Re: [Xen-devel] Interrupt for HVM guests

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 08/06/2009 20:24, "Emre Can Sezer" <ecsezer@xxxxxxxx> wrote:

> Thanks Keir.  I do have another question though.  I am trying to find
> out whether a page fault occurred during an interrupt handling.  I
> implemented two page tables for HVM guests that help me track execution
> within the guest kernel.  So there is a very good chance that an
> interrupt might also result in a page fault as soon as it is injected.
> I tried counting these events by checking the IF flags in regs->rflags
> and also looking at VIF and VIP flags without success.  Is this a viable
> method for determining whether a page fault was caused during interrupt
> handling?  If not, is there any VM state I can check?

You can easily determine if the page fault happens during interrupt
injection, but once the guest OS starts handling the interrupt it will be
hard to track. The OS is likely to ACK the interrupt quite early and re-set
EFLAGS.IF to 1 before it actually executes the device driver ISR.

 -- Keir



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