linux-kernel - [PATCH] kvm: x86: emulate MSR_PLATFORM

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Message-Id: <1692588151-33716-1-git-send-email-hao.xiang@linux.alibaba.com>
Date:   Mon, 21 Aug 2023 11:22:31 +0800
From:   Hao Xiang <hao.xiang@...ux.alibaba.com>
To:     kvm@...r.kernel.org
Cc:     shannon.zhao@...ux.alibaba.com, pbonzini@...hat.com,
        seanjc@...gle.com, linux-kernel@...r.kernel.org,
        Hao Xiang <hao.xiang@...ux.alibaba.com>
Subject: [PATCH] kvm: x86: emulate MSR_PLATFORM_INFO msr bits

For intel platform, The BzyMhz field of Turbostat shows zero
due to the missing of part msr bits of MSR_PLATFORM_INFO.

Acquire necessary msr bits, and expose following msr info to guest,
to make sure guest can get correct turbo frequency info.

MSR_PLATFORM_INFO bits
bit 15:8, Maximum Non-Turbo Ratio (MAX_NON_TURBO_LIM_RATIO)
bit 47:40, Maximum Efficiency Ratio (MAX_EFFICIENCY_RATIO)

Signed-off-by: Hao Xiang <hao.xiang@...ux.alibaba.com>
---
 arch/x86/include/asm/msr-index.h |  4 ++++
 arch/x86/kvm/x86.c               | 25 ++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 1d11135..1c8a276 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -68,6 +68,10 @@
 #define MSR_PLATFORM_INFO		0x000000ce
 #define MSR_PLATFORM_INFO_CPUID_FAULT_BIT	31
 #define MSR_PLATFORM_INFO_CPUID_FAULT		BIT_ULL(MSR_PLATFORM_INFO_CPUID_FAULT_BIT)
+/* MSR_PLATFORM_INFO bit 15:8, Maximum Non-Turbo Ratio (MAX_NON_TURBO_LIM_RATIO) */
+#define MSR_PLATFORM_INFO_MAX_NON_TURBO_LIM_RATIO	0x00000000ff00
+/* MSR_PLATFORM_INFO bit 47:40, Maximum Efficiency Ratio (MAX_EFFICIENCY_RATIO) */
+#define MSR_PLATFORM_INFO_MAX_EFFICIENCY_RATIO		0xff0000000000
 
 #define MSR_IA32_UMWAIT_CONTROL			0xe1
 #define MSR_IA32_UMWAIT_CONTROL_C02_DISABLE	BIT(0)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c381770..621c3e1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1679,6 +1679,29 @@ static u64 kvm_get_arch_capabilities(void)
 	return data;
 }
 
+
+static u64 kvm_get_msr_platform_info(void)
+{
+	u64 msr_platform_info = 0;
+
+	rdmsrl_safe(MSR_PLATFORM_INFO, &msr_platform_info);
+	/*
+	 * MSR_PLATFORM_INFO bits:
+	 * bit 15:8, Maximum Non-Turbo Ratio (MAX_NON_TURBO_LIM_RATIO)
+	 * bit 31, CPUID Faulting Enabled (CPUID_FAULTING_EN)
+	 * bit 47:40, Maximum Efficiency Ratio (MAX_EFFICIENCY_RATIO)
+	 *
+	 * Emulate part msr bits, expose above msr info to guest,
+	 * to make sure guest can get correct turbo frequency info.
+	 */
+
+	msr_platform_info &= (MSR_PLATFORM_INFO_MAX_NON_TURBO_RATIO |
+			MSR_PLATFORM_INFO_MAX_EFFICIENCY_RATIO);
+	msr_platform_info |= MSR_PLATFORM_INFO_CPUID_FAULT;
+
+	return msr_platform_info;
+}
+
 static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
 {
 	switch (msr->index) {
@@ -11919,7 +11942,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 		goto free_guest_fpu;
 
 	vcpu->arch.arch_capabilities = kvm_get_arch_capabilities();
-	vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;
+	vcpu->arch.msr_platform_info = kvm_get_msr_platform_info();
 	kvm_xen_init_vcpu(vcpu);
 	kvm_vcpu_mtrr_init(vcpu);
 	vcpu_load(vcpu);
-- 
1.8.3.1