From: Glauber Costa <glommer@redhat.com>
Date: Tue, 11 Aug 2009 13:32:00 -0400
Subject: [x86] kvm: import pvclock.c and headers
Message-id: 1250011926-31633-2-git-send-email-glommer@redhat.com
O-Subject: [PATCH v2 1/7] Import pvclock.c and headers from upstream kernel
Bugzilla: 476075
RH-Acked-by: Juan Quintela <quintela@redhat.com>

This is a copy of upstream version of pvclock.c and its headers. The only
small difference is the use of rtdscll() instead of native_read_tsc, which we lack,
in function pvclock_get_nsec_offset().

I'm putting it in a separate patch, to easy reviewing for you people.

Signed-off-by: Glauber Costa <glommer@redhat.com>

diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 5bf397a..1410349 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -40,6 +40,9 @@ obj-$(CONFIG_VM86)		+= vm86.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
 obj-$(CONFIG_K8_NB)		+= k8.o
+ifndef CONFIG_XEN
+obj-y				+= pvclock.o
+endif
 
 EXTRA_AFLAGS   := -traditional
 
diff --git a/arch/i386/kernel/pvclock.c b/arch/i386/kernel/pvclock.c
new file mode 100644
index 0000000..3b08ff5
--- /dev/null
+++ b/arch/i386/kernel/pvclock.c
@@ -0,0 +1,155 @@
+/*  paravirtual clock -- common code used by kvm/xen
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include <linux/kernel.h>
+#include <linux/percpu.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
+
+	return product;
+}
+
+static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
+{
+	u64 delta;
+	rdtscll(delta);
+	delta -= 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;
+}
+
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
+{
+	u64 pv_tsc_khz = 1000000ULL << 32;
+
+	do_div(pv_tsc_khz, src->tsc_to_system_mul);
+	if (src->tsc_shift < 0)
+		pv_tsc_khz <<= -src->tsc_shift;
+	else
+		pv_tsc_khz >>= src->tsc_shift;
+	return pv_tsc_khz;
+}
+
+cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+{
+	struct pvclock_shadow_time shadow;
+	unsigned version;
+	cycle_t ret, offset;
+
+	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);
+
+	return ret;
+}
+
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
+			    struct pvclock_vcpu_time_info *vcpu_time,
+			    struct timespec *ts)
+{
+	u32 version;
+	u64 delta;
+	struct timespec now;
+
+	/* get wallclock at system boot */
+	do {
+		version = wall_clock->version;
+		rmb();		/* fetch version before time */
+		now.tv_sec  = wall_clock->sec;
+		now.tv_nsec = wall_clock->nsec;
+		rmb();		/* fetch time before checking version */
+	} while ((wall_clock->version & 1) || (version != wall_clock->version));
+
+	delta = pvclock_clocksource_read(vcpu_time);	/* time since system boot */
+	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
+
+	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
+	now.tv_sec = delta;
+
+	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
+}
diff --git a/arch/x86_64/kernel/Makefile b/arch/x86_64/kernel/Makefile
index 9782a3f..023aa49 100644
--- a/arch/x86_64/kernel/Makefile
+++ b/arch/x86_64/kernel/Makefile
@@ -51,6 +51,7 @@ obj-y				+= addon_cpuid_features.o
 ifndef CONFIG_XEN
 obj-y				+= vmware.o
 obj-y				+= hypervisor.o
+obj-y				+= pvclock.o
 endif
 
 CFLAGS_vsyscall.o		:= $(PROFILING) -g0
@@ -63,6 +64,7 @@ microcode-$(subst m,y,$(CONFIG_MICROCODE))  += ../../i386/kernel/microcode.o
 intel_cacheinfo-y		+= ../../i386/kernel/cpu/intel_cacheinfo.o
 addon_cpuid_features-y		+= ../../i386/kernel/cpu/addon_cpuid_features.o
 vmware-y			+= ../../i386/kernel/cpu/vmware.o
+pvclock-y			+= ../../i386/kernel/pvclock.o
 hypervisor-y			+= ../../i386/kernel/cpu/hypervisor.o
 quirks-y			+= ../../i386/kernel/quirks.o
 i8237-y				+= ../../i386/kernel/i8237.o
diff --git a/include/asm-i386/pvclock.h b/include/asm-i386/pvclock.h
new file mode 100644
index 0000000..53235fd
--- /dev/null
+++ b/include/asm-i386/pvclock.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_X86_PVCLOCK_H
+#define _ASM_X86_PVCLOCK_H
+
+#include <linux/clocksource.h>
+#include <asm/pvclock-abi.h>
+
+/* some helper functions for xen and kvm pv clock sources */
+cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
+			    struct pvclock_vcpu_time_info *vcpu,
+			    struct timespec *ts);
+
+#endif /* _ASM_X86_PVCLOCK_H */
diff --git a/include/asm-x86_64/pvclock.h b/include/asm-x86_64/pvclock.h
new file mode 100644
index 0000000..53235fd
--- /dev/null
+++ b/include/asm-x86_64/pvclock.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_X86_PVCLOCK_H
+#define _ASM_X86_PVCLOCK_H
+
+#include <linux/clocksource.h>
+#include <asm/pvclock-abi.h>
+
+/* some helper functions for xen and kvm pv clock sources */
+cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
+			    struct pvclock_vcpu_time_info *vcpu,
+			    struct timespec *ts);
+
+#endif /* _ASM_X86_PVCLOCK_H */