linux-kernel - [tip: x86/cpu] KVM: VMX: Use VMX feature flag to query BIOS enabling

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Date:   Tue, 14 Jan 2020 10:16:51 -0000
From:   "tip-bot2 for Sean Christopherson" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Borislav Petkov <bp@...e.de>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/cpu] KVM: VMX: Use VMX feature flag to query BIOS enabling

The following commit has been merged into the x86/cpu branch of tip:

Commit-ID:     a4d0b2fdbcf75ef6654713c83c316ea3a661ddc3
Gitweb:        https://git.kernel.org/tip/a4d0b2fdbcf75ef6654713c83c316ea3a661ddc3
Author:        Sean Christopherson <sean.j.christopherson@...el.com>
AuthorDate:    Fri, 20 Dec 2019 20:45:09 -08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 13 Jan 2020 19:19:32 +01:00

KVM: VMX: Use VMX feature flag to query BIOS enabling

Replace KVM's manual checks on IA32_FEAT_CTL with a query on the boot
CPU's MSR_IA32_FEAT_CTL and VMX feature flags.  The MSR_IA32_FEAT_CTL
indicates that IA32_FEAT_CTL has been configured and that dependent
features are accurately reflected in cpufeatures, e.g. the VMX flag is
now cleared during boot if VMX isn't fully enabled via IA32_FEAT_CTL,
including the case where the MSR isn't supported.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20191221044513.21680-16-sean.j.christopherson@intel.com
---
 arch/x86/kvm/vmx/vmx.c | 27 ++-------------------------
 1 file changed, 2 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index a026334..06e0e52 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2204,31 +2204,8 @@ static __init int cpu_has_kvm_support(void)
 
 static __init int vmx_disabled_by_bios(void)
 {
-	u64 msr;
-
-	rdmsrl(MSR_IA32_FEAT_CTL, msr);
-
-	if (unlikely(!(msr & FEAT_CTL_LOCKED)))
-		return 1;
-
-	/* launched w/ TXT and VMX disabled */
-	if (!(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX) &&
-	    tboot_enabled())
-		return 1;
-	/* launched w/o TXT and VMX only enabled w/ TXT */
-	if (!(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX) &&
-	    (msr & FEAT_CTL_VMX_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 & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX) &&
-	    !tboot_enabled())
-		return 1;
-
-	return 0;
+	return !boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
+	       !boot_cpu_has(X86_FEATURE_VMX);
 }
 
 static void kvm_cpu_vmxon(u64 addr)