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x86/hyperv: Allow guests to enable InvariantTSC

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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
This commit is contained in:
Andrea Parri 2019-10-03 17:52:00 +02:00 committed by Thomas Gleixner
parent b264f57fde
commit dce7cd6275
2 changed files with 11 additions and 1 deletions
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5
arch/x86/include/asm/hyperv-tlfs.h
View file

@ -86,6 +86,8 @@
#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
@ -270,6 +272,9 @@
#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.
*/

5
arch/x86/kernel/cpu/mshyperv.c
View file

@ -285,7 +285,12 @@ static void __init ms_hyperv_init_platform(void)
machine_ops.shutdown = hv_machine_shutdown;
machine_ops.crash_shutdown = hv_machine_crash_shutdown;
#endif
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