From: Andrew Jones Date: Tue, 4 Aug 2020 17:06:00 +0000 (+0200) Subject: KVM: arm64: pvtime: Fix potential loss of stolen time X-Git-Tag: v5.9-rc5~6^2~16^2~7 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2dbd780e34ac53e79c6c359ce12b89ed665ef562;p=thirdparty%2Fkernel%2Flinux.git 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 Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20200804170604.42662-3-drjones@redhat.com --- diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c index c3ef4ebd68465..95f9580275b1b 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);