pgtable_mm_ops kvm_s2_mm_ops'.
>>>>>>
>>>>>> Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
>>>>>> ---
>>>>>>     arch/arm64/include/asm/kvm_pgtable.h | 7 +++++++
>>>>>>     1 file changed, 7 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
>>>>>> index c3674c47d48c..302eca32e0af 100644
>>>>>> --- a/arch/arm64/include/asm/kvm_pgtable.h
>>>>>> +++ b/arch/arm64/include/asm/kvm_pgtable.h
>>>>>> @@ -44,6 +44,11 @@ typedef u64 kvm_pte_t;
>>>>>>      *			in the current context.
>>>>>>      * @virt_to_phys:	Convert a virtual address mapped in the current context
>>>>>>      *			into a physical address.
>>>>>> + * @flush_dcache:	Clean data cache for a guest page address range before
>>>>>> + *			creating the corresponding stage-2 mapping.
>>>>> Please don't reintroduce the word 'flush'. We are really trying to
>>>>> move away from it as it doesn't describe what we want to do.
>>>> I agree with this. I intended to make the names short and laconic, but this
>>>> missed the information about the callback's actual behaviors.
>>>>> Here this
>>>>> should be 'clean_invalidate_dcache' which, despite being a mouthful,
>>>>> describe accurately what we expect it to do.
>>>> Sure, I will change the name as you suggested.
>>>>> The comment is also missing the invalidate part, and we shouldn't
>>>>> assume that this is only used for S2 mapping.
>>>> Ok, will refine the comment. I think something like"Clean and invalidate the
>>>> date cache for the specified memory address range" may be generic enough.
>>>>>> + * @flush_icache:	Invalidate instruction cache for a guest page address
>>>>>> + *			range before creating or updating the corresponding
>>>>>> + *			stage-2 mapping.
>>>>> Same thing here; this should be 'invalidate_icache', and the comment
>>>>> cleaned up.
>>>> Thanks, I will also correct this part.
>>>>
>>>> Besides the callback names and comments, is there anything else that still
>>>> needs some adjustment in the other three patches? :)
>>> It looks pretty good so far, much nicer than the previous versions.
>>>
>>> I have a small nit on the last patch, which should be dead easy to
>>> address. I'm currently running a bunch of tests, hopefully nothing bad
>>> will come out of it.
>>>
>>> If you respin it shortly, that nothing fails, and unless someone
>>> shouts, I'll queue it for -next.
>> It would be nice, thanks!
>> I will address the nit and respin the series soon.
> By the way, what the status of your selftest series that originally
> came with this series? Are you planning to respin it? It would be
> useful to have something that checks for regressions, and that series
> did seem to do the trick.
Actually they have already gone into upstream, since v5.13-rc1. :)
The path is tools/testing/selftests/kvm/kvm_page_table_test.c, so it
will be much convenient to test a 5.13 kernel, you can also have a try.

I am using the original test data from v3 in the cover-letter because
I think the test results will be almost the same with a different kernel.

Thanks,
Yanan
.
> Thanks,
>
> 	M.
>