linux-kernel - Re: [PATCH] KVM: arm64: ptdump: Fix exec attribute printing

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Message-ID: <d72b7928-8646-4616-a8f0-96b9d9bbaf09@arm.com>
Date: Sun, 3 Aug 2025 19:33:04 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>,
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
 Joey Gouly <joey.gouly@....com>, Sebastian Ene <sebastianene@...gle.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu
 <yuzenghui@...wei.com>, Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>
Subject: Re: [PATCH] KVM: arm64: ptdump: Fix exec attribute printing



On 02/08/25 4:10 PM, Wei-Lin Chang wrote:
> Currently the guest stage-2 page table dump has the executable attribute
> printed in reverse, showing "X" for a non-executable region and showing
> " " for an executable one. This is caused by misjudgement of which
> string gets printed for the executable and non-executable case. Fix it
> by swapping the two strings.
> 
> Signed-off-by: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>
> ---
>  arch/arm64/kvm/ptdump.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index 098416d7e5c25..99fc13f1c11fb 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -44,8 +44,8 @@ static const struct ptdump_prot_bits stage2_pte_bits[] = {
>  	}, {
>  		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
>  		.val	= PTE_VALID,
> -		.set	= " ",
> -		.clear	= "X",
> +		.set	= "X",
> +		.clear	= " ",
>  	}, {
>  		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
>  		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,

Is not KVM_PTE_LEAF_ATTR_HI_S2_XN already in the reverse semantics aka
XN (Execute Never). Hence when KVM_PTE_LEAF_ATTR_HI_S2_XN macro is set
that means the entry is not executable and vice versa.