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

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Date:   Thu, 17 Jun 2021 16:22:51 +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



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.

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