linux-kernel - [PATCH v2 1/7] hyperv: Detect Nested virtualization support for SVM

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Date:   Thu, 15 Apr 2021 13:43:36 +0000
From:   Vineeth Pillai <viremana@...ux.microsoft.com>
To:     Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Wei Liu <wei.liu@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     Vineeth Pillai <viremana@...ux.microsoft.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "K. Y. Srinivasan" <kys@...rosoft.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org
Subject: [PATCH v2 1/7] hyperv: Detect Nested virtualization support for SVM

Detect nested features exposed by Hyper-V if SVM is enabled.

Signed-off-by: Vineeth Pillai <viremana@...ux.microsoft.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 3546d3e21787..c6f812851e37 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -252,6 +252,7 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
 
 static void __init ms_hyperv_init_platform(void)
 {
+	int hv_max_functions_eax;
 	int hv_host_info_eax;
 	int hv_host_info_ebx;
 	int hv_host_info_ecx;
@@ -269,6 +270,8 @@ static void __init ms_hyperv_init_platform(void)
 	ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
 	ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
 
+	hv_max_functions_eax = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
+
 	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
 		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
 		ms_hyperv.misc_features);
@@ -298,8 +301,7 @@ static void __init ms_hyperv_init_platform(void)
 	/*
 	 * Extract host information.
 	 */
-	if (cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS) >=
-	    HYPERV_CPUID_VERSION) {
+	if (hv_max_functions_eax >= HYPERV_CPUID_VERSION) {
 		hv_host_info_eax = cpuid_eax(HYPERV_CPUID_VERSION);
 		hv_host_info_ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
 		hv_host_info_ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
@@ -325,9 +327,11 @@ static void __init ms_hyperv_init_platform(void)
 			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
 	}
 
-	if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
+	if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
 		ms_hyperv.nested_features =
 			cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
+		pr_info("Hyper-V: Nested features: 0x%x\n",
+			ms_hyperv.nested_features);
 	}
 
 	/*
-- 
2.25.1