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From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Cc: James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>, Will Deacon <will@kernel.org>,
	Ricardo Koller <ricarkol@google.com>
Subject: [PATCH v3 5/5] KVM: arm64: vhe: Drop extra isb() on guest exit
Date: Thu, 13 Apr 2023 09:14:41 +0100	[thread overview]
Message-ID: <20230413081441.165134-6-maz@kernel.org> (raw)
In-Reply-To: <20230413081441.165134-1-maz@kernel.org>

__kvm_vcpu_run_vhe() end on VHE with an isb(). However, this
function is only reachable via kvm_call_hyp_ret(), which already
contains an isb() in order to mimick the behaviour of nVHE and
provide a context synchronisation event.

We thus have two isb()s back to back, which is one too many.
Drop the first one and solely rely on the one in the helper.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/vhe/switch.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index cd3f3117bf16..3d868e84c7a0 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -227,11 +227,10 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	/*
 	 * When we exit from the guest we change a number of CPU configuration
-	 * parameters, such as traps.  Make sure these changes take effect
-	 * before running the host or additional guests.
+	 * parameters, such as traps.  We rely on the isb() in kvm_call_hyp*()
+	 * to make sure these changes take effect before running the host or
+	 * additional guests.
 	 */
-	isb();
-
 	return ret;
 }
 
-- 
2.34.1


WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Cc: James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>, Will Deacon <will@kernel.org>,
	Ricardo Koller <ricarkol@google.com>
Subject: [PATCH v3 5/5] KVM: arm64: vhe: Drop extra isb() on guest exit
Date: Thu, 13 Apr 2023 09:14:41 +0100	[thread overview]
Message-ID: <20230413081441.165134-6-maz@kernel.org> (raw)
In-Reply-To: <20230413081441.165134-1-maz@kernel.org>

__kvm_vcpu_run_vhe() end on VHE with an isb(). However, this
function is only reachable via kvm_call_hyp_ret(), which already
contains an isb() in order to mimick the behaviour of nVHE and
provide a context synchronisation event.

We thus have two isb()s back to back, which is one too many.
Drop the first one and solely rely on the one in the helper.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/vhe/switch.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index cd3f3117bf16..3d868e84c7a0 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -227,11 +227,10 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	/*
 	 * When we exit from the guest we change a number of CPU configuration
-	 * parameters, such as traps.  Make sure these changes take effect
-	 * before running the host or additional guests.
+	 * parameters, such as traps.  We rely on the isb() in kvm_call_hyp*()
+	 * to make sure these changes take effect before running the host or
+	 * additional guests.
 	 */
-	isb();
-
 	return ret;
 }
 
-- 
2.34.1


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2023-04-13  8:14 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-13  8:14 [PATCH v3 0/5] KVM: arm64: Synchronise speculative page table walks on translation regime change Marc Zyngier
2023-04-13  8:14 ` Marc Zyngier
2023-04-13  8:14 ` [PATCH v3 1/5] KVM: arm64: nvhe: Synchronise with page table walker on vcpu run Marc Zyngier
2023-04-13  8:14   ` Marc Zyngier
2023-04-13  8:14 ` [PATCH v3 2/5] KVM: arm64: nvhe: Synchronise with page table walker on TLBI Marc Zyngier
2023-04-13  8:14   ` Marc Zyngier
2023-04-13 15:53   ` Oliver Upton
2023-04-13 15:53     ` Oliver Upton
2023-04-14  7:24     ` Marc Zyngier
2023-04-14  7:24       ` Marc Zyngier
2023-04-13  8:14 ` [PATCH v3 3/5] KVM: arm64: pkvm: Document the side effects of kvm_flush_dcache_to_poc() Marc Zyngier
2023-04-13  8:14   ` Marc Zyngier
2023-04-13  8:14 ` [PATCH v3 4/5] KVM: arm64: vhe: Synchronise with page table walker on MMU update Marc Zyngier
2023-04-13  8:14   ` Marc Zyngier
2023-04-13  8:14 ` Marc Zyngier [this message]
2023-04-13  8:14   ` [PATCH v3 5/5] KVM: arm64: vhe: Drop extra isb() on guest exit Marc Zyngier

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