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

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Message-Id: <e14dac75ff1088b2c4bea361954b37e414edd03c.1617804573.git.viremana@linux.microsoft.com>
Date:   Wed,  7 Apr 2021 14:41:22 +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 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, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 3546d3e21787..4d364acfe95d 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -325,9 +325,17 @@ 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) {
+	/*
+	 * AMD does not need enlightened VMCS as VMCB is already a
+	 * datastructure in memory. We need to get the nested
+	 * features if SVM is enabled.
+	 */
+	if (boot_cpu_has(X86_FEATURE_SVM) ||
+	    ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
 		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