On Wed, May 24, 2017 at 05:07:24PM +0300, Denis Plotnikov wrote: > Do an update of system_time_msr address every time before reading > the value of tsc_timestamp from guest's kvmclock page. > > It should be done in a forcible manner because there is a situation > when system_time_msr has been set by kvm but qemu doesn't aware of it. > This leads to updates of kvmclock_offset without respect of guest's > kvmclock values. > > The situation appears when L2 linux guest runs over L1 linux guest and > the action inducing system_time_msr update is tpr access reporting. > Some L1 linux guests turn off processing TPR access and when L0 > gets an L2 exit induced by TPR MSR access it doesn't enter L1 and > processed it by itself. > Thus, L1 kvm doesn't know about that TPR access happening and doesn't > exit to qemu which in turn doesn't set system_time_msr address. > > This patch fixes this by making sure it knows the correct address every > time it is needed. > > Signed-off-by: Denis Plotnikov <dplotni...@virtuozzo.com> > --- > hw/i386/kvm/clock.c | 32 +++++++++++++++++++++++++++++++- > 1 file changed, 31 insertions(+), 1 deletion(-) > > diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c > index e713162..035196a 100644 > --- a/hw/i386/kvm/clock.c > +++ b/hw/i386/kvm/clock.c > @@ -48,11 +48,38 @@ struct pvclock_vcpu_time_info { > uint8_t pad[2]; > } __attribute__((__packed__)); /* 32 bytes */ > > +static void update_all_system_time_msr(void) > +{ > + CPUState *cpu; > + CPUX86State *env; > + struct { > + struct kvm_msrs info; > + struct kvm_msr_entry entries[1]; > + } msr_data; > + int ret; > + > + msr_data.info.nmsrs = 1; > + msr_data.entries[0].index = MSR_KVM_SYSTEM_TIME; > + > + CPU_FOREACH(cpu) { > + ret = kvm_vcpu_ioctl(cpu, KVM_GET_MSRS, &msr_data); > + > + if (ret < 0) { > + fprintf(stderr, "KVM_GET_MSRS failed: %s\n", strerror(ret)); > + abort(); > + } > + > + assert(ret == 1); > + env = cpu->env_ptr; > + env->system_time_msr = msr_data.entries[0].data; > + } > +} > + > static uint64_t kvmclock_current_nsec(KVMClockState *s) > { > CPUState *cpu = first_cpu; > CPUX86State *env = cpu->env_ptr; > - hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL; > + hwaddr kvmclock_struct_pa; > uint64_t migration_tsc = env->tsc; > struct pvclock_vcpu_time_info time; > uint64_t delta; > @@ -60,6 +87,9 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s) > uint64_t nsec_hi; > uint64_t nsec; > > + update_all_system_time_msr();
I'd rather just cpu_synchronize_state(cpu) here. > + kvmclock_struct_pa = env->system_time_msr & ~1ULL; > + > if (!(env->system_time_msr & 1ULL)) { > /* KVM clock not active */ > return 0; Roman.