Re: [Xen-devel] xc_hvm_inject_trap() races

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> 11/01/16 10:04 AM >>>
>We've stumbled across the following scenario: we're injecting a #PF to
>try to bring a swapped page back, but Xen already have a pending
>interrupt, and the two collide.
>
>I've logged what happens in hvm_do_resume() at the point of injection,
>and stumbled across this:
>
>(XEN) [  252.878389] vector: 14, type: 3, error_code: 0,
>VM_ENTRY_INTR_INFO: 0x00000000800000e1
>
>VM_ENTRY_INTR_INFO does have INTR_INFO_VALID_MASK set here.

So a first question I have is this: What are the criteria that made your
application decide it needs to inject a trap? Obviously there must have
been some kind of event in the guest that triggered this. Hence the
question is whether this same event wouldn't re-trigger at the end of the
hardware interrupt (or could be made re-trigger reasonably easily).
Because in the end what you're trying to do here is something that's
architecturally impossible: There can't be a (non-nested) exception once
an external interrupt has been accepted (i.e. any subsequent exception
can only be related to the delivery of that interrupt vector, not to the code
which was running when the interrupt was signaled).

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel