linux-kernel - [tip:x86/pti] KVM/nVMX: Set the CPU_BASED_USE_MSR_BITMAPS if we have a valid L02 MSR bitmap

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Date:   Tue, 13 Feb 2018 00:59:43 -0800
From:   tip-bot for KarimAllah Ahmed <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, bp@...en8.de,
        dan.j.williams@...el.com, dave.hansen@...ux.intel.com,
        rkrcmar@...hat.com, pbonzini@...hat.com, mingo@...nel.org,
        luto@...nel.org, karahmed@...zon.de, peterz@...radead.org,
        arjan@...ux.intel.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        dwmw2@...radead.org, dwmw@...zon.co.uk, gregkh@...uxfoundation.org,
        tglx@...utronix.de, jpoimboe@...hat.com
Subject: [tip:x86/pti] KVM/nVMX: Set the CPU_BASED_USE_MSR_BITMAPS if we
 have a valid L02 MSR bitmap

Commit-ID:  3712caeb14dcb33fb4d5114f14c0beef10aca101
Gitweb:     https://git.kernel.org/tip/3712caeb14dcb33fb4d5114f14c0beef10aca101
Author:     KarimAllah Ahmed <karahmed@...zon.de>
AuthorDate: Sat, 10 Feb 2018 23:39:26 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 13 Feb 2018 09:00:17 +0100

KVM/nVMX: Set the CPU_BASED_USE_MSR_BITMAPS if we have a valid L02 MSR bitmap

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@...zon.de>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: arjan.van.de.ven@...el.com
Cc: dave.hansen@...el.com
Cc: jmattson@...gle.com
Cc: kvm@...r.kernel.org
Cc: sironi@...zon.de
Link: http://lkml.kernel.org/r/1518305967-31356-6-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 599179b..91e3539 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);