[PATCH 4/4] KVM: VMX: Support TSC scaling with enlightened VMCS

[Vitaly Kuznetsov]

Enlightened VMCS v1 now includes the required field for TSC scaling
feature so SECONDARY_EXEC_TSC_SCALING doesn't need to be filtered out
for KVM on Hyper-V case. Hyper-V on KVM is, however, trickier: to not
break live migration to older KVMs which may not support the feature
it needs to stay filtered out. Eventually, a new KVM capability indicating
support for the new fields will need to be introduced.

While on it, update the comment why VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL/
VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL are kept filtered out and add
missing spaces in trace_kvm_nested_vmenter_failed() strings making the
output ugly.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/kvm/vmx/evmcs.c |  8 +++++++-
 arch/x86/kvm/vmx/evmcs.h | 11 ++++-------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 61a702a804f8..6ed4bb2e676e 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -385,7 +385,13 @@ void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata)
 		ctl_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
 		break;
 	case MSR_IA32_VMX_PROCBASED_CTLS2:
-		ctl_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC;
+		/*
+		 * Initially, SECONDARY_EXEC_TSC_SCALING was filtered out as there was no
+		 * TscMultiplier field defined in eVMCS. Keep the status quo to not break
+		 * live migration.
+		 */
+		ctl_high &= ~(EVMCS1_UNSUPPORTED_2NDEXEC |
+			      SECONDARY_EXEC_TSC_SCALING);
 		break;
 	case MSR_IA32_VMX_TRUE_PINBASED_CTLS:
 	case MSR_IA32_VMX_PINBASED_CTLS:
diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index 8d70f9aea94b..5fd9292be6bb 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -37,16 +37,14 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
  *	EPTP_LIST_ADDRESS               = 0x00002024,
  *	VMREAD_BITMAP                   = 0x00002026,
  *	VMWRITE_BITMAP                  = 0x00002028,
- *
- *	TSC_MULTIPLIER                  = 0x00002032,
  *	PLE_GAP                         = 0x00004020,
  *	PLE_WINDOW                      = 0x00004022,
  *	VMX_PREEMPTION_TIMER_VALUE      = 0x0000482E,
- *      GUEST_IA32_PERF_GLOBAL_CTRL     = 0x00002808,
- *      HOST_IA32_PERF_GLOBAL_CTRL      = 0x00002c04,
  *
- * Currently unsupported in KVM:
- *	GUEST_IA32_RTIT_CTL		= 0x00002814,
+ *	While GUEST_IA32_PERF_GLOBAL_CTRL and HOST_IA32_PERF_GLOBAL_CTRL
+ *	are present in eVMCSv1, Windows 11 still has issues booting when
+ *	VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL/VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL
+ *	are exposed to it, keep them filtered out.
  */
 #define EVMCS1_UNSUPPORTED_PINCTRL (PIN_BASED_POSTED_INTR | \
 				    PIN_BASED_VMX_PREEMPTION_TIMER)
@@ -57,7 +55,6 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
 	 SECONDARY_EXEC_ENABLE_PML |					\
 	 SECONDARY_EXEC_ENABLE_VMFUNC |					\
 	 SECONDARY_EXEC_SHADOW_VMCS |					\
-	 SECONDARY_EXEC_TSC_SCALING |					\
 	 SECONDARY_EXEC_PAUSE_LOOP_EXITING)
 #define EVMCS1_UNSUPPORTED_VMEXIT_CTRL					\
 	(VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL |				\
-- 
2.35.3


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