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Subject[PATCH v4 6/7] x86/hyper-v: detect nested features
Date
TLFS 5.0 says: "Support for an enlightened VMCS interface is reported with
CPUID leaf 0x40000004. If an enlightened VMCS interface is supported,
additional nested enlightenments may be discovered by reading the CPUID
leaf 0x4000000A (see 2.4.11)."

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
arch/x86/include/asm/hyperv-tlfs.h | 4 ++++
arch/x86/include/asm/mshyperv.h | 1 +
arch/x86/kernel/cpu/mshyperv.c | 4 ++++
3 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 07e0547ae8b8..99139c8e952b 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -21,6 +21,7 @@
#define HYPERV_CPUID_FEATURES 0x40000003
#define HYPERV_CPUID_ENLIGHTMENT_INFO 0x40000004
#define HYPERV_CPUID_IMPLEMENT_LIMITS 0x40000005
+#define HYPERV_CPUID_NESTED_FEATURES 0x4000000A

#define HYPERV_HYPERVISOR_PRESENT_BIT 0x80000000
#define HYPERV_CPUID_MIN 0x40000005
@@ -339,6 +340,9 @@ struct hv_tsc_emulation_status {
#define HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_MASK \
(~((1ull << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) - 1))

+/* Hyper-V Enlightened VMCS version mask in nested features CPUID */
+#define HV_X64_ENLIGHTENED_VMCS_VERSION 0xff
+
#define HV_X64_MSR_TSC_REFERENCE_ENABLE 0x00000001
#define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT 12

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 3f162353f180..57c65315b60b 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -13,6 +13,7 @@ struct ms_hyperv_info {
u32 features;
u32 misc_features;
u32 hints;
+ u32 nested_features;
u32 max_vp_index;
u32 max_lp_index;
};
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 0dfc568c110c..8432bf215e30 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -208,6 +208,10 @@ static void __init ms_hyperv_init_platform(void)
x86_platform.calibrate_cpu = hv_get_tsc_khz;
}

+ if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED)
+ ms_hyperv.nested_features =
+ cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
+
#ifdef CONFIG_X86_LOCAL_APIC
if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
--
2.14.3
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