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

[Andrew Jones]

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@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
>  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@xxxxxxxxxx>