From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir@xensource.com>
Subject: Re: Question about evtchn_callback reentry
Date: Mon, 18 Dec 2006 09:31:33 +0000
Message-ID: <C1AC1075.5FF3%keir@xensource.com>
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To: "Xu, Anthony" <anthony.xu@intel.com>
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On 18/12/06 5:28 am, "Xu, Anthony" <anthony.xu@intel.com> wrote:

> If there is no special handling, low privileged interrupt may
> "interrupt" high privileged interrupt.

There's no concept of privilege among event channels. Since Xen simply
allocates ExtInts to vectors in a round-robin manner, there is no meaningful
priority comparsion to be made between vectors anyway.

> BTW,
> I do see evtchn_callback reentry happen on IPF dom0, and that incur
> about 5% performance degradation
> with KB on VTI-domain compared to non_reentry.

KB == Keyboard?!

Reentry is allowed -- it shouldn't happen often unless the ISRs are really
long (bad) or we are hammering the interrupt line for some reason (bad).

 -- Keir