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: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://lkml.kernel.org/r/20191221044513.21680-15-sean.j.christopherson@intel.com

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 91b2517..a026334 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -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) {
-               /* 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()) {
-                       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 & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX)
-                       && !tboot_enabled())
-                       return 1;
+
+       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;
 }
@@ -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();