1 files changed, 95 insertions, 82 deletions

diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 03801f2f761..2f355d229a5 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -17,84 +17,18 @@
 
 #include <linux/kernel.h>
 #include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+#include <linux/gfp.h>
+#include <linux/bootmem.h>
+#include <asm/fixmap.h>
 #include <asm/pvclock.h>
 
-/*
- * These are perodically updated
- *    xen: magic shared_info page
- *    kvm: gpa registered via msr
- * and then copied here.
- */
-struct pvclock_shadow_time {
-	u64 tsc_timestamp;     /* TSC at last update of time vals.  */
-	u64 system_timestamp;  /* Time, in nanosecs, since boot.    */
-	u32 tsc_to_nsec_mul;
-	int tsc_shift;
-	u32 version;
-};
-
-/*
- * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
- * yielding a 64-bit result.
- */
-static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
-{
-	u64 product;
-#ifdef __i386__
-	u32 tmp1, tmp2;
-#endif
-
-	if (shift < 0)
-		delta >>= -shift;
-	else
-		delta <<= shift;
-
-#ifdef __i386__
-	__asm__ (
-		"mul  %5       ; "
-		"mov  %4,%%eax ; "
-		"mov  %%edx,%4 ; "
-		"mul  %5       ; "
-		"xor  %5,%5    ; "
-		"add  %4,%%eax ; "
-		"adc  %5,%%edx ; "
-		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
-		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
-#elif defined(__x86_64__)
-	__asm__ (
-		"mul %%rdx ; shrd $32,%%rdx,%%rax"
-		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
-#else
-#error implement me!
-#endif
+static u8 valid_flags __read_mostly = 0;
 
-	return product;
-}
-
-static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
+void pvclock_set_flags(u8 flags)
 {
-	u64 delta = native_read_tsc() - shadow->tsc_timestamp;
-	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
-}
-
-/*
- * Reads a consistent set of time-base values from hypervisor,
- * into a shadow data area.
- */
-static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
-					struct pvclock_vcpu_time_info *src)
-{
-	do {
-		dst->version = src->version;
-		rmb();		/* fetch version before data */
-		dst->tsc_timestamp     = src->tsc_timestamp;
-		dst->system_timestamp  = src->system_time;
-		dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;
-		dst->tsc_shift         = src->tsc_shift;
-		rmb();		/* test version after fetching data */
-	} while ((src->version & 1) || (dst->version != src->version));
-
-	return dst->version;
+	valid_flags = flags;
 }
 
 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
@@ -109,19 +43,74 @@ unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
 	return pv_tsc_khz;
 }
 
+void pvclock_touch_watchdogs(void)
+{
+	touch_softlockup_watchdog_sync();
+	clocksource_touch_watchdog();
+	rcu_cpu_stall_reset();
+	reset_hung_task_detector();
+}
+
+static atomic64_t last_value = ATOMIC64_INIT(0);
+
+void pvclock_resume(void)
+{
+	atomic64_set(&last_value, 0);
+}
+
+u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
+{
+	unsigned version;
+	cycle_t ret;
+	u8 flags;
+
+	do {
+		version = __pvclock_read_cycles(src, &ret, &flags);
+	} while ((src->version & 1) || version != src->version);
+
+	return flags & valid_flags;
+}
+
 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
 {
-	struct pvclock_shadow_time shadow;
 	unsigned version;
-	cycle_t ret, offset;
+	cycle_t ret;
+	u64 last;
+	u8 flags;
 
 	do {
-		version = pvclock_get_time_values(&shadow, src);
-		barrier();
-		offset = pvclock_get_nsec_offset(&shadow);
-		ret = shadow.system_timestamp + offset;
-		barrier();
-	} while (version != src->version);
+		version = __pvclock_read_cycles(src, &ret, &flags);
+	} while ((src->version & 1) || version != src->version);
+
+	if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
+		src->flags &= ~PVCLOCK_GUEST_STOPPED;
+		pvclock_touch_watchdogs();
+	}
+
+	if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
+		(flags & PVCLOCK_TSC_STABLE_BIT))
+		return ret;
+
+	/*
+	 * Assumption here is that last_value, a global accumulator, always goes
+	 * forward. If we are less than that, we should not be much smaller.
+	 * We assume there is an error marging we're inside, and then the correction
+	 * does not sacrifice accuracy.
+	 *
+	 * For reads: global may have changed between test and return,
+	 * but this means someone else updated poked the clock at a later time.
+	 * We just need to make sure we are not seeing a backwards event.
+	 *
+	 * For updates: last_value = ret is not enough, since two vcpus could be
+	 * updating at the same time, and one of them could be slightly behind,
+	 * making the assumption that last_value always go forward fail to hold.
+	 */
+	last = atomic64_read(&last_value);
+	do {
+		if (ret < last)
+			return last;
+		last = atomic64_cmpxchg(&last_value, last, ret);
+	} while (unlikely(last != ret));
 
 	return ret;
 }
@@ -151,3 +140,27 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
 
 	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
 }
+
+#ifdef CONFIG_X86_64
+/*
+ * Initialize the generic pvclock vsyscall state.  This will allocate
+ * a/some page(s) for the per-vcpu pvclock information, set up a
+ * fixmap mapping for the page(s)
+ */
+
+int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
+				 int size)
+{
+	int idx;
+
+	WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
+
+	for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
+		__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
+			     __pa(i) + (idx*PAGE_SIZE),
+			     PAGE_KERNEL_VVAR);
+	}
+
+	return 0;
+}
+#endif