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Date: Wed, 8 Feb 2017 18:07:44 +0100
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: x86@...nel.org, Andy Lutomirski <luto@...capital.net>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
Dexuan Cui <decui@...rosoft.com>, linux-kernel@...r.kernel.org,
devel@...uxdriverproject.org,
virtualization@...ts.linux-foundation.org
Subject: [PATCH RFC 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method
Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol
defined by the hypervisor is different from VCLOCK_PVCLOCK. Implement the
required support re-using pvclock_page VVAR as VCLOCK_PVCLOCK is mutually
exclusive with VCLOCK_HVCLOCK at run time.
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
arch/x86/entry/vdso/vclock_gettime.c | 48 ++++++++++++++++++++++++++++++++++++
arch/x86/entry/vdso/vma.c | 26 +++++++++++++------
arch/x86/hyperv/hv_init.c | 3 +++
arch/x86/include/asm/clocksource.h | 3 ++-
4 files changed, 72 insertions(+), 8 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 9d4d6e1..93e9dcd 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -17,6 +17,7 @@
#include <asm/unistd.h>
#include <asm/msr.h>
#include <asm/pvclock.h>
+#include <asm/mshyperv.h>
#include <linux/math64.h>
#include <linux/time.h>
#include <linux/kernel.h>
@@ -141,6 +142,49 @@ static notrace u64 vread_pvclock(int *mode)
return last;
}
#endif
+#ifdef CONFIG_HYPERV_CLOCK
+/* (a * b) >> 64 implementation */
+static inline u64 mul64x64_hi(u64 a, u64 b)
+{
+ u64 a_lo, a_hi, b_lo, b_hi, p1, p2;
+
+ a_lo = (u32)a;
+ a_hi = a >> 32;
+ b_lo = (u32)b;
+ b_hi = b >> 32;
+ p1 = a_lo * b_hi;
+ p2 = a_hi * b_lo;
+
+ return a_hi * b_hi + (p1 >> 32) + (p2 >> 32) +
+ ((((a_lo * b_lo) >> 32) + (u32)p1 + (u32)p2) >> 32);
+
+}
+
+static notrace u64 vread_hvclock(int *mode)
+{
+ const struct ms_hyperv_tsc_page *tsc_pg =
+ (const struct ms_hyperv_tsc_page *)&pvclock_page;
+ u64 sequence, scale, offset, current_tick, cur_tsc;
+
+ while (1) {
+ sequence = READ_ONCE(tsc_pg->tsc_sequence);
+ if (!sequence)
+ break;
+
+ scale = READ_ONCE(tsc_pg->tsc_scale);
+ offset = READ_ONCE(tsc_pg->tsc_offset);
+ rdtscll(cur_tsc);
+
+ current_tick = mul64x64_hi(cur_tsc, scale) + offset;
+
+ if (READ_ONCE(tsc_pg->tsc_sequence) == sequence)
+ return current_tick;
+ }
+
+ *mode = VCLOCK_NONE;
+ return 0;
+}
+#endif
notrace static u64 vread_tsc(void)
{
@@ -173,6 +217,10 @@ notrace static inline u64 vgetsns(int *mode)
else if (gtod->vclock_mode == VCLOCK_PVCLOCK)
cycles = vread_pvclock(mode);
#endif
+#ifdef CONFIG_HYPERV_CLOCK
+ else if (gtod->vclock_mode == VCLOCK_HVCLOCK)
+ cycles = vread_hvclock(mode);
+#endif
else
return 0;
v = (cycles - gtod->cycle_last) & gtod->mask;
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 10820f6..4b9d90c 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -21,6 +21,7 @@
#include <asm/page.h>
#include <asm/desc.h>
#include <asm/cpufeature.h>
+#include <asm/mshyperv.h>
#if defined(CONFIG_X86_64)
unsigned int __read_mostly vdso64_enabled = 1;
@@ -112,13 +113,24 @@ static int vvar_fault(const struct vm_special_mapping *sm,
ret = vm_insert_pfn(vma, vmf->address,
__pa_symbol(&__vvar_page) >> PAGE_SHIFT);
} else if (sym_offset == image->sym_pvclock_page) {
- struct pvclock_vsyscall_time_info *pvti =
- pvclock_pvti_cpu0_va();
- if (pvti && vclock_was_used(VCLOCK_PVCLOCK)) {
- ret = vm_insert_pfn(
- vma,
- vmf->address,
- __pa(pvti) >> PAGE_SHIFT);
+ if (vclock_was_used(VCLOCK_PVCLOCK)) {
+ struct pvclock_vsyscall_time_info *pvti =
+ pvclock_pvti_cpu0_va();
+ if (pvti) {
+ ret = vm_insert_pfn(
+ vma,
+ vmf->address,
+ __pa(pvti) >> PAGE_SHIFT);
+ }
+ } else if (vclock_was_used(VCLOCK_HVCLOCK)) {
+ struct ms_hyperv_tsc_page *tsc_pg =
+ hv_get_tsc_page();
+ if (tsc_pg) {
+ ret = vm_insert_pfn(
+ vma,
+ vmf->address,
+ vmalloc_to_pfn(tsc_pg));
+ }
}
}
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index aa36049..3d534d2 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -157,6 +157,9 @@ void hyperv_init(void)
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;
}
diff --git a/arch/x86/include/asm/clocksource.h b/arch/x86/include/asm/clocksource.h
index eae33c7..47bea8c 100644
--- a/arch/x86/include/asm/clocksource.h
+++ b/arch/x86/include/asm/clocksource.h
@@ -6,7 +6,8 @@
#define VCLOCK_NONE 0 /* No vDSO clock available. */
#define VCLOCK_TSC 1 /* vDSO should use vread_tsc. */
#define VCLOCK_PVCLOCK 2 /* vDSO should use vread_pvclock. */
-#define VCLOCK_MAX 2
+#define VCLOCK_HVCLOCK 3 /* vDSO should use vread_hvclock. */
+#define VCLOCK_MAX 3
struct arch_clocksource_data {
int vclock_mode;
--
2.9.3
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