From 2dbd780e34ac53e79c6c359ce12b89ed665ef562 Mon Sep 17 00:00:00 2001
From: Andrew Jones <drjones@redhat.com>
Date: Tue, 4 Aug 2020 19:06:00 +0200
Subject: [PATCH] KVM: arm64: pvtime: Fix potential loss of stolen time
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>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200804170604.42662-3-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 c3ef4ebd68465b..95f9580275b1b5 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);
--
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