We now added a new set of clock-related msrs in replacement of the old ones. In theory, we could just try to use them and get a return value indicating they do not exist, due to our use of kvm_write_msr_save.
However, kvm clock registration happens very early, and if we ever try to write to a non-existant MSR, we raise a lethal #GP, since our idt handlers are not in place yet. So this patch tests for a cpuid feature exported by the host to decide which set of msrs are supported. Signed-off-by: Glauber Costa <[email protected]> --- arch/x86/include/asm/kvm_para.h | 4 ++ arch/x86/kernel/kvmclock.c | 68 +++++++++++++++++++++++++++------------ 2 files changed, 51 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 0cffb96..a32710a 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -16,6 +16,10 @@ #define KVM_FEATURE_CLOCKSOURCE 0 #define KVM_FEATURE_NOP_IO_DELAY 1 #define KVM_FEATURE_MMU_OP 2 +/* We could just try to use new msr values, but they are queried very early, + * kernel does not have idt handlers yet, and failures are fatal */ +#define KVM_FEATURE_CLOCKSOURCE2 3 + #define MSR_KVM_WALL_CLOCK_OLD 0x11 #define MSR_KVM_SYSTEM_TIME_OLD 0x12 diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index feaeb0d..6d814ce 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -29,6 +29,7 @@ #define KVM_SCALE 22 static int kvmclock = 1; +static int kvm_use_new_msrs = 0; static int parse_no_kvmclock(char *arg) { @@ -41,6 +42,18 @@ early_param("no-kvmclock", parse_no_kvmclock); static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); static struct pvclock_wall_clock wall_clock; +static int kvm_system_time_write_value(int low, int high) +{ + if (kvm_use_new_msrs) + return native_write_msr_safe(MSR_KVM_SYSTEM_TIME_OLD, low, high); + else + return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high); +} + +static void kvm_turnoff_clock(void) +{ + kvm_system_time_write_value(0, 0); +} /* * The wallclock is the time of day when we booted. Since then, some time may * have elapsed since the hypervisor wrote the data. So we try to account for @@ -54,7 +67,11 @@ static unsigned long kvm_get_wallclock(void) low = (int)__pa_symbol(&wall_clock); high = ((u64)__pa_symbol(&wall_clock) >> 32); - native_write_msr(MSR_KVM_WALL_CLOCK, low, high); + + if (kvm_use_new_msrs) + native_write_msr_safe(MSR_KVM_WALL_CLOCK, low, high); + else + native_write_msr(MSR_KVM_WALL_CLOCK_OLD, low, high); vcpu_time = &get_cpu_var(hv_clock); pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); @@ -130,7 +147,8 @@ static int kvm_register_clock(char *txt) high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", cpu, high, low, txt); - return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high); + + return kvm_system_time_write_value(low, high); } #ifdef CONFIG_X86_LOCAL_APIC @@ -165,14 +183,14 @@ static void __init kvm_smp_prepare_boot_cpu(void) #ifdef CONFIG_KEXEC static void kvm_crash_shutdown(struct pt_regs *regs) { - native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); + kvm_turnoff_clock(); native_machine_crash_shutdown(regs); } #endif static void kvm_shutdown(void) { - native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); + kvm_turnoff_clock(); native_machine_shutdown(); } @@ -181,27 +199,35 @@ void __init kvmclock_init(void) if (!kvm_para_available()) return; - if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { - if (kvm_register_clock("boot clock")) - return; - pv_time_ops.sched_clock = kvm_clock_read; - x86_platform.calibrate_tsc = kvm_get_tsc_khz; - x86_platform.get_wallclock = kvm_get_wallclock; - x86_platform.set_wallclock = kvm_set_wallclock; + if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) + kvm_use_new_msrs = 1; + else if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) + kvm_use_new_msrs = 0; + else + return; + + printk(KERN_INFO "kvm-clock: %ssing clocksource new msrs", + kvm_use_new_msrs ? "U": "Not u"); + + if (kvm_register_clock("boot clock")) + return; + pv_time_ops.sched_clock = kvm_clock_read; + x86_platform.calibrate_tsc = kvm_get_tsc_khz; + x86_platform.get_wallclock = kvm_get_wallclock; + x86_platform.set_wallclock = kvm_set_wallclock; #ifdef CONFIG_X86_LOCAL_APIC - x86_cpuinit.setup_percpu_clockev = - kvm_setup_secondary_clock; + x86_cpuinit.setup_percpu_clockev = + kvm_setup_secondary_clock; #endif #ifdef CONFIG_SMP - smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; + smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; #endif - machine_ops.shutdown = kvm_shutdown; + machine_ops.shutdown = kvm_shutdown; #ifdef CONFIG_KEXEC - machine_ops.crash_shutdown = kvm_crash_shutdown; + machine_ops.crash_shutdown = kvm_crash_shutdown; #endif - kvm_get_preset_lpj(); - clocksource_register(&kvm_clock); - pv_info.paravirt_enabled = 1; - pv_info.name = "KVM"; - } + kvm_get_preset_lpj(); + clocksource_register(&kvm_clock); + pv_info.paravirt_enabled = 1; + pv_info.name = "KVM"; } -- 1.6.2.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
