linux-kernel - Re: [PATCH v2 02/16] KVM: arm64: Check for PTE valitity when checking for executable/cacheable

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Message-ID: <20211006104129.s5az46tpny2csfge@gator.home>
Date:   Wed, 6 Oct 2021 12:41:29 +0200
From:   Andrew Jones <drjones@...hat.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org, will@...nel.org,
        qperret@...gle.com, dbrazdil@...gle.com,
        Steven Price <steven.price@....com>,
        Fuad Tabba <tabba@...gle.com>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 02/16] KVM: arm64: Check for PTE valitity when
 checking for executable/cacheable


Hi Marc,

sed s/valitity/validity/ <<<"$SUBJECT"

On Mon, Oct 04, 2021 at 06:48:35PM +0100, Marc Zyngier wrote:
> Don't blindly assume that the PTE is valid when checking whether
> it describes an executable or cacheable mapping.
> 
> This makes sure that we don't issue CMOs for invalid mappings.
> 
> Suggested-by: Will Deacon <will@...nel.org>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  arch/arm64/kvm/hyp/pgtable.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index f8ceebe4982e..6bbfd952f0c5 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -638,12 +638,12 @@ static void stage2_put_pte(kvm_pte_t *ptep, struct kvm_s2_mmu *mmu, u64 addr,
>  static bool stage2_pte_cacheable(struct kvm_pgtable *pgt, kvm_pte_t pte)
>  {
>  	u64 memattr = pte & KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR;
> -	return memattr == KVM_S2_MEMATTR(pgt, NORMAL);
> +	return kvm_pte_valid(pte) && memattr == KVM_S2_MEMATTR(pgt, NORMAL);
>  }
>  
>  static bool stage2_pte_executable(kvm_pte_t pte)
>  {
> -	return !(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN);
> +	return kvm_pte_valid(pte) && !(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN);
>  }
>  
>  static bool stage2_leaf_mapping_allowed(u64 addr, u64 end, u32 level,
> @@ -688,8 +688,7 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
>  	/* Perform CMOs before installation of the guest stage-2 PTE */
>  	if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
>  		mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> -						granule);
> -
> +					       granule);
>  	if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
>  		mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
>  
> @@ -1091,7 +1090,7 @@ static int stage2_flush_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
>  	kvm_pte_t pte = *ptep;
>  	kvm_pte_t *pte_follow;
>  
> -	if (!kvm_pte_valid(pte) || !stage2_pte_cacheable(pgt, pte))
> +	if (!stage2_pte_cacheable(pgt, pte))
>  		return 0;
>  
>  	pte_follow = kvm_pte_follow(pte, mm_ops);
> -- 
> 2.30.2
> 

Reviewed-by: Andrew Jones <drjones@...hat.com>