linux-kernel - [PATCH RESEND] KVM: nVMX: mask unrestricted

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Date:	Tue, 17 Mar 2015 14:02:32 +0100
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Kashyap Chamarthy <kchamart@...hat.com>, stable@...r.kernel.org
Subject: [PATCH RESEND] KVM: nVMX: mask unrestricted_guest if disabled on L0

If EPT was enabled, unrestricted_guest was allowed in L1 regardless of
L0.  L1 triple faulted when running L2 guest that required emulation.

Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)'
in L0's dmesg:
  WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x96e/0xb00 [kvm_intel] ()

Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when
the host doesn't have it enabled.

Fixes: 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=0")
Cc: stable@...r.kernel.org
Tested-By: Kashyap Chamarthy <kchamart@...hat.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 The resend Cc'd stable, as recommended by Bandan, and added Tested-by.

 arch/x86/kvm/vmx.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 10a481b7674d..ae4f6d35d19c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2479,8 +2479,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	if (enable_ept) {
 		/* nested EPT: emulate EPT also to L1 */
 		vmx->nested.nested_vmx_secondary_ctls_high |=
-			SECONDARY_EXEC_ENABLE_EPT |
-			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+			SECONDARY_EXEC_ENABLE_EPT;
 		vmx->nested.nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT |
 			 VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT |
 			 VMX_EPT_INVEPT_BIT;
@@ -2494,6 +2493,10 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	} else
 		vmx->nested.nested_vmx_ept_caps = 0;
 
+	if (enable_unrestricted_guest)
+		vmx->nested.nested_vmx_secondary_ctls_high |=
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+
 	/* miscellaneous data */
 	rdmsr(MSR_IA32_VMX_MISC,
 		vmx->nested.nested_vmx_misc_low,
-- 
2.3.2

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