linux-kernel - Re: [PATCH v2] KVM: arm64: ptdump: Don't test PTE

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Message-ID: <8683495e-da79-4746-b6da-52164cdc031d@arm.com>
Date: Thu, 14 Aug 2025 10:28:47 +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>, Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2] KVM: arm64: ptdump: Don't test PTE_VALID alongside
 other attributes



On 09/08/25 7:23 PM, Wei-Lin Chang wrote:
> The attribute masks and test values in the ptdump code are meant for
> individual attributes, however for stage-2 ptdump we included PTE_VALID
> while testing for R, W, X, and AF. This led to some confusion and the
> flipped output for the executable attribute.
> 
> Remove PTE_VALID from all attribute masks and values so that each test
> matches only the relevant bits.
> 
> Additionally, the executable attribute printing is updated to align with
> stage-1 ptdump, printing "NX" for non-executable regions and "x " for
> executable ones.
> 
> Suggested-by: Anshuman Khandual <anshuman.khandual@....com>
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Suggested-by: Sebastian Ene <sebastianene@...gle.com>
> Signed-off-by: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>
> ---
> Tested on QEMU.
> 
> Changes in v2, thanks to those listed in the Suggested-by tags:
>   - remove PTE_VALID from .mask and .val
>   - make executable attribute output format identical to stage-1 ptdump
>   - Link to v1: https://lore.kernel.org/kvmarm/20250802104021.3076621-1-r09922117@csie.ntu.edu.tw/
> ---
>  arch/arm64/kvm/ptdump.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index 098416d7e5c25..dc5acfb00af91 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -32,23 +32,23 @@ static const struct ptdump_prot_bits stage2_pte_bits[] = {
>  		.set	= " ",
>  		.clear	= "F",
>  	}, {
> -		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
> -		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
>  		.set	= "R",
>  		.clear	= " ",
>  	}, {
> -		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
> -		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
>  		.set	= "W",
>  		.clear	= " ",
>  	}, {
> -		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
> -		.val	= PTE_VALID,
> -		.set	= " ",
> -		.clear	= "X",
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> +		.val	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> +		.set	= "NX",
> +		.clear	= "x ",
>  	}, {
> -		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
> -		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF,
>  		.set	= "AF",
>  		.clear	= "  ",
>  	}, {

LGTM and consistent with Stage-1.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>