From b33ac88b4c23330043acad930517282eb486db1d Mon Sep 17 00:00:00 2001 From: Kevin Pedretti Date: Sun, 21 Oct 2007 08:54:53 +0200 Subject: [PATCH] KVM: Fix local apic timer divide by zero kvm_lapic_reset() was initializing apic->timer.divide_count to 0, which could potentially lead to a divide by zero error in apic_get_tmcct(). Any guest that reads the APIC's CCR (current count) register before setting DCR (divide configuration) would trigger a divide by zero exception in the host kernel, leading to a host-OS crash. This patch results in apic->timer.divide_count being initialized to 2 at reset, eliminating the bug (DCR=0 at reset, meaning divide by 2). Signed-off-by: Kevin Pedretti Signed-off-by: Avi Kivity --- drivers/kvm/lapic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c index a190587cf6a5..443730e689e3 100644 --- a/drivers/kvm/lapic.c +++ b/drivers/kvm/lapic.c @@ -853,7 +853,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu) apic_set_reg(apic, APIC_ISR + 0x10 * i, 0); apic_set_reg(apic, APIC_TMR + 0x10 * i, 0); } - apic->timer.divide_count = 0; + update_divide_count(apic); atomic_set(&apic->timer.pending, 0); if (vcpu->vcpu_id == 0) vcpu->apic_base |= MSR_IA32_APICBASE_BSP; -- 2.20.1