diff options
| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2017-06-22 12:07:30 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2017-06-22 15:35:12 +0200 |
| commit | 71c2a2d0a81f096a2932fccb39a500116fece554 (patch) | |
| tree | 0d633df9e9084d3f46b1cfea517c3f36165a6eca /arch | |
| parent | x86/hyperv: Check frequency MSRs presence according to the specification (diff) | |
| download | linux-71c2a2d0a81f096a2932fccb39a500116fece554.tar.xz linux-71c2a2d0a81f096a2932fccb39a500116fece554.zip | |
x86/hyperv: Read TSC frequency from a synthetic MSR
It was found that SMI_TRESHOLD of 50000 is not enough for Hyper-V
guests in nested environment and falling back to counting jiffies
is not an option for Gen2 guests as they don't have PIT. As Hyper-V
provides TSC frequency in a synthetic MSR we can just use this information
instead of doing a error prone calibration.
Reported-and-tested-by: Ladi Prosek <lprosek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jork Loeser <jloeser@microsoft.com>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Link: http://lkml.kernel.org/r/20170622100730.18112-3-vkuznets@redhat.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/mshyperv.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 3563c8e6c014..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; @@ -193,6 +202,12 @@ 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_ACCESS_FREQUENCY_MSRS && ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { |