[3.13.y-ckt stable] Patch "KVM: nVMX: mask unrestricted_guest if disabled on L0" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    KVM: nVMX: mask unrestricted_guest if disabled on L0

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 63f1e7459040bc24e841ca5c6c6d4b71f6ed0022 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar at redhat.com>
Date: Tue, 17 Mar 2015 14:02:32 +0100
Subject: KVM: nVMX: mask unrestricted_guest if disabled on L0
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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commit 0790ec172de1bd2e23f1dbd4925426b6cc3c1b72 upstream.

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")
Tested-By: Kashyap Chamarthy <kchamart at redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar at redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti at redhat.com>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kvm/vmx.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2ff437d..9c2c662 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2260,8 +2260,8 @@ static __init void nested_vmx_setup_ctls_msrs(void)

 	if (enable_ept) {
 		/* nested EPT: emulate EPT also to L1 */
-		nested_vmx_secondary_ctls_high |= SECONDARY_EXEC_ENABLE_EPT |
-			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+		nested_vmx_secondary_ctls_high |=
+			SECONDARY_EXEC_ENABLE_EPT;
 		nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT |
 			 VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT |
 			 VMX_EPT_INVEPT_BIT;
@@ -2276,6 +2276,10 @@ static __init void nested_vmx_setup_ctls_msrs(void)
 	} else
 		nested_vmx_ept_caps = 0;

+	if (enable_unrestricted_guest)
+		nested_vmx_secondary_ctls_high |=
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+
 	/* miscellaneous data */
 	rdmsr(MSR_IA32_VMX_MISC, nested_vmx_misc_low, nested_vmx_misc_high);
 	nested_vmx_misc_low &= VMX_MISC_PREEMPTION_TIMER_RATE_MASK |
--
1.9.1