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authorHaozhong Zhang <haozhong.zhang@intel.com>2017-10-10 15:01:22 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2017-10-12 13:54:56 +0200
commit8eb3f87d903168bdbd1222776a6b1e281f50513e (patch)
treeec690565d7bebdb2ef040357769ba2016b22610d
parent829ee279aed43faa5cb1e4d65c0cad52f2426c53 (diff)
KVM: nVMX: fix guest CR4 loading when emulating L2 to L1 exit
When KVM emulates an exit from L2 to L1, it loads L1 CR4 into the guest CR4. Before this CR4 loading, the guest CR4 refers to L2 CR4. Because these two CR4's are in different levels of guest, we should vmx_set_cr4() rather than kvm_set_cr4() here. The latter, which is used to handle guest writes to its CR4, checks the guest change to CR4 and may fail if the change is invalid. The failure may cause trouble. Consider we start a L1 guest with non-zero L1 PCID in use, (i.e. L1 CR4.PCIDE == 1 && L1 CR3.PCID != 0) and a L2 guest with L2 PCID disabled, (i.e. L2 CR4.PCIDE == 0) and following events may happen: 1. If kvm_set_cr4() is used in load_vmcs12_host_state() to load L1 CR4 into guest CR4 (in VMCS01) for L2 to L1 exit, it will fail because of PCID check. As a result, the guest CR4 recorded in L0 KVM (i.e. vcpu->arch.cr4) is left to the value of L2 CR4. 2. Later, if L1 attempts to change its CR4, e.g., clearing VMXE bit, kvm_set_cr4() in L0 KVM will think L1 also wants to enable PCID, because the wrong L2 CR4 is used by L0 KVM as L1 CR4. As L1 CR3.PCID != 0, L0 KVM will inject GP to L1 guest. Fixes: 4704d0befb072 ("KVM: nVMX: Exiting from L2 to L1") Cc: qemu-stable@nongnu.org Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/vmx.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a2b804e10c95..95a01609d7ee 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11297,7 +11297,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
/* Same as above - no reason to call set_cr4_guest_host_mask(). */
vcpu->arch.cr4_guest_owned_bits = ~vmcs_readl(CR4_GUEST_HOST_MASK);
- kvm_set_cr4(vcpu, vmcs12->host_cr4);
+ vmx_set_cr4(vcpu, vmcs12->host_cr4);
nested_ept_uninit_mmu_context(vcpu);