[PATCH v4 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

From: Michael Kelley
Date: Fri Jun 28 2019 - 14:34:15 EST

Continue consolidating Hyper-V clock and timer code into an ISA
independent Hyper-V clocksource driver. Move the existing clocksource
code under drivers/hv and arch/x86 to the new clocksource driver
while separating out the ISA dependencies. Update Hyper-V
initialization to call initialization and cleanup routines since the
Hyper-V synthetic clock is not independently enumerated in ACPI.
Update Hyper-V clocksource users in KVM and VDSO to get definitions
from a new include file.

No behavior is changed and no new functionality is added.

Suggested-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
arch/x86/entry/vdso/vma.c | 2 +-
arch/x86/hyperv/hv_init.c | 91 +---------------------
arch/x86/include/asm/mshyperv.h | 81 +++----------------
arch/x86/include/asm/vdso/gettimeofday.h | 2 +-
arch/x86/kvm/x86.c | 1 +
drivers/clocksource/hyperv_timer.c | 130 +++++++++++++++++++++++++++++++
include/clocksource/hyperv_timer.h | 78 +++++++++++++++++++
7 files changed, 225 insertions(+), 160 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 8db1f59..349a61d 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -22,7 +22,7 @@
#include <asm/page.h>
#include <asm/desc.h>
#include <asm/cpufeature.h>
-#include <asm/mshyperv.h>
+#include <clocksource/hyperv_timer.h>

#if defined(CONFIG_X86_64)
unsigned int __read_mostly vdso64_enabled = 1;
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 1608050..0e033ef 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -17,64 +17,13 @@
#include <linux/version.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
-#include <linux/clockchips.h>
#include <linux/hyperv.h>
#include <linux/slab.h>
#include <linux/cpuhotplug.h>
-
-#ifdef CONFIG_HYPERV_TSCPAGE
-
-static struct ms_hyperv_tsc_page *tsc_pg;
-
-struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
-{
- return tsc_pg;
-}
-EXPORT_SYMBOL_GPL(hv_get_tsc_page);
-
-static u64 read_hv_clock_tsc(struct clocksource *arg)
-{
- u64 current_tick = hv_read_tsc_page(tsc_pg);
-
- if (current_tick == U64_MAX)
- 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,
-};
+#include <clocksource/hyperv_timer.h>

void *hv_hypercall_pg;
EXPORT_SYMBOL_GPL(hv_hypercall_pg);
-struct clocksource *hyperv_cs;
-EXPORT_SYMBOL_GPL(hyperv_cs);

u32 *hv_vp_index;
EXPORT_SYMBOL_GPL(hv_vp_index);
@@ -343,42 +292,8 @@ void __init hyperv_init(void)

x86_init.pci.arch_init = hv_pci_init;

- /*
- * Register Hyper-V specific clocksource.
- */
-#ifdef CONFIG_HYPERV_TSCPAGE
- if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
- union hv_x64_msr_hypercall_contents tsc_msr;
-
- tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
- if (!tsc_pg)
- goto register_msr_cs;
-
- hyperv_cs = &hyperv_cs_tsc;
-
- 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);
-
- hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK;
-
- clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
- return;
- }
-register_msr_cs:
-#endif
- /*
- * For 32 bit guests just use the MSR based mechanism for reading
- * the partition counter.
- */
-
- hyperv_cs = &hyperv_cs_msr;
- if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE)
- clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
-
+ /* Register Hyper-V specific clocksource */
+ hv_init_clocksource();
return;

remove_cpuhp_state:
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index cc60e61..f4fa8a9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -105,6 +105,17 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
#define hv_get_crash_ctl(val) \
rdmsrl(HV_X64_MSR_CRASH_CTL, val)

+#define hv_get_time_ref_count(val) \
+ rdmsrl(HV_X64_MSR_TIME_REF_COUNT, val)
+
+#define hv_get_reference_tsc(val) \
+ rdmsrl(HV_X64_MSR_REFERENCE_TSC, val)
+#define hv_set_reference_tsc(val) \
+ wrmsrl(HV_X64_MSR_REFERENCE_TSC, val)
+#define hv_set_clocksource_vdso(val) \
+ ((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
+#define hv_get_raw_timer() rdtsc_ordered()
+
void hyperv_callback_vector(void);
void hyperv_reenlightenment_vector(void);
#ifdef CONFIG_TRACING
@@ -133,7 +144,6 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}


#if IS_ENABLED(CONFIG_HYPERV)
-extern struct clocksource *hyperv_cs;
extern void *hv_hypercall_pg;
extern void __percpu **hyperv_pcpu_input_arg;

@@ -387,73 +397,4 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
}
#endif /* CONFIG_HYPERV */

-#ifdef CONFIG_HYPERV_TSCPAGE
-struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
-static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
- u64 *cur_tsc)
-{
- u64 scale, offset;
- u32 sequence;
-
- /*
- * The protocol for reading Hyper-V TSC page is specified in Hypervisor
- * Top-Level Functional Specification ver. 3.0 and above. To get the
- * reference time we must do the following:
- * - READ ReferenceTscSequence
- * A special '0' value indicates the time source is unreliable and we
- * need to use something else. The currently published specification
- * versions (up to 4.0b) contain a mistake and wrongly claim '-1'
- * instead of '0' as the special value, see commit c35b82ef0294.
- * - ReferenceTime =
- * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
- * - READ ReferenceTscSequence again. In case its value has changed
- * since our first reading we need to discard ReferenceTime and repeat
- * the whole sequence as the hypervisor was updating the page in
- * between.
- */
- do {
- sequence = READ_ONCE(tsc_pg->tsc_sequence);
- if (!sequence)
- return U64_MAX;
- /*
- * Make sure we read sequence before we read other values from
- * TSC page.
- */
- smp_rmb();
-
- scale = READ_ONCE(tsc_pg->tsc_scale);
- offset = READ_ONCE(tsc_pg->tsc_offset);
- *cur_tsc = rdtsc_ordered();
-
- /*
- * Make sure we read sequence after we read all other values
- * from TSC page.
- */
- smp_rmb();
-
- } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
-
- return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
-}
-
-static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
-{
- u64 cur_tsc;
-
- return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
-}
-
-#else
-static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
-{
- return NULL;
-}
-
-static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
- u64 *cur_tsc)
-{
- BUG();
- return U64_MAX;
-}
-#endif
#endif
diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index a14039a..ae91429 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -18,7 +18,7 @@
#include <asm/unistd.h>
#include <asm/msr.h>
#include <asm/pvclock.h>
-#include <asm/mshyperv.h>
+#include <clocksource/hyperv_timer.h>

#define __vdso_data (VVAR(_vdso_data))

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9857992..07ddb1e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -67,6 +67,7 @@
#include <asm/mshyperv.h>
#include <asm/hypervisor.h>
#include <asm/intel_pt.h>
+#include <clocksource/hyperv_timer.h>

#define CREATE_TRACE_POINTS
#include "trace.h"
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 30615f3..274614d 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -14,6 +14,8 @@
#include <linux/percpu.h>
#include <linux/cpumask.h>
#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
#include <linux/mm.h>
#include <clocksource/hyperv_timer.h>
#include <asm/hyperv-tlfs.h>
@@ -189,3 +191,131 @@ void hv_stimer_global_cleanup(void)
hv_stimer_free();
}
EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
+
+/*
+ * Code and definitions for the Hyper-V clocksources. Two
+ * clocksources are defined: one that reads the Hyper-V defined MSR, and
+ * the other that uses the TSC reference page feature as defined in the
+ * TLFS. The MSR version is for compatibility with old versions of
+ * Hyper-V and 32-bit x86. The TSC reference page version is preferred.
+ */
+
+struct clocksource *hyperv_cs;
+EXPORT_SYMBOL_GPL(hyperv_cs);
+
+#ifdef CONFIG_HYPERV_TSCPAGE
+
+static struct ms_hyperv_tsc_page *tsc_pg;
+
+struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+ return tsc_pg;
+}
+EXPORT_SYMBOL_GPL(hv_get_tsc_page);
+
+static u64 read_hv_sched_clock_tsc(void)
+{
+ u64 current_tick = hv_read_tsc_page(tsc_pg);
+
+ if (current_tick == U64_MAX)
+ hv_get_time_ref_count(current_tick);
+
+ return current_tick;
+}
+
+static u64 read_hv_clock_tsc(struct clocksource *arg)
+{
+ return read_hv_sched_clock_tsc();
+}
+
+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_sched_clock_msr(void)
+{
+ 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.
+ */
+ hv_get_time_ref_count(current_tick);
+ return current_tick;
+}
+
+static u64 read_hv_clock_msr(struct clocksource *arg)
+{
+ return read_hv_sched_clock_msr();
+}
+
+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,
+};
+
+void __init hv_init_clocksource(void)
+{
+#ifdef CONFIG_HYPERV_TSCPAGE
+ if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
+
+ u64 tsc_msr;
+ phys_addr_t phys_addr;
+
+ tsc_pg = vmalloc(PAGE_SIZE);
+ if (!tsc_pg)
+ goto register_msr_cs;
+
+ hyperv_cs = &hyperv_cs_tsc;
+ phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
+
+ /* The Hyper-V TLFS specifies to preserve the value of
+ * reserved bits in registers. So read the existing
+ * value, preserve the low order 12 bits, and add in
+ * the guest physical address (which already has at
+ * least the low 12 bits set to zero since it is page
+ * aligned). Also set the "enable" bit, which is bit 0.
+ */
+ hv_get_reference_tsc(tsc_msr);
+ tsc_msr &= GENMASK_ULL(11, 0);
+ tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
+ hv_set_reference_tsc(tsc_msr);
+
+ hv_set_clocksource_vdso(hyperv_cs_tsc);
+ clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
+
+ /*
+ * sched_clock_register is needed on ARM64 but
+ * is a no-op on x86
+ */
+ sched_clock_register(read_hv_sched_clock_tsc,
+ 64, HV_CLOCK_HZ);
+ return;
+ }
+register_msr_cs:
+#endif
+ /*
+ * For 32 bit guests just use the MSR based mechanism for reading
+ * the partition counter.
+ */
+ hyperv_cs = &hyperv_cs_msr;
+ if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) {
+ clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
+
+ /*
+ * sched_clock_register is needed on ARM64 but
+ * is a no-op on x86
+ */
+ sched_clock_register(read_hv_sched_clock_msr,
+ 64, HV_CLOCK_HZ);
+ }
+}
+EXPORT_SYMBOL_GPL(hv_init_clocksource);
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index ba5dc17..e17e8a2 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -13,6 +13,10 @@
#ifndef __CLKSOURCE_HYPERV_TIMER_H
#define __CLKSOURCE_HYPERV_TIMER_H

+#include <linux/clocksource.h>
+#include <linux/math64.h>
+#include <asm/mshyperv.h>
+
#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
#define HV_MIN_DELTA_TICKS 1

@@ -24,4 +28,78 @@
extern void hv_stimer_global_cleanup(void);
extern void hv_stimer0_isr(void);

+#if IS_ENABLED(CONFIG_HYPERV)
+extern struct clocksource *hyperv_cs;
+extern void hv_init_clocksource(void);
+#endif /* CONFIG_HYPERV */
+
+#ifdef CONFIG_HYPERV_TSCPAGE
+extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+ u64 *cur_tsc)
+{
+ u64 scale, offset;
+ u32 sequence;
+
+ /*
+ * The protocol for reading Hyper-V TSC page is specified in Hypervisor
+ * Top-Level Functional Specification ver. 3.0 and above. To get the
+ * reference time we must do the following:
+ * - READ ReferenceTscSequence
+ * A special '0' value indicates the time source is unreliable and we
+ * need to use something else. The currently published specification
+ * versions (up to 4.0b) contain a mistake and wrongly claim '-1'
+ * instead of '0' as the special value, see commit c35b82ef0294.
+ * - ReferenceTime =
+ * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
+ * - READ ReferenceTscSequence again. In case its value has changed
+ * since our first reading we need to discard ReferenceTime and repeat
+ * the whole sequence as the hypervisor was updating the page in
+ * between.
+ */
+ do {
+ sequence = READ_ONCE(tsc_pg->tsc_sequence);
+ if (!sequence)
+ return U64_MAX;
+ /*
+ * Make sure we read sequence before we read other values from
+ * TSC page.
+ */
+ smp_rmb();
+
+ scale = READ_ONCE(tsc_pg->tsc_scale);
+ offset = READ_ONCE(tsc_pg->tsc_offset);
+ *cur_tsc = hv_get_raw_timer();
+
+ /*
+ * Make sure we read sequence after we read all other values
+ * from TSC page.
+ */
+ smp_rmb();
+
+ } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
+
+ return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
+}
+
+static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
+{
+ u64 cur_tsc;
+
+ return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
+}
+
+#else /* CONFIG_HYPERV_TSC_PAGE */
+static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+ return NULL;
+}
+
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+ u64 *cur_tsc)
+{
+ return U64_MAX;
+}
+#endif /* CONFIG_HYPERV_TSCPAGE */
+
#endif
--
1.8.3.1