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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2015-01-20 15:54:52 -0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-01-20 20:38:39 +0100 |
| commit | 54750f2cf042c42b4223d67b1bd20138464bde0e (patch) | |
| tree | e7914883c6452ee68f2b8f7e583db12d2afbe955 /arch/x86/kvm/x86.c | |
| parent | 69b0049a89ad418cd68aa59e7f1e6619a04a4a6f (diff) | |
| download | lwn-54750f2cf042c42b4223d67b1bd20138464bde0e.tar.gz lwn-54750f2cf042c42b4223d67b1bd20138464bde0e.zip | |
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 <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 15 |
1 files changed, 14 insertions, 1 deletions
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); |