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KVM: arm64: pvtime: Fix potential loss of stolen time

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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
This commit is contained in:
Andrew Jones 2020-08-04 19:06:00 +02:00 committed by Marc Zyngier
parent 38480df564
commit 2dbd780e34
1 changed files with 3 additions and 2 deletions
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5
arch/arm64/kvm/pvtime.c
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@ -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);