kvm: svm: Ensure an IBPB on all affected CPUs when freeing a vmcb

commit fd65d3142f734bc4376053c8d75670041903134d upstream.

Previously, we only called indirect_branch_prediction_barrier on the
logical CPU that freed a vmcb. This function should be called on all
logical CPUs that last loaded the vmcb in question.

Fixes: 15d45071523d ("KVM/x86: Add IBPB support")
Reported-by: Neel Natu <neelnatu@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5f44d63a9d694fec4ba965ec2e06a1050becf623..4bc35ac28d1199e25b9c1b700c0a32c37f59dccc 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1672,21 +1672,31 @@ out:
        return ERR_PTR(err);
 }
 
+static void svm_clear_current_vmcb(struct vmcb *vmcb)
+{
+       int i;
+
+       for_each_online_cpu(i)
+               cmpxchg(&per_cpu(svm_data, i)->current_vmcb, vmcb, NULL);
+}
+
 static void svm_free_vcpu(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
 
+       /*
+        * The vmcb page can be recycled, causing a false negative in
+        * svm_vcpu_load(). So, ensure that no logical CPU has this
+        * vmcb page recorded as its current vmcb.
+        */
+       svm_clear_current_vmcb(svm->vmcb);
+
        __free_page(pfn_to_page(svm->vmcb_pa >> PAGE_SHIFT));
        __free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
        __free_page(virt_to_page(svm->nested.hsave));
        __free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER);
        kvm_vcpu_uninit(vcpu);
        kmem_cache_free(kvm_vcpu_cache, svm);
-       /*
-        * The vmcb page can be recycled, causing a false negative in
-        * svm_vcpu_load(). So do a full IBPB now.
-        */
-       indirect_branch_prediction_barrier();
 }
 
 static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)