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Commit 838815a7 authored by Glauber Costa's avatar Glauber Costa Committed by Avi Kivity
Browse files

x86: KVM guest: Try using new kvm clock msrs 



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: default avatarGlauber Costa <glommer@redhat.com>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 84478c82

arch/x86/kernel/kvmclock.c

+32 −21
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 
#define KVM_SCALE 22



static int kvmclock = 1;

static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;

static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;



static int parse_no_kvmclock(char *arg)

{
@@ -54,7 +56,8 @@ 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);



	native_write_msr(msr_kvm_wall_clock, low, high);



	vcpu_time = &get_cpu_var(hv_clock);

	pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
@@ -130,7 +133,8 @@ 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 native_write_msr_safe(msr_kvm_system_time, low, high);

}



#ifdef CONFIG_X86_LOCAL_APIC
@@ -165,14 +169,14 @@ 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);

	native_write_msr(msr_kvm_system_time, 0, 0);

	native_machine_crash_shutdown(regs);

}

#endif



static void kvm_shutdown(void)

{

	native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);

	native_write_msr(msr_kvm_system_time, 0, 0);

	native_machine_shutdown();

}
@@ -181,7 +185,15 @@ void __init kvmclock_init(void) 
	if (!kvm_para_available())

		return;



	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {

	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {

		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;

		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;

	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))

		return;



	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",

		msr_kvm_system_time, msr_kvm_wall_clock);



	if (kvm_register_clock("boot clock"))

		return;

	pv_time_ops.sched_clock = kvm_clock_read;
@@ -204,4 +216,3 @@ void __init kvmclock_init(void) 
	pv_info.paravirt_enabled = 1;

	pv_info.name = "KVM";

}
 
}