[kvm-unit-tests PATCH] x86: vmx: Fix the check whether CMCI is supported

[Nadav Amit <namit@vmware.com>]

The logic of figuring out whether CMCI is supported is broken, causing
the CMCI accessing tests to fail on Skylake bare-metal.

Determine whether CMCI is supported according to the maximum entries in
the LVT as encoded in the APIC version register.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 lib/x86/apic.h  |  7 +++++++
 x86/vmx_tests.c | 10 +---------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/lib/x86/apic.h b/lib/x86/apic.h
index b5bf208..a7eff63 100644
--- a/lib/x86/apic.h
+++ b/lib/x86/apic.h
@@ -70,6 +70,11 @@ static inline u32 x2apic_msr(u32 reg)
 	return APIC_BASE_MSR + (reg >> 4);
 }
 
+static inline bool apic_lvt_entry_supported(int idx)
+{
+	return GET_APIC_MAXLVT(apic_read(APIC_LVR)) >= idx;
+}
+
 static inline bool x2apic_reg_reserved(u32 reg)
 {
 	switch (reg) {
@@ -83,6 +88,8 @@ static inline bool x2apic_reg_reserved(u32 reg)
 	case 0x3a0 ... 0x3d0:
 	case 0x3f0:
 		return true;
+	case APIC_CMCI:
+		return !apic_lvt_entry_supported(6);
 	default:
 		return false;
 	}
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index f4b348b..0c710cd 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -5863,11 +5863,6 @@ static u64 virt_x2apic_mode_nibble1(u64 val)
 	return val & 0xf0;
 }
 
-static bool is_cmci_enabled(void)
-{
-	return rdmsr(MSR_IA32_MCG_CAP) & BIT_ULL(10);
-}
-
 static void virt_x2apic_mode_rd_expectation(
 	u32 reg, bool virt_x2apic_mode_on, bool disable_x2apic,
 	bool apic_register_virtualization, bool virtual_interrupt_delivery,
@@ -5877,9 +5872,6 @@ static void virt_x2apic_mode_rd_expectation(
 		!x2apic_reg_reserved(reg) &&
 		reg != APIC_EOI;
 
-	if (reg == APIC_CMCI && !is_cmci_enabled())
-		readable = false;
-
 	expectation->rd_exit_reason = VMX_VMCALL;
 	expectation->virt_fn = virt_x2apic_mode_identity;
 	if (virt_x2apic_mode_on && apic_register_virtualization) {
@@ -5943,7 +5935,7 @@ static bool get_x2apic_wr_val(u32 reg, u64 *val)
 		*val = apic_read(reg);
 		break;
 	case APIC_CMCI:
-		if (!is_cmci_enabled())
+		if (!apic_lvt_entry_supported(6))
 			return false;
 		*val = apic_read(reg);
 		break;
-- 
2.17.1