linux-kernel - Re: [PATCH] KVM: arm64: Fix unaligned addr case in mmu walking

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Date:   Wed, 3 Mar 2021 21:13:26 +0000
From:   Will Deacon <will@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Jia He <justin.he@....com>, kvmarm@...ts.cs.columbia.edu,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Gavin Shan <gshan@...hat.com>,
        Yanan Wang <wangyanan55@...wei.com>,
        Quentin Perret <qperret@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: Fix unaligned addr case in mmu walking

On Wed, Mar 03, 2021 at 07:07:37PM +0000, Marc Zyngier wrote:
> From e0524b41a71e0f17d6dc8f197e421e677d584e72 Mon Sep 17 00:00:00 2001
> From: Jia He <justin.he@....com>
> Date: Wed, 3 Mar 2021 10:42:25 +0800
> Subject: [PATCH] KVM: arm64: Fix range alignment when walking page tables
> 
> When walking the page tables at a given level, and if the start
> address for the range isn't aligned for that level, we propagate
> the misalignment on each iteration at that level.
> 
> This results in the walker ignoring a number of entries (depending
> on the original misalignment) on each subsequent iteration.
> 
> Properly aligning the address at the before the next iteration

"at the before the next" ???

> addresses the issue.
> 
> Cc: stable@...r.kernel.org
> Reported-by: Howard Zhang <Howard.Zhang@....com>
> Signed-off-by: Jia He <justin.he@....com>
> Fixes: b1e57de62cfb ("KVM: arm64: Add stand-alone page-table walker infrastructure")
> [maz: rewrite commit message]
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/20210303024225.2591-1-justin.he@arm.com
> ---
>  arch/arm64/kvm/hyp/pgtable.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 4d177ce1d536..124cd2f93020 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -223,7 +223,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
>  		goto out;
>  
>  	if (!table) {
> -		data->addr += kvm_granule_size(level);
> +		data->addr = ALIGN(data->addr, kvm_granule_size(level));
>  		goto out;
>  	}

If Jia is happy with it, please feel free to add:

Acked-by: Will Deacon <will@...nel.org>

Will