Re: [PATCH] KVM: arm64: Pass level hint to TLBI during stage-2 permission fault

[Gavin Shan <gshan@xxxxxxxxxx>]

On 9/30/20 11:18 PM, Will Deacon wrote:
> Alex pointed out that we don't pass a level hint to the TLBI instruction
> when handling a stage-2 permission fault, even though the walker does
> at some point have the level information in its hands.
>
> Rework stage2_update_leaf_attrs() so that it can optionally return the
> level of the updated pte to its caller, which can in turn be used to
> provide the correct TLBI level hint.
>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/595cc73e-636e-8b3a-f93a-b4e9fb218db8@xxxxxxx
> Reported-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> ---
>   arch/arm64/kvm/hyp/pgtable.c | 23 ++++++++++++++++-------
>   1 file changed, 16 insertions(+), 7 deletions(-)

Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>

> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 603d6b415337..0cdf6e461cbd 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -694,6 +694,7 @@ struct stage2_attr_data {
>   	kvm_pte_t	attr_set;
>   	kvm_pte_t	attr_clr;
>   	kvm_pte_t	pte;
> +	u32		level;
>   };
>   
>   static int stage2_attr_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
> @@ -706,6 +707,7 @@ static int stage2_attr_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
>   	if (!kvm_pte_valid(pte))
>   		return 0;
>   
> +	data->level = level;
>   	data->pte = pte;
>   	pte &= ~data->attr_clr;
>   	pte |= data->attr_set;
> @@ -723,7 +725,8 @@ static int stage2_attr_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
>   
>   static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr,
>   				    u64 size, kvm_pte_t attr_set,
> -				    kvm_pte_t attr_clr, kvm_pte_t *orig_pte)
> +				    kvm_pte_t attr_clr, kvm_pte_t *orig_pte,
> +				    u32 *level)
>   {
>   	int ret;
>   	kvm_pte_t attr_mask = KVM_PTE_LEAF_ATTR_LO | KVM_PTE_LEAF_ATTR_HI;
> @@ -743,20 +746,24 @@ static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr,
>   
>   	if (orig_pte)
>   		*orig_pte = data.pte;
> +
> +	if (level)
> +		*level = data.level;
>   	return 0;
>   }
>   
>   int kvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size)
>   {
>   	return stage2_update_leaf_attrs(pgt, addr, size, 0,
> -					KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W, NULL);
> +					KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
> +					NULL, NULL);
>   }
>   
>   kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
>   {
>   	kvm_pte_t pte = 0;
>   	stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
> -				 &pte);
> +				 &pte, NULL);
>   	dsb(ishst);
>   	return pte;
>   }
> @@ -765,7 +772,7 @@ kvm_pte_t kvm_pgtable_stage2_mkold(struct kvm_pgtable *pgt, u64 addr)
>   {
>   	kvm_pte_t pte = 0;
>   	stage2_update_leaf_attrs(pgt, addr, 1, 0, KVM_PTE_LEAF_ATTR_LO_S2_AF,
> -				 &pte);
> +				 &pte, NULL);
>   	/*
>   	 * "But where's the TLBI?!", you scream.
>   	 * "Over in the core code", I sigh.
> @@ -778,7 +785,7 @@ kvm_pte_t kvm_pgtable_stage2_mkold(struct kvm_pgtable *pgt, u64 addr)
>   bool kvm_pgtable_stage2_is_young(struct kvm_pgtable *pgt, u64 addr)
>   {
>   	kvm_pte_t pte = 0;
> -	stage2_update_leaf_attrs(pgt, addr, 1, 0, 0, &pte);
> +	stage2_update_leaf_attrs(pgt, addr, 1, 0, 0, &pte, NULL);
>   	return pte & KVM_PTE_LEAF_ATTR_LO_S2_AF;
>   }
>   
> @@ -786,6 +793,7 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
>   				   enum kvm_pgtable_prot prot)
>   {
>   	int ret;
> +	u32 level;
>   	kvm_pte_t set = 0, clr = 0;
>   
>   	if (prot & KVM_PGTABLE_PROT_R)
> @@ -797,8 +805,9 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
>   	if (prot & KVM_PGTABLE_PROT_X)
>   		clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
>   
> -	ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL);
> -	kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, pgt->mmu, addr, 0);
> +	ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL, &level);
> +	if (!ret)
> +		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, pgt->mmu, addr, level);
>   	return ret;
>   }
>   

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