On 02/07/2018 10:16 PM, Paolo Bonzini wrote:
On 07/02/2018 07:25, Wanpeng Li wrote:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 786cd00..445e702 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7458,6 +7458,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, 
struct kvm_run *kvm_run)
                goto out;
+ if (unlikely(vcpu->run->exit_reason == KVM_EXIT_SHUTDOWN)) {
+               r = -EINVAL;
+               goto out;
+       }
        if (vcpu->run->kvm_dirty_regs) {
                r = sync_regs(vcpu);
                if (r != 0)

This most likely breaks triple faults in the usual case where they
should result in resetting the system; the KVM API doesn't say that you
should clear vcpu->run->exit_reason before entering.

What exactly causes the EPT misconfig to reach the WARN?  That is, how
does kvm_mmu_page_fault end up returning a negative errno value?  If I
read the code correctly only tdp_page_fault can do so, so my guess would
be kvm_handle_bad_page:

         if (pfn == KVM_PFN_ERR_RO_FAULT)
                 return RET_PF_EMULATE;

         if (pfn == KVM_PFN_ERR_HWPOISON) {
                 kvm_send_hwpoison_signal(kvm_vcpu_gfn_to_hva(vcpu, gfn),
                 return RET_PF_RETRY;

        /* KVM_PFN_ERR_FAULT */
         return -EFAULT;

Maybe it should return RET_PF_EMULATE, which would cause an emulation
failure and then an exit with KVM_EXIT_INTERNAL_ERROR.

So the root cause is that a running vCPU accessing the memory whose memslot
is being updated (met the condition KVM_MEMSLOT_INVALID is set on the its

The normal #PF handler breaks KVM_RUN and returns -EFAULT to userspace, we'd
better to make ept-misconfig's handler follow this style as well.

Actually, the WARN_ON in ept-misconfig's handler is unnecessary as
kvm_mmu_page_fault() will warn us if it is the real ept misconfig, so we can
simply return kvm_mmu_page_fault().

Reply via email to