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

From: Marc Zyngier <maz@kernel.org>
To: Yanan Wang <wangyanan55@huawei.com>
Cc: Will Deacon <will@kernel.org>,
	"Quentin\ Perret" <qperret@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	<kvmarm@lists.cs.columbia.edu>,
	<linux-arm-kernel@lists.infradead.org>, <kvm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	Gavin Shan <gshan@redhat.com>, <wanghaibin.wang@huawei.com>,
	<zhukeqian1@huawei.com>, <yuzenghui@huawei.com>
Subject: Re: [PATCH v6 1/4] KVM: arm64: Introduce cache maintenance callbacks for guest stage-2
Date: Wed, 16 Jun 2021 14:21:23 +0100	[thread overview]
Message-ID: <87eed2lzcc.wl-maz@kernel.org> (raw)
In-Reply-To: <20210616095200.38008-2-wangyanan55@huawei.com>

Hi Yanan,

On Wed, 16 Jun 2021 10:51:57 +0100,
Yanan Wang <wangyanan55@huawei.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@huawei.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. Here this
should be 'clean_invalidate_dcache' which, despite being a mouthful,
describe accurately what we expect it to do.

The comment is also missing the invalidate part, and we shouldn't
assume that this is only used for S2 mapping.

> + * @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.

>   */
>  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.

-- 
Without deviation from the norm, progress is not possible.

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