linux-kernel - [PATCH v2 05/16] KVM: VMX: Drop initialization of IA32_FEATURE

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Message-Id: <20191022000820.1854-1-sean.j.christopherson@intel.com>
Date:   Mon, 21 Oct 2019 17:08:20 -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
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v2 05/16] KVM: VMX: Drop initialization of IA32_FEATURE_CONTROL MSR

Remove the code to initialize IA32_FEATURE_CONTROL MSR when KVM is
loaded now that the MSR is initialized during boot on all CPUs that
support VMX, i.e. can possibly load kvm_intel.

Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 48 +++++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d4575ffb3cec..23c9e4b91b31 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2192,24 +2192,26 @@ static __init int vmx_disabled_by_bios(void)
 	u64 msr;
 
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, msr);
-	if (msr & FEATURE_CONTROL_LOCKED) {
-		/* 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()) {
-			printk(KERN_WARNING "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;
+
+	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;
 }
@@ -2226,7 +2228,6 @@ static int hardware_enable(void)
 {
 	int cpu = raw_smp_processor_id();
 	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
-	u64 old, test_bits;
 
 	if (cr4_read_shadow() & X86_CR4_VMXE)
 		return -EBUSY;
@@ -2254,17 +2255,6 @@ static int hardware_enable(void)
 	 */
 	crash_enable_local_vmclear(cpu);
 
-	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
-
-	test_bits = FEATURE_CONTROL_LOCKED;
-	test_bits |= FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
-	if (tboot_enabled())
-		test_bits |= FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX;
-
-	if ((old & test_bits) != test_bits) {
-		/* enable and lock */
-		wrmsrl(MSR_IA32_FEATURE_CONTROL, old | test_bits);
-	}
 	kvm_cpu_vmxon(phys_addr);
 	if (enable_ept)
 		ept_sync_global();
-- 
2.22.0