If the hardware supports TSC scaling, Hyper-V will set bit 15 of the
HV_PARTITION_PRIVILEGE_MASK in guest VMs with a compatible Hyper-V
configuration version. Bit 15 corresponds to the
AccessTscInvariantControls privilege. If this privilege bit is set,
guests can access the HvSyntheticInvariantTscControl MSR: guests can
set bit 0 of this synthetic MSR to enable the InvariantTSC feature.
After setting the synthetic MSR, CPUID will enumerate support for
InvariantTSC.
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lkml.kernel.org/r/20191003155200.22022-1-parri.andrea@gmail.com
#define HV_X64_ACCESS_FREQUENCY_MSRS BIT(11)
/* AccessReenlightenmentControls privilege */
#define HV_X64_ACCESS_REENLIGHTENMENT BIT(13)
+/* AccessTscInvariantControls privilege */
+#define HV_X64_ACCESS_TSC_INVARIANT BIT(15)
/*
* Feature identification: indicates which flags were specified at partition
#define HV_X64_MSR_TSC_EMULATION_CONTROL 0x40000107
#define HV_X64_MSR_TSC_EMULATION_STATUS 0x40000108
+/* TSC invariant control */
+#define HV_X64_MSR_TSC_INVARIANT_CONTROL 0x40000118
+
/*
* Declare the MSR used to setup pages used to communicate with the hypervisor.
*/
machine_ops.shutdown = hv_machine_shutdown;
machine_ops.crash_shutdown = hv_machine_crash_shutdown;
#endif
- mark_tsc_unstable("running on Hyper-V");
+ if (ms_hyperv.features & HV_X64_ACCESS_TSC_INVARIANT) {
+ wrmsrl(HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x1);
+ setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
+ } else {
+ mark_tsc_unstable("running on Hyper-V");
+ }
/*
* Generation 2 instances don't support reading the NMI status from