Commit 21bd3467 authored by Sean Christopherson's avatar Sean Christopherson Committed by Borislav Petkov
Browse files

KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR 



Remove KVM's code to initialize IA32_FEAT_CTL MSR when KVM is loaded now
that the MSR is initialized during boot on all CPUs that support VMX,
i.e. on all CPUs that can possibly load kvm_intel.

Note, don't WARN if IA32_FEAT_CTL is unlocked, even though the MSR is
unconditionally locked by init_ia32_feat_ctl().  KVM isn't tied directly
to a CPU vendor detection, whereas init_ia32_feat_ctl() is invoked if
and only if the CPU vendor is recognized and known to support VMX.  As a
result, vmx_disabled_by_bios() may be reached without going through
init_ia32_feat_ctl() and thus without locking IA32_FEAT_CTL.  This quirk
will be eliminated in a future patch.

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Link: https://lkml.kernel.org/r/20191221044513.21680-15-sean.j.christopherson@intel.com
parent 85c17291

arch/x86/kvm/vmx/vmx.c

+19 −29
Original line number Diff line number Diff line
@@ -2207,24 +2207,26 @@ static __init int vmx_disabled_by_bios(void) 
	u64 msr;



	rdmsrl(MSR_IA32_FEAT_CTL, msr);

	if (msr & FEAT_CTL_LOCKED) {



	if (unlikely(!(msr & FEAT_CTL_LOCKED)))

		return 1;



	/* launched w/ TXT and VMX disabled */

		if (!(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)

			&& tboot_enabled())

	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()) {

			printk(KERN_WARNING "kvm: disable TXT in the BIOS or "

	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())

	if (!(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX) &&

	    !tboot_enabled())

		return 1;

	}



	return 0;

}
@@ -2241,7 +2243,6 @@ 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;
@@ -2269,17 +2270,6 @@ static int hardware_enable(void) 
	 */

	crash_enable_local_vmclear(cpu);



	rdmsrl(MSR_IA32_FEAT_CTL, old);



	test_bits = FEAT_CTL_LOCKED;

	test_bits |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;

	if (tboot_enabled())

		test_bits |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;



	if ((old & test_bits) != test_bits) {

		/* enable and lock */

		wrmsrl(MSR_IA32_FEAT_CTL, old | test_bits);

	}

	kvm_cpu_vmxon(phys_addr);

	if (enable_ept)

		ept_sync_global();

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