linux-kernel - [PATCH] KVM: x86: Add Intel CPUID.1F cpuid emulation support

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Date:   Mon, 22 Apr 2019 14:40:34 +0800
From:   Like Xu <like.xu@...ux.intel.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Len Brown <lenb@...nel.org>,
        linux-kernel@...r.kernel.org, like.xu@...ux.intel.com
Subject: [PATCH] KVM: x86: Add Intel CPUID.1F cpuid emulation support

Expose Intel V2 Extended Topology Enumeration Leaf to guest only when
host system has multiple software-visible die within each package.

Signed-off-by: Like Xu <like.xu@...ux.intel.com>
---
 arch/x86/kvm/cpuid.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index fd39516..9fc14f2 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -65,6 +65,16 @@ u64 kvm_supported_xcr0(void)
 	return xcr0;
 }
 
+/* We need to check if the host cpu has multi-chip packaging technology. */
+static bool kvm_supported_intel_mcp(void)
+{
+	u32 eax, ignored;
+
+	cpuid_count(0x1f, 0, &eax, &ignored, &ignored, &ignored);
+
+	return boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && (eax != 0);
+}
+
 #define F(x) bit(X86_FEATURE_##x)
 
 int kvm_update_cpuid(struct kvm_vcpu *vcpu)
@@ -426,6 +436,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 	switch (function) {
 	case 0:
 		entry->eax = min(entry->eax, (u32)(f_intel_pt ? 0x14 : 0xd));
+		entry->eax = kvm_supported_intel_mcp() ? 0x1f : entry->eax;
 		break;
 	case 1:
 		entry->edx &= kvm_cpuid_1_edx_x86_features;
@@ -544,6 +555,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		entry->edx = edx.full;
 		break;
 	}
+	/* function 0x1f has additional index. */
+	case 0x1f:
 	/* function 0xb has additional index. */
 	case 0xb: {
 		int i, level_type;
-- 
1.8.3.1