linux-kernel - [tip: x86/cpu] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

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Message-ID: <157899701402.1022.5566010856636345851.tip-bot2@tip-bot2>
Date:   Tue, 14 Jan 2020 10:16:54 -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] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

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

Commit-ID:     ef4d3bf19855641fc8a1f621eaf06e2a2bb872bb
Gitweb:        https://git.kernel.org/tip/ef4d3bf19855641fc8a1f621eaf06e2a2bb872bb
Author:        Sean Christopherson <sean.j.christopherson@...el.com>
AuthorDate:    Fri, 20 Dec 2019 20:45:02 -08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 13 Jan 2020 17:53:57 +01:00

x86/cpu: Clear VMX feature flag if VMX is not fully enabled

Now that IA32_FEAT_CTL is always configured and locked for CPUs that are
known to support VMX[*], clear the VMX capability flag if the MSR is
unsupported or BIOS disabled VMX, i.e. locked IA32_FEAT_CTL and didn't
set the appropriate VMX enable bit.

[*] Because init_ia32_feat_ctl() is called from vendors ->c_init(), it's
    still possible for IA32_FEAT_CTL to be left unlocked when VMX is
    supported by the CPU.  This is not fatal, and will be addressed in a
    future patch.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20191221044513.21680-9-sean.j.christopherson@intel.com
---
 arch/x86/kernel/cpu/feat_ctl.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
index c4f8f76..a46c9e4 100644
--- a/arch/x86/kernel/cpu/feat_ctl.c
+++ b/arch/x86/kernel/cpu/feat_ctl.c
@@ -5,15 +5,21 @@
 #include <asm/msr-index.h>
 #include <asm/processor.h>
 
+#undef pr_fmt
+#define pr_fmt(fmt)	"x86/cpu: " fmt
+
 void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 {
+	bool tboot = tboot_enabled();
 	u64 msr;
 
-	if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr))
+	if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
+		clear_cpu_cap(c, X86_FEATURE_VMX);
 		return;
+	}
 
 	if (msr & FEAT_CTL_LOCKED)
-		return;
+		goto update_caps;
 
 	/*
 	 * Ignore whatever value BIOS left in the MSR to avoid enabling random
@@ -29,9 +35,20 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM_INTEL)) {
 		msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
 
-		if (tboot_enabled())
+		if (tboot)
 			msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
 	}
 
 	wrmsrl(MSR_IA32_FEAT_CTL, msr);
+
+update_caps:
+	if (!cpu_has(c, X86_FEATURE_VMX))
+		return;
+
+	if ( (tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
+	    (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
+		pr_err_once("VMX (%s TXT) disabled by BIOS\n",
+			    tboot ? "inside" : "outside");
+		clear_cpu_cap(c, X86_FEATURE_VMX);
+	}
 }