KVM: VMX: remove bogus WARN_ON in handle_ept_misconfig

Remove the WARN_ON in handle_ept_misconfig() as it is unnecessary
and causes false positives.  Return the unmodified result of
kvm_mmu_page_fault() instead of converting a system error code to
KVM_EXIT_UNKNOWN so that userspace sees the error code of the
actual failure, not a generic "we don't know what went wrong".

  * kvm_mmu_page_fault() will WARN if reserved bits are set in the
    SPTEs, i.e. it covers the case where an EPT misconfig occurred
    because of a KVM bug.

  * The WARN_ON will fire on any system error code that is hit while
    handling the fault, e.g. -ENOMEM from mmu_topup_memory_caches()
    while handling a legitmate MMIO EPT misconfig or -EFAULT from
    kvm_handle_bad_page() if the corresponding HVA is invalid.  In
    either case, userspace should receive the original error code
    and firing a warning is incorrect behavior as KVM is operating
    as designed.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b2f8a70..39a83a6 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7078,7 +7078,6 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 
 static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
 {
-       int ret;
        gpa_t gpa;
 
        /*
@@ -7106,17 +7105,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
                                                       NULL, 0) == EMULATE_DONE;
        }
 
-       ret = kvm_mmu_page_fault(vcpu, gpa, PFERR_RSVD_MASK, NULL, 0);
-       if (ret >= 0)
-               return ret;
-
-       /* It is the real ept misconfig */
-       WARN_ON(1);
-
-       vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
-       vcpu->run->hw.hardware_exit_reason = EXIT_REASON_EPT_MISCONFIG;
-
-       return 0;
+       return kvm_mmu_page_fault(vcpu, gpa, PFERR_RSVD_MASK, NULL, 0);
 }
 
 static int handle_nmi_window(struct kvm_vcpu *vcpu)