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From: Andrew Jones <drjones@redhat.com>
To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Cc: maz@kernel.org, steven.price@arm.com, pbonzini@redhat.com
Subject: [PATCH v2 2/6] KVM: arm64: pvtime: Fix potential loss of stolen time
Date: Tue,  4 Aug 2020 19:06:00 +0200	[thread overview]
Message-ID: <20200804170604.42662-3-drjones@redhat.com> (raw)
In-Reply-To: <20200804170604.42662-1-drjones@redhat.com>

We should only check current->sched_info.run_delay once when
updating stolen time. Otherwise there's a chance there could
be a change between checks that we miss (preemption disabling
comes after vcpu request checks).

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 arch/arm64/kvm/pvtime.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c
index c3ef4ebd6846..95f9580275b1 100644
--- a/arch/arm64/kvm/pvtime.c
+++ b/arch/arm64/kvm/pvtime.c
@@ -13,6 +13,7 @@
 void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = vcpu->kvm;
+	u64 last_steal = vcpu->arch.steal.last_steal;
 	u64 steal;
 	__le64 steal_le;
 	u64 offset;
@@ -24,8 +25,8 @@ void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
 
 	/* Let's do the local bookkeeping */
 	steal = vcpu->arch.steal.steal;
-	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
-	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
+	vcpu->arch.steal.last_steal = READ_ONCE(current->sched_info.run_delay);
+	steal += vcpu->arch.steal.last_steal - last_steal;
 	vcpu->arch.steal.steal = steal;
 
 	steal_le = cpu_to_le64(steal);
-- 
2.25.4


WARNING: multiple messages have this Message-ID (diff)
From: Andrew Jones <drjones@redhat.com>
To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Cc: maz@kernel.org, pbonzini@redhat.com, steven.price@arm.com
Subject: [PATCH v2 2/6] KVM: arm64: pvtime: Fix potential loss of stolen time
Date: Tue,  4 Aug 2020 19:06:00 +0200	[thread overview]
Message-ID: <20200804170604.42662-3-drjones@redhat.com> (raw)
In-Reply-To: <20200804170604.42662-1-drjones@redhat.com>

We should only check current->sched_info.run_delay once when
updating stolen time. Otherwise there's a chance there could
be a change between checks that we miss (preemption disabling
comes after vcpu request checks).

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 arch/arm64/kvm/pvtime.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c
index c3ef4ebd6846..95f9580275b1 100644
--- a/arch/arm64/kvm/pvtime.c
+++ b/arch/arm64/kvm/pvtime.c
@@ -13,6 +13,7 @@
 void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = vcpu->kvm;
+	u64 last_steal = vcpu->arch.steal.last_steal;
 	u64 steal;
 	__le64 steal_le;
 	u64 offset;
@@ -24,8 +25,8 @@ void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
 
 	/* Let's do the local bookkeeping */
 	steal = vcpu->arch.steal.steal;
-	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
-	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
+	vcpu->arch.steal.last_steal = READ_ONCE(current->sched_info.run_delay);
+	steal += vcpu->arch.steal.last_steal - last_steal;
 	vcpu->arch.steal.steal = steal;
 
 	steal_le = cpu_to_le64(steal);
-- 
2.25.4

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kvmarm@lists.cs.columbia.edu
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  parent reply	other threads:[~2020-08-04 17:08 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-04 17:05 [PATCH v2 0/6] KVM: arm64: pvtime: Fixes and a new cap Andrew Jones
2020-08-04 17:05 ` Andrew Jones
2020-08-04 17:05 ` [PATCH v2 1/6] KVM: arm64: pvtime: steal-time is only supported when configured Andrew Jones
2020-08-04 17:05   ` Andrew Jones
2020-08-04 17:06 ` Andrew Jones [this message]
2020-08-04 17:06   ` [PATCH v2 2/6] KVM: arm64: pvtime: Fix potential loss of stolen time Andrew Jones
2020-08-04 17:06 ` [PATCH v2 3/6] KVM: arm64: Drop type input from kvm_put_guest Andrew Jones
2020-08-04 17:06   ` Andrew Jones
2020-08-04 17:06 ` [PATCH v2 4/6] KVM: arm64: pvtime: Fix stolen time accounting across migration Andrew Jones
2020-08-04 17:06   ` Andrew Jones
2020-08-04 17:06 ` [PATCH v2 5/6] KVM: Documentation: Minor fixups Andrew Jones
2020-08-04 17:06   ` Andrew Jones
2020-08-04 17:06 ` [PATCH v2 6/6] arm64/x86: KVM: Introduce steal-time cap Andrew Jones
2020-08-04 17:06   ` Andrew Jones
2020-08-05 15:37 ` [PATCH v2 0/6] KVM: arm64: pvtime: Fixes and a new cap Steven Price
2020-08-05 15:37   ` Steven Price
2020-08-19 12:50 ` Andrew Jones
2020-08-19 12:50   ` Andrew Jones
2020-08-21 13:04   ` Marc Zyngier
2020-08-21 13:04     ` Marc Zyngier

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