The following commit has been merged into the x86/hyperv branch of tip:
Commit-ID: dce7cd62754b5d4a6e401b8b0769ec94cf971041
Gitweb: https://git.kernel.org/tip/dce7cd62754b5d4a6e401b8b0769ec94cf971041
Author: Andrea Parri <parri.andrea@xxxxxxxxx>
AuthorDate: Thu, 03 Oct 2019 17:52:00 +02:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 12 Nov 2019 11:44:21 +01:00
x86/hyperv: Allow guests to enable InvariantTSC
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@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191003155200.22022-1-parri.andrea@xxxxxxxxx
---
arch/x86/include/asm/hyperv-tlfs.h | 5 +++++
arch/x86/kernel/cpu/mshyperv.c | 7 ++++++-
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 7a27056..887b1d6 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -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.
*/
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 062f772..6f7c822 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -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
- 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
|