[tip: x86/cpu] KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR

tip-bot2 for Sean Christopherson
2020-01-14T10:17:56Z

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

Commit-ID: 21bd3467a58ea51ccc0b1d9bcb86dadf1640a002
Gitweb: https://git.kernel.org/tip/21bd3467a58ea51ccc0b1d9bcb86dadf1640a002
Author: Sean Christopherson <sean.j.christopherson@intel.com>
AuthorDate: Fri, 20 Dec 2019 20:45:08 -08:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 13 Jan 2020 19:04:37 +01:00

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
---
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 91b2517..a026334 100644
--- 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();