linux-kernel - [PATCH 5/5] KVM: SVM: Don't allow nested guest to VMMCALL into host

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Date:	Wed, 5 May 2010 16:04:45 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>
CC:	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Joerg Roedel <joerg.roedel@....com>
Subject: [PATCH 5/5] KVM: SVM: Don't allow nested guest to VMMCALL into host

This patch disables the possibility for a l2-guest to do a
VMMCALL directly into the host. This would happen if the
l1-hypervisor doesn't intercept VMMCALL and the l2-guest
executes this instruction.

Signed-off-by: Joerg Roedel <joerg.roedel@....com>
---
 arch/x86/kvm/svm.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index bc087c7..2e9b57a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2036,6 +2036,9 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
 		svm->vmcb->control.intercept_cr_write &= ~INTERCEPT_CR8_MASK;
 	}
 
+	/* We don't want to see VMMCALLs from a nested guest */
+	svm->vmcb->control.intercept &= ~(1ULL << INTERCEPT_VMMCALL);
+
 	/*
 	 * We don't want a nested guest to be more powerful than the guest, so
 	 * all intercepts are ORed
-- 
1.7.1


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