linux-kernel - Re: [PATCH] kvm: arm64: Properly align the end address of table walk

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Date:   Fri, 15 Jan 2021 10:23:35 +0000
From:   Will Deacon <will@...nel.org>
To:     Keqian Zhu <zhukeqian1@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        wanghaibin.wang@...wei.com, jiangkunkun@...wei.com
Subject: Re: [PATCH] kvm: arm64: Properly align the end address of table walk

On Fri, Jan 15, 2021 at 05:53:07PM +0800, Keqian Zhu wrote:
> When align the end address, ought to use its original value.
> 
> Fixes: b1e57de62cfb ("KVM: arm64: Add stand-alone page-table walker infrastructure")
> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.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 bdf8e55ed308..670b0ef12440 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -296,7 +296,7 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
>  	struct kvm_pgtable_walk_data walk_data = {
>  		.pgt	= pgt,
>  		.addr	= ALIGN_DOWN(addr, PAGE_SIZE),
> -		.end	= PAGE_ALIGN(walk_data.addr + size),
> +		.end	= PAGE_ALIGN(addr + size),
>  		.walker	= walker,

Hmm, this is a change in behaviour, no (consider the case where both 'addr'
and 'size' are misaligned)? The current code is consistent with the
kerneldoc in asm/kvm_pgtable.h, so I don't see the motivation to change it.

Did you hit a bug somewhere?

Will