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KVM: VMX: remove bogus WARN_ON in handle_ept_misconfig

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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>
This commit is contained in:
Sean Christopherson 2018-03-29 14:48:31 -07:00 committed by Paolo Bonzini
parent 2c151b2544
commit c75d0edc8e
1 changed files with 1 additions and 12 deletions
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13
arch/x86/kvm/vmx.c
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@ -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)