Linus,
Please pull the latest x86-hyperv-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
x86-hyperv-for-linus
# HEAD: 71c2a2d0a81f096a2932fccb39a500116fece554 x86/hyperv: Read TSC
frequency from a synthetic MSR
Avoid boot time TSC calibration on Hyper-V hosts, to improve calibration
robustness. (Vitaly Kuznetsov)
Thanks,
Ingo
------------------>
Vitaly Kuznetsov (2):
x86/hyperv: Check frequency MSRs presence according to the specification
x86/hyperv: Read TSC frequency from a synthetic MSR
arch/x86/include/uapi/asm/hyperv.h | 15 ++++++---------
arch/x86/kernel/cpu/mshyperv.c | 18 +++++++++++++++++-
2 files changed, 23 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/uapi/asm/hyperv.h
b/arch/x86/include/uapi/asm/hyperv.h
index 432df4b1baec..f4fef5a24ebd 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -34,16 +34,10 @@
#define HV_X64_MSR_REFERENCE_TSC 0x40000021
/*
- * There is a single feature flag that signifies the presence of the MSR
- * that can be used to retrieve both the local APIC Timer frequency as
- * well as the TSC frequency.
+ * There is a single feature flag that signifies if the partition has access
+ * to MSRs with local APIC and TSC frequencies.
*/
-
-/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
-#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1 << 11)
-
-/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
-#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1 << 11)
+#define HV_X64_ACCESS_FREQUENCY_MSRS (1 << 11)
/*
* Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
@@ -73,6 +67,9 @@
*/
#define HV_X64_MSR_STAT_PAGES_AVAILABLE (1 << 8)
+/* Frequency MSRs available */
+#define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE (1 << 8)
+
/* Crash MSR available */
#define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE (1 << 10)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 04cb8d34ccb8..70e717fccdd6 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -161,6 +161,15 @@ static int hv_nmi_unknown(unsigned int val, struct pt_regs
*regs)
}
#endif
+static unsigned long hv_get_tsc_khz(void)
+{
+ unsigned long freq;
+
+ rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
+
+ return freq / 1000;
+}
+
static void __init ms_hyperv_init_platform(void)
{
int hv_host_info_eax;
@@ -193,8 +202,15 @@ static void __init ms_hyperv_init_platform(void)
hv_host_info_edx >> 24, hv_host_info_edx & 0xFFFFFF);
}
+ if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
+ ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
+ x86_platform.calibrate_tsc = hv_get_tsc_khz;
+ x86_platform.calibrate_cpu = hv_get_tsc_khz;
+ }
+
#ifdef CONFIG_X86_LOCAL_APIC
- if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
+ if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
+ ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
/*
* Get the APIC frequency.
*/
