linux-kernel - [PATCH 07/16] KVM: VMX: Use VMX feature flag to query BIOS enabling

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Date:   Fri,  4 Oct 2019 14:56:06 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Tony W Wang-oc <TonyWWang-oc@...oxin.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-edac@...r.kernel.org,
        Borislav Petkov <bp@...e.de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 07/16] KVM: VMX: Use VMX feature flag to query BIOS enabling

Replace KVM's manual checks on IA32_FEATURE_CONTROL with a query on the
boot CPU's VMX feature flag.  The VMX flag is now cleared during boot if
VMX isn't fully enabled via IA32_FEATURE_CONTROL, including the case
where IA32_FEATURE_CONTROL isn't supported.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 26 +-------------------------
 1 file changed, 1 insertion(+), 25 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 23c9e4b91b31..510f8a778fca 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2189,31 +2189,7 @@ static __init int cpu_has_kvm_support(void)
 
 static __init int vmx_disabled_by_bios(void)
 {
-	u64 msr;
-
-	rdmsrl(MSR_IA32_FEATURE_CONTROL, msr);
-
-	if (WARN_ON_ONCE(!(msr & FEATURE_CONTROL_LOCKED)))
-		return 1;
-
-	/* launched w/ TXT and VMX disabled */
-	if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX) &&
-	    tboot_enabled())
-		return 1;
-	/* launched w/o TXT and VMX only enabled w/ TXT */
-	if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX) &&
-	    (msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX) &&
-	    !tboot_enabled()) {
-		pr_warn("kvm: disable TXT in the BIOS or "
-			"activate TXT before enabling KVM\n");
-		return 1;
-	}
-	/* launched w/o TXT and VMX disabled */
-	if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX) &&
-	    !tboot_enabled())
-		return 1;
-
-	return 0;
+	return !boot_cpu_has(X86_FEATURE_VMX);
 }
 
 static void kvm_cpu_vmxon(u64 addr)
-- 
2.22.0