Patch "KVM: VMX: fix nested vpid for old KVM guests" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

KVM: VMX: fix nested vpid for old KVM guests

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-vmx-fix-nested-vpid-for-old-kvm-guests.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Paolo Bonzini <[email protected]>
Date: Fri, 18 Mar 2016 16:58:38 +0100
Subject: KVM: VMX: fix nested vpid for old KVM guests

From: Paolo Bonzini <[email protected]>

commit ef697a712a6165aea7779c295604b099e8bfae2e upstream.

Old KVM guests invoke single-context invvpid without actually checking whether it is supported. This was fixed by commit 518c8ae ("KVM: VMX:
Make sure single type invvpid is supported before issuing invvpid instruction", 2010-08-01) and the patch after, but pre-2.6.36 kernels lack it including RHEL 6.

---
 arch/x86/kvm/vmx.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

@@ -2637,8 +2637,15 @@ static void nested_vmx_setup_ctls_msrs(s
 	} else
 		vmx->nested.nested_vmx_ept_caps = 0;
 
+	/*
+	 * Old versions of KVM use the single-context version without
+	 * checking for support, so declare that it is supported even
+	 * though it is treated as global context.  The alternative is
+	 * not failing the single-context invvpid, and it is worse.
+	 */
 	if (enable_vpid)
 		vmx->nested.nested_vmx_vpid_caps = VMX_VPID_INVVPID_BIT |
+				VMX_VPID_EXTENT_SINGLE_CONTEXT_BIT |
 				VMX_VPID_EXTENT_GLOBAL_CONTEXT_BIT;
 	else
 		vmx->nested.nested_vmx_vpid_caps = 0;

@@ -7416,12 +7423,17 @@ static int handle_invvpid(struct kvm_vcp
 	}
 
 	switch (type) {
+	case VMX_VPID_EXTENT_SINGLE_CONTEXT:
+		/*
+		 * Old versions of KVM use the single-context version so we
+		 * have to support it; just treat it the same as all-context.
+		 */
 	case VMX_VPID_EXTENT_ALL_CONTEXT:
 		__vmx_flush_tlb(vcpu, to_vmx(vcpu)->nested.vpid02);
 		nested_vmx_succeed(vcpu);
 		break;
 	default:
-		/* Trap single context invalidation invvpid calls */
+		/* Trap individual address invalidation invvpid calls */
 		BUG_ON(1);
 		break;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/kvm-vmx-fix-nested-vpid-for-old-kvm-guests.patch queue-4.4/kvm-x86-fix-missed-hardware-breakpoints.patch queue-4.4/kvm-vmx-avoid-guest-hang-on-invalid-invvpid-instruction.patch queue-4.4/kvm-i8254-change-pit-discard-tick-policy.patch queue-4.4/kvm-fix-spin_lock_init-order-on-x86.patch queue-4.4/kvm-vmx-avoid-guest-hang-on-invalid-invept-instruction.patch