Re: [PATCH v5 4/6] KVM: arm64: Provide invalidate_icache_range at non-VHE EL2

From: Marc Zyngier <maz@kernel.org>
To: Yanan Wang <wangyanan55@huawei.com>
Cc: kvm@vger.kernel.org, Will Deacon <will@kernel.org>,
	linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 4/6] KVM: arm64: Provide invalidate_icache_range at non-VHE EL2
Date: Wed, 02 Jun 2021 11:22:56 +0100	[thread overview]
Message-ID: <875yyw1s73.wl-maz@kernel.org> (raw)
In-Reply-To: <20210415115032.35760-5-wangyanan55@huawei.com>

On Thu, 15 Apr 2021 12:50:30 +0100,
Yanan Wang <wangyanan55@huawei.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@huawei.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.

	M.

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