linux-kernel - Re: [PATCH v5 4/6] KVM: arm64: Provide invalidate_icache

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Date:   Thu, 3 Jun 2021 20:34:58 +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 v5 4/6] KVM: arm64: Provide invalidate_icache_range at
 non-VHE EL2

Hi Marc,

On 2021/6/2 18:22, Marc Zyngier wrote:
> On Thu, 15 Apr 2021 12:50:30 +0100,
> Yanan Wang <wangyanan55@...wei.com> wrote:
>> We want to move I-cache maintenance for the guest to the stage-2
>> page table code for performance improvement. Before it can work,
>> we should first make function invalidate_icache_range available
>> to non-VHE EL2 to avoid compiling or program running error, as
>> pgtable.c is now linked into the non-VHE EL2 code for pKVM mode.
>>
>> In this patch, we only introduce symbol of invalidate_icache_range
>> with no real functionality in nvhe/cache.S, because there haven't
>> been situations found currently where I-cache maintenance is also
>> needed in non-VHE EL2 for pKVM mode.
>>
>> Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
>> ---
>>   arch/arm64/kvm/hyp/nvhe/cache.S | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/hyp/nvhe/cache.S b/arch/arm64/kvm/hyp/nvhe/cache.S
>> index 36cef6915428..a125ec9aeed2 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/cache.S
>> +++ b/arch/arm64/kvm/hyp/nvhe/cache.S
>> @@ -11,3 +11,14 @@ SYM_FUNC_START_PI(__flush_dcache_area)
>>   	dcache_by_line_op civac, sy, x0, x1, x2, x3
>>   	ret
>>   SYM_FUNC_END_PI(__flush_dcache_area)
>> +
>> +/*
>> + *	invalidate_icache_range(start,end)
>> + *
>> + *	Ensure that the I cache is invalid within specified region.
>> + *
>> + *	- start   - virtual start address of region
>> + *	- end     - virtual end address of region
>> + */
>> +SYM_FUNC_START(invalidate_icache_range)
>> +SYM_FUNC_END(invalidate_icache_range)
> This is a good indication that something is really wrong.
>
> If you were to provide cache management callbacks as part of the
> mm_ops themselves (or a similar abstraction), you wouldn't have to do
> these things.
Yes, we definitely don't need this work if we do that.

Thanks,
Yanan
>
> 	M.
>