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From: Ricardo Koller <ricarkol@google.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm@lists.linux.dev, Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/4] KVM: arm64: Handle access faults behind the read lock
Date: Tue, 29 Nov 2022 13:00:44 -0800	[thread overview]
Message-ID: <Y4Zy/MtIgeLyRGy9@google.com> (raw)
In-Reply-To: <20221129191946.1735662-4-oliver.upton@linux.dev>

On Tue, Nov 29, 2022 at 07:19:45PM +0000, Oliver Upton wrote:
> As the underlying software walkers are able to traverse and update
> stage-2 in parallel there is no need to serialize access faults.
> 
> Only take the read lock when handling an access fault.
> 
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
>  arch/arm64/kvm/hyp/pgtable.c | 2 +-
>  arch/arm64/kvm/mmu.c         | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 9626f615d9b8..1a3dd9774707 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -1097,7 +1097,7 @@ kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
>  	int ret;
>  
>  	ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
> -				       &pte, NULL, 0);
> +				       &pte, NULL, KVM_PGTABLE_WALK_SHARED);
>  	if (!ret)
>  		dsb(ishst);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 886ad5ee767a..347985a56414 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1404,10 +1404,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
>  
>  	trace_kvm_access_fault(fault_ipa);
>  
> -	write_lock(&vcpu->kvm->mmu_lock);
> +	read_lock(&vcpu->kvm->mmu_lock);
>  	mmu = vcpu->arch.hw_mmu;
>  	pte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
> -	write_unlock(&vcpu->kvm->mmu_lock);
> +	read_unlock(&vcpu->kvm->mmu_lock);
>  
>  	if (kvm_pte_valid(pte))
>  		kvm_set_pfn_accessed(kvm_pte_to_pfn(pte));
> -- 
> 2.38.1.584.g0f3c55d4c2-goog
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Reviewed-by: Ricardo Koller <ricarkol@google.com>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Ricardo Koller <ricarkol@google.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: arm64: Handle access faults behind the read lock
Date: Tue, 29 Nov 2022 13:00:44 -0800	[thread overview]
Message-ID: <Y4Zy/MtIgeLyRGy9@google.com> (raw)
Message-ID: <20221129210044.7Gqgekk3yCx-CT0kQvPq18EH6qhutbCL3Xz4m8nAzBk@z> (raw)
In-Reply-To: <20221129191946.1735662-4-oliver.upton@linux.dev>

On Tue, Nov 29, 2022 at 07:19:45PM +0000, Oliver Upton wrote:
> As the underlying software walkers are able to traverse and update
> stage-2 in parallel there is no need to serialize access faults.
> 
> Only take the read lock when handling an access fault.
> 
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
>  arch/arm64/kvm/hyp/pgtable.c | 2 +-
>  arch/arm64/kvm/mmu.c         | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 9626f615d9b8..1a3dd9774707 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -1097,7 +1097,7 @@ kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
>  	int ret;
>  
>  	ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
> -				       &pte, NULL, 0);
> +				       &pte, NULL, KVM_PGTABLE_WALK_SHARED);
>  	if (!ret)
>  		dsb(ishst);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 886ad5ee767a..347985a56414 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1404,10 +1404,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
>  
>  	trace_kvm_access_fault(fault_ipa);
>  
> -	write_lock(&vcpu->kvm->mmu_lock);
> +	read_lock(&vcpu->kvm->mmu_lock);
>  	mmu = vcpu->arch.hw_mmu;
>  	pte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
> -	write_unlock(&vcpu->kvm->mmu_lock);
> +	read_unlock(&vcpu->kvm->mmu_lock);
>  
>  	if (kvm_pte_valid(pte))
>  		kvm_set_pfn_accessed(kvm_pte_to_pfn(pte));
> -- 
> 2.38.1.584.g0f3c55d4c2-goog
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Reviewed-by: Ricardo Koller <ricarkol@google.com>

WARNING: multiple messages have this Message-ID (diff)
From: Ricardo Koller <ricarkol@google.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: arm64: Handle access faults behind the read lock
Date: Tue, 29 Nov 2022 13:00:44 -0800	[thread overview]
Message-ID: <Y4Zy/MtIgeLyRGy9@google.com> (raw)
In-Reply-To: <20221129191946.1735662-4-oliver.upton@linux.dev>

On Tue, Nov 29, 2022 at 07:19:45PM +0000, Oliver Upton wrote:
> As the underlying software walkers are able to traverse and update
> stage-2 in parallel there is no need to serialize access faults.
> 
> Only take the read lock when handling an access fault.
> 
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
>  arch/arm64/kvm/hyp/pgtable.c | 2 +-
>  arch/arm64/kvm/mmu.c         | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 9626f615d9b8..1a3dd9774707 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -1097,7 +1097,7 @@ kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
>  	int ret;
>  
>  	ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
> -				       &pte, NULL, 0);
> +				       &pte, NULL, KVM_PGTABLE_WALK_SHARED);
>  	if (!ret)
>  		dsb(ishst);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 886ad5ee767a..347985a56414 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1404,10 +1404,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
>  
>  	trace_kvm_access_fault(fault_ipa);
>  
> -	write_lock(&vcpu->kvm->mmu_lock);
> +	read_lock(&vcpu->kvm->mmu_lock);
>  	mmu = vcpu->arch.hw_mmu;
>  	pte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
> -	write_unlock(&vcpu->kvm->mmu_lock);
> +	read_unlock(&vcpu->kvm->mmu_lock);
>  
>  	if (kvm_pte_valid(pte))
>  		kvm_set_pfn_accessed(kvm_pte_to_pfn(pte));
> -- 
> 2.38.1.584.g0f3c55d4c2-goog
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Reviewed-by: Ricardo Koller <ricarkol@google.com>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-11-29 21:00 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-29 19:19 [PATCH 0/4] KVM: arm64: Parallel access faults Oliver Upton
2022-11-29 19:19 ` Oliver Upton
2022-11-29 19:19 ` Oliver Upton
2022-11-29 19:19 ` [PATCH 1/4] KVM: arm64: Use KVM's pte type/helpers in handle_access_fault() Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 19:19 ` [PATCH 2/4] KVM: arm64: Don't serialize if the access flag isn't set Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 20:52   ` Ricardo Koller
2022-11-29 20:52     ` Ricardo Koller
2022-11-29 20:52     ` Ricardo Koller
2022-11-29 21:15     ` Oliver Upton
2022-11-29 21:15       ` Oliver Upton
2022-11-29 21:15       ` Oliver Upton
2022-11-30  1:23       ` Ricardo Koller
2022-11-30  1:23         ` Ricardo Koller
2022-11-30  1:23         ` Ricardo Koller
2022-11-30  8:21         ` Marc Zyngier
2022-11-30  8:21           ` Marc Zyngier
2022-11-30  8:21           ` Marc Zyngier
2022-11-30 23:21           ` Ricardo Koller
2022-11-30 23:21             ` Ricardo Koller
2022-11-30 23:21             ` Ricardo Koller
2022-12-01 18:11       ` Oliver Upton
2022-12-01 18:11         ` Oliver Upton
2022-12-01 18:11         ` Oliver Upton
2022-11-29 19:19 ` [PATCH 3/4] KVM: arm64: Handle access faults behind the read lock Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 21:00   ` Ricardo Koller [this message]
2022-11-29 21:00     ` Ricardo Koller
2022-11-29 21:00     ` Ricardo Koller
2022-11-29 19:19 ` [PATCH 4/4] KVM: arm64: Condition HW AF updates on config option Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-29 19:19   ` Oliver Upton
2022-11-30 16:54 ` [PATCH 0/4] KVM: arm64: Parallel access faults Marc Zyngier
2022-11-30 16:54   ` Marc Zyngier
2022-11-30 16:54   ` Marc Zyngier

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