[PATCH v14 04/25] x86/kvmclock: Cleanup the code

Pavel Tatashin
2018-07-18T02:21:50Z

From: Thomas Gleixner <tglx@linutronix.de>

- Cleanup the mrs write for wall clock. The type casts to (int) are sloppy
because the wrmsr parameters are u32 and aside of that wrmsrl() already
provides the high/low split for free.

- Remove the pointless get_cpu()/put_cpu() dance from various
functions. Either they are called during early init where CPU is
guaranteed to be 0 or they are already called from non preemptible
context where smp_processor_id() can be used safely

- Simplify the convoluted check for kvmclock in the init function.

- Mark the parameter parsing function __init. No point in keeping it
around.

- Convert to pr_info()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kernel/kvmclock.c | 76 ++++++++++++--------------------------
1 file changed, 23 insertions(+), 53 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index cbf0a6b9217b..04d2f5e1d783 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -37,7 +37,7 @@ static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
static u64 kvm_sched_clock_offset;

-static int parse_no_kvmclock(char *arg)
+static int __init parse_no_kvmclock(char *arg)
{
kvmclock = 0;
return 0;
@@ -61,13 +61,9 @@ static struct pvclock_wall_clock wall_clock;
static void kvm_get_wallclock(struct timespec64 *now)
{
struct pvclock_vcpu_time_info *vcpu_time;
- int low, high;
int cpu;

- low = (int)slow_virt_to_phys(&wall_clock);
- high = ((u64)slow_virt_to_phys(&wall_clock) >> 32);
-
- native_write_msr(msr_kvm_wall_clock, low, high);
+ wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));

cpu = get_cpu();

@@ -117,11 +113,11 @@ static inline void kvm_sched_clock_init(bool stable)
kvm_sched_clock_offset = kvm_clock_read();
pv_time_ops.sched_clock = kvm_sched_clock_read;

- printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
- kvm_sched_clock_offset);
+ pr_info("kvm-clock: using sched offset of %llu cycles",
+ kvm_sched_clock_offset);

BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
- sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
+ sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
}

/*
@@ -135,15 +131,7 @@ static inline void kvm_sched_clock_init(bool stable)
*/
static unsigned long kvm_get_tsc_khz(void)
{
- struct pvclock_vcpu_time_info *src;
- int cpu;
- unsigned long tsc_khz;
-
- cpu = get_cpu();
- src = &hv_clock[cpu].pvti;
- tsc_khz = pvclock_tsc_khz(src);
- put_cpu();
- return tsc_khz;
+ return pvclock_tsc_khz(&hv_clock[0].pvti);
}

static void kvm_get_preset_lpj(void)
@@ -160,29 +148,27 @@ static void kvm_get_preset_lpj(void)

bool kvm_check_and_clear_guest_paused(void)
{
- bool ret = false;
struct pvclock_vcpu_time_info *src;
- int cpu = smp_processor_id();
+ bool ret = false;

if (!hv_clock)
return ret;

- src = &hv_clock[cpu].pvti;
+ src = &hv_clock[smp_processor_id()].pvti;
if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
src->flags &= ~PVCLOCK_GUEST_STOPPED;
pvclock_touch_watchdogs();
ret = true;
}
-
return ret;
}

struct clocksource kvm_clock = {
- .name = "kvm-clock",
- .read = kvm_clock_get_cycles,
- .rating = 400,
- .mask = CLOCKSOURCE_MASK(64),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .name = "kvm-clock",
+ .read = kvm_clock_get_cycles,
+ .rating = 400,
+ .mask = CLOCKSOURCE_MASK(64),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
EXPORT_SYMBOL_GPL(kvm_clock);

@@ -198,7 +184,7 @@ static void kvm_register_clock(char *txt)
src = &hv_clock[cpu].pvti;
pa = slow_virt_to_phys(src) | 0x01ULL;
wrmsrl(msr_kvm_system_time, pa);
- pr_info("kvm-clock: cpu %d, msr %llx, %s\n", cpu, pa, txt);
+ pr_info("kvm-clock: cpu %d, msr %llx, %s", cpu, pa, txt);
}

static void kvm_save_sched_clock_state(void)
@@ -243,20 +229,19 @@ static void kvm_shutdown(void)

void __init kvmclock_init(void)
{
- struct pvclock_vcpu_time_info *vcpu_time;
- int cpu;
u8 flags;

- if (!kvm_para_available())
+ if (!kvm_para_available() || !kvmclock)
return;

- if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
+ if (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)))
+ } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
return;
+ }

- printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
+ pr_info("kvm-clock: Using msrs %x and %x",
msr_kvm_system_time, msr_kvm_wall_clock);

hv_clock = (struct pvclock_vsyscall_time_info *)hv_clock_mem;
@@ -265,20 +250,15 @@ void __init kvmclock_init(void)
if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);

- cpu = get_cpu();
- vcpu_time = &hv_clock[cpu].pvti;
- flags = pvclock_read_flags(vcpu_time);
-
+ flags = pvclock_read_flags(&hv_clock[0].pvti);
kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
- put_cpu();

x86_platform.calibrate_tsc = kvm_get_tsc_khz;
x86_platform.calibrate_cpu = 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.early_percpu_clock_init =
- kvm_setup_secondary_clock;
+ x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
#endif
x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
@@ -294,26 +274,16 @@ void __init kvmclock_init(void)
int __init kvm_setup_vsyscall_timeinfo(void)
{
#ifdef CONFIG_X86_64
- int cpu;
u8 flags;
- struct pvclock_vcpu_time_info *vcpu_time;

if (!hv_clock)
return 0;

- cpu = get_cpu();
-
- vcpu_time = &hv_clock[cpu].pvti;
- flags = pvclock_read_flags(vcpu_time);
-
- if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
- put_cpu();
+ flags = pvclock_read_flags(&hv_clock[0].pvti);
+ if (!(flags & PVCLOCK_TSC_STABLE_BIT))
return 1;
- }

pvclock_set_pvti_cpu0_va(hv_clock);
- put_cpu();
-
kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
#endif
return 0;
--
2.18.0