From 54750f2cf042c42b4223d67b1bd20138464bde0e Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Tue, 20 Jan 2015 15:54:52 -0200 Subject: [PATCH] KVM: x86: workaround SuSE's 2.6.16 pvclock vs masterclock issue SuSE's 2.6.16 kernel fails to boot if the delta between tsc_timestamp and rdtsc is larger than a given threshold: * If we get more than the below threshold into the future, we rerequest * the real time from the host again which has only little offset then * that we need to adjust using the TSC. * * For now that threshold is 1/5th of a jiffie. That should be good * enough accuracy for completely broken systems, but also give us swing * to not call out to the host all the time. */ #define PVCLOCK_DELTA_MAX ((1000000000ULL / HZ) / 5) Disable masterclock support (which increases said delta) in case the boot vcpu does not use MSR_KVM_SYSTEM_TIME_NEW. Upstreams kernels which support pvclock vsyscalls (and therefore make use of PVCLOCK_STABLE_BIT) use MSR_KVM_SYSTEM_TIME_NEW. Signed-off-by: Marcelo Tosatti Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/x86.c | 15 ++++++++++++++- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 97a5dd0222c8..177b2f2ff9fb 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -627,6 +627,8 @@ struct kvm_arch { #ifdef CONFIG_KVM_MMU_AUDIT int audit_point; #endif + + bool boot_vcpu_runs_old_kvmclock; }; struct kvm_vm_stat { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index dcb996bfafa4..917672f8034a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1542,7 +1542,8 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm) &ka->master_cycle_now); ka->use_master_clock = host_tsc_clocksource && vcpus_matched - && !backwards_tsc_observed; + && !backwards_tsc_observed + && !ka->boot_vcpu_runs_old_kvmclock; if (ka->use_master_clock) atomic_set(&kvm_guest_has_master_clock, 1); @@ -2174,8 +2175,20 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_KVM_SYSTEM_TIME_NEW: case MSR_KVM_SYSTEM_TIME: { u64 gpa_offset; + struct kvm_arch *ka = &vcpu->kvm->arch; + kvmclock_reset(vcpu); + if (vcpu->vcpu_id == 0 && !msr_info->host_initiated) { + bool tmp = (msr == MSR_KVM_SYSTEM_TIME); + + if (ka->boot_vcpu_runs_old_kvmclock != tmp) + set_bit(KVM_REQ_MASTERCLOCK_UPDATE, + &vcpu->requests); + + ka->boot_vcpu_runs_old_kvmclock = tmp; + } + vcpu->arch.time = data; kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu); -- 2.20.1