From: KarimAllah Ahmed <karahmed@amazon.de>
Date: Sat, 10 Feb 2018 23:39:26 +0000
Subject: KVM/nVMX: Set the CPU_BASED_USE_MSR_BITMAPS if we have a valid L02
 MSR bitmap
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Git-commit: 3712caeb14dcb33fb4d5114f14c0beef10aca101
Patch-mainline: v4.16-rc2
References: bsc#1068032 CVE-2017-5754

We either clear the CPU_BASED_USE_MSR_BITMAPS and end up intercepting all
MSR accesses or create a valid L02 MSR bitmap and use that. This decision
has to be made every time we evaluate whether we are going to generate the
L02 MSR bitmap.

Before commit:

  d28b387fb74d ("KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL")

... this was probably OK since the decision was always identical.

This is no longer the case now since the MSR bitmap might actually
change once we decide to not intercept SPEC_CTRL and PRED_CMD.

Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arjan.van.de.ven@intel.com
Cc: dave.hansen@intel.com
Cc: jmattson@google.com
Cc: kvm@vger.kernel.org
Cc: sironi@amazon.de
Link: http://lkml.kernel.org/r/1518305967-31356-6-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kvm/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 599179bfb87f..91e3539cba02 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10130,7 +10130,8 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu,
 	if (cpu_has_vmx_msr_bitmap() &&
 	    nested_cpu_has(vmcs12, CPU_BASED_USE_MSR_BITMAPS) &&
 	    nested_vmx_merge_msr_bitmap(vcpu, vmcs12))
-		;
+		vmcs_set_bits(CPU_BASED_VM_EXEC_CONTROL,
+			      CPU_BASED_USE_MSR_BITMAPS);
 	else
 		vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,
 				CPU_BASED_USE_MSR_BITMAPS);