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KVM: x86: Fix misleading comments on handling pending exceptions

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The reason that exception.pending should block re-injection of
NMI/interrupt is not described correctly in comment in code.
Instead, it describes why a pending exception should be injected
before a pending NMI/interrupt.

Therefore, move currently present comment to code-block evaluating
a new pending event which explains why exception.pending is evaluated
first.
In addition, create a new comment describing that exception.pending
blocks re-injection of NMI/interrupt because the exception was
queued by handling vmexit which was due to NMI/interrupt delivery.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@orcle.com>
[Used a comment from Sean J <sean.j.christopherson@intel.com>. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Liran Alon 2018-03-23 03:01:32 +03:00 committed by Radim Krčmář
parent 04140b4144
commit a042c26fd8
1 changed files with 12 additions and 2 deletions
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14
arch/x86/kvm/x86.c
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@ -6758,8 +6758,18 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
}
/*
* Exceptions must be injected immediately, or the exception
* frame will have the address of the NMI or interrupt handler.
* Do not inject an NMI or interrupt if there is a pending
* exception. Exceptions and interrupts are recognized at
* instruction boundaries, i.e. the start of an instruction.
* Trap-like exceptions, e.g. #DB, have higher priority than
* NMIs and interrupts, i.e. traps are recognized before an
* NMI/interrupt that's pending on the same instruction.
* Fault-like exceptions, e.g. #GP and #PF, are the lowest
* priority, but are only generated (pended) during instruction
* execution, i.e. a pending fault-like exception means the
* fault occurred on the *previous* instruction and must be
* serviced prior to recognizing any new events in order to
* fully complete the previous instruction.
*/
if (!vcpu->arch.exception.pending) {
if (vcpu->arch.nmi_injected) {