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Commit c75d0edc authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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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: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2c151b25

arch/x86/kvm/vmx.c

+1 −12
Original line number Diff line number Diff line
@@ -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)