Commit-ID: 71c2a2d0a81f096a2932fccb39a500116fece554 Gitweb: http://git.kernel.org/tip/71c2a2d0a81f096a2932fccb39a500116fece554 Author: Vitaly Kuznetsov <[email protected]> AuthorDate: Thu, 22 Jun 2017 18:07:30 +0800 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 22 Jun 2017 15:35:12 +0200
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 <[email protected]> Signed-off-by: Vitaly Kuznetsov <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: Stephen Hemminger <[email protected]> Cc: Haiyang Zhang <[email protected]> Cc: Jork Loeser <[email protected]> Cc: [email protected] Cc: "K. Y. Srinivasan" <[email protected]> Link: http://lkml.kernel.org/r/[email protected] --- arch/x86/kernel/cpu/mshyperv.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 3563c8e..70e717f 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) {
