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

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Message-ID: <8340be12-cc80-8c2a-3597-ecba05eaf35a@huawei.com>
Date:   Thu, 17 Jun 2021 14:48:29 +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 2021/6/16 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? :)

Regards,
Yanan
.
>>    */
>>   struct kvm_pgtable_mm_ops {
>>   	void*		(*zalloc_page)(void *arg);
>> @@ -54,6 +59,8 @@ struct kvm_pgtable_mm_ops {
>>   	int		(*page_count)(void *addr);
>>   	void*		(*phys_to_virt)(phys_addr_t phys);
>>   	phys_addr_t	(*virt_to_phys)(void *addr);
>> +	void		(*flush_dcache)(void *addr, size_t size);
>> +	void		(*flush_icache)(void *addr, size_t size);
>>   };
>>   
>>   /**
> Thanks,
>
> 	M.
>