Drivers: hv: vmbus: Consolidate all Hyper-V specific clocksource code

As part of the effort to separate out architecture specific code,
consolidate all Hyper-V specific clocksource code to an architecture
specific code.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 117 insertions, 23 deletions

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index b5c8e04deacb..860233af4568 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -24,6 +24,79 @@
 #include <linux/version.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
+#include <linux/clockchips.h>
+
+
+#ifdef CONFIG_X86_64
+
+static struct ms_hyperv_tsc_page *tsc_pg;
+
+static u64 read_hv_clock_tsc(struct clocksource *arg)
+{
+	u64 current_tick;
+
+	if (tsc_pg->tsc_sequence != 0) {
+		/*
+		 * Use the tsc page to compute the value.
+		 */
+
+		while (1) {
+			u64 tmp;
+			u32 sequence = tsc_pg->tsc_sequence;
+			u64 cur_tsc;
+			u64 scale = tsc_pg->tsc_scale;
+			s64 offset = tsc_pg->tsc_offset;
+
+			rdtscll(cur_tsc);
+			/* current_tick = ((cur_tsc *scale) >> 64) + offset */
+			asm("mulq %3"
+				: "=d" (current_tick), "=a" (tmp)
+				: "a" (cur_tsc), "r" (scale));
+
+			current_tick += offset;
+			if (tsc_pg->tsc_sequence == sequence)
+				return current_tick;
+
+			if (tsc_pg->tsc_sequence != 0)
+				continue;
+			/*
+			 * Fallback using MSR method.
+			 */
+			break;
+		}
+	}
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+	return current_tick;
+}
+
+static struct clocksource hyperv_cs_tsc = {
+		.name		= "hyperv_clocksource_tsc_page",
+		.rating		= 400,
+		.read		= read_hv_clock_tsc,
+		.mask		= CLOCKSOURCE_MASK(64),
+		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+#endif
+
+static u64 read_hv_clock_msr(struct clocksource *arg)
+{
+	u64 current_tick;
+	/*
+	 * Read the partition counter to get the current tick count. This count
+	 * is set to 0 when the partition is created and is incremented in
+	 * 100 nanosecond units.
+	 */
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+	return current_tick;
+}
+
+static struct clocksource hyperv_cs_msr = {
+	.name		= "hyperv_clocksource_msr",
+	.rating		= 400,
+	.read		= read_hv_clock_msr,
+	.mask		= CLOCKSOURCE_MASK(64),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
 
 static void *hypercall_pg;
 /*
@@ -31,6 +104,7 @@ static void *hypercall_pg;
  * hypervisor has been detected.
  *
  * 1. Setup the hypercall page.
+ * 2. Register Hyper-V specific clocksource.
  */
 void hyperv_init(void)
 {
@@ -58,6 +132,37 @@ void hyperv_init(void)
 	hypercall_msr.enable = 1;
 	hypercall_msr.guest_physical_address = vmalloc_to_pfn(hypercall_pg);
 	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	/*
+	 * Register Hyper-V specific clocksource.
+	 */
+#ifdef CONFIG_X86_64
+	if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
+		union hv_x64_msr_hypercall_contents tsc_msr;
+
+		tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
+		if (!tsc_pg) {
+			clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
+			return;
+		}
+
+		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
+
+		tsc_msr.enable = 1;
+		tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);
+
+		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
+		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
+		return;
+	}
+#endif
+	/*
+	 * For 32 bit guests just use the MSR based mechanism for reading
+	 * the partition counter.
+	 */
+
+	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
+		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
 }
 
 /*
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index ed8e07399071..adfe8cc9f7e3 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -26,6 +26,18 @@ union hv_x64_msr_hypercall_contents {
 };
 
 /*
+ * TSC page layout.
+ */
+
+struct ms_hyperv_tsc_page {
+	volatile u32 tsc_sequence;
+	u32 reserved1;
+	volatile u64 tsc_scale;
+	volatile s64 tsc_offset;
+	u64 reserved2[509];
+};
+
+/*
  * The guest OS needs to register the guest ID with the hypervisor.
  * The guest ID is a 64 bit entity and the structure of this ID is
  * specified in the Hyper-V specification:
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index c5a1e9ba9ae0..d3705a44971c 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -133,26 +133,6 @@ static uint32_t  __init ms_hyperv_platform(void)
 	return 0;
 }
 
-static u64 read_hv_clock(struct clocksource *arg)
-{
-	u64 current_tick;
-	/*
-	 * Read the partition counter to get the current tick count. This count
-	 * is set to 0 when the partition is created and is incremented in
-	 * 100 nanosecond units.
-	 */
-	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-	return current_tick;
-}
-
-static struct clocksource hyperv_cs = {
-	.name		= "hyperv_clocksource",
-	.rating		= 400, /* use this when running on Hyperv*/
-	.read		= read_hv_clock,
-	.mask		= CLOCKSOURCE_MASK(64),
-	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
 static unsigned char hv_get_nmi_reason(void)
 {
 	return 0;
@@ -208,9 +188,6 @@ static void __init ms_hyperv_init_platform(void)
 			     "hv_nmi_unknown");
 #endif
 
-	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
-		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
-
 #ifdef CONFIG_X86_IO_APIC
 	no_timer_check = 1;
 #endif