kvm: kvmclock: use get_cpu() and put_cpu()

We can use get_cpu() and put_cpu() to replace
preempt_disable()/cpu = smp_processor_id() and
preempt_enable() for slightly better code.

Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d9156ceecdff03ca0d55ab2834df0d4f7e828203..0bf3467d7f30fb75cd1433ea79f3786bead85694 100644 (file)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -59,13 +59,12 @@ static void kvm_get_wallclock(struct timespec *now)
 
        native_write_msr(msr_kvm_wall_clock, low, high);
 
-       preempt_disable();
-       cpu = smp_processor_id();
+       cpu = get_cpu();
 
        vcpu_time = &hv_clock[cpu].pvti;
        pvclock_read_wallclock(&wall_clock, vcpu_time, now);
 
-       preempt_enable();
+       put_cpu();
 }
 
 static int kvm_set_wallclock(const struct timespec *now)
@@ -107,11 +106,10 @@ static unsigned long kvm_get_tsc_khz(void)
        int cpu;
        unsigned long tsc_khz;
 
-       preempt_disable();
-       cpu = smp_processor_id();
+       cpu = get_cpu();
        src = &hv_clock[cpu].pvti;
        tsc_khz = pvclock_tsc_khz(src);
-       preempt_enable();
+       put_cpu();
        return tsc_khz;
 }
 
@@ -284,23 +282,22 @@ int __init kvm_setup_vsyscall_timeinfo(void)
 
        size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
 
-       preempt_disable();
-       cpu = smp_processor_id();
+       cpu = get_cpu();
 
        vcpu_time = &hv_clock[cpu].pvti;
        flags = pvclock_read_flags(vcpu_time);
 
        if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
-               preempt_enable();
+               put_cpu();
                return 1;
        }
 
        if ((ret = pvclock_init_vsyscall(hv_clock, size))) {
-               preempt_enable();
+               put_cpu();
                return ret;
        }
 
-       preempt_enable();
+       put_cpu();
 
        kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
 #endif