KVM: x86: workaround SuSE's 2.6.16 pvclock vs masterclock issue (54750f2c) · Commits · 戴 / test

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 <mtosatti@redhat.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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 {

arch/x86/kvm/x86.c

+14 −1

Original line number	Diff line number	Diff line
		@@ -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);

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