KVM: Fix mmu_reload() clash with nested vmx event injection
Currently the inject_pending_event() call during guest entry happens after
kvm_mmu_reload(). This is for historical reasons - we used to
inject_pending_event() in atomic context, while kvm_mmu_reload() needs task
context.
A problem is that nested vmx can cause the mmu context to be reset, if event
injection is intercepted and causes a #VMEXIT instead (the #VMEXIT resets
CR0/CR3/CR4). If this happens, we end up with invalid root_hpa, and since
kvm_mmu_reload() has already run, no one will fix it and we end up entering
the guest this way.
Fix by reordering event injection to be before kvm_mmu_reload(). Use
->cancel_injection() to undo if kvm_mmu_reload() fails.
https://bugzilla.kernel.org/show_bug.cgi?id=42980
Reported-by: Luke-Jr <luke-jr+linuxbugs@utopios.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4de705c..b78f89d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5279,10 +5279,6 @@
kvm_deliver_pmi(vcpu);
}
- r = kvm_mmu_reload(vcpu);
- if (unlikely(r))
- goto out;
-
if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
inject_pending_event(vcpu);
@@ -5298,6 +5294,12 @@
}
}
+ r = kvm_mmu_reload(vcpu);
+ if (unlikely(r)) {
+ kvm_x86_ops->cancel_injection(vcpu);
+ goto out;
+ }
+
preempt_disable();
kvm_x86_ops->prepare_guest_switch(vcpu);