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RE: [Xen-ia64-devel] consoles, iosapics, and device interrupts

To: "Alex Williamson" <alex.williamson@xxxxxx>, <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-ia64-devel] consoles, iosapics, and device interrupts
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Mon, 14 Nov 2005 12:46:53 +0800
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Thread-topic: [Xen-ia64-devel] consoles, iosapics, and device interrupts
>From: Alex Williamson
>Sent: 2005年11月12日 0:27
>   Here's the problem (or at least the start of it); we don't seem to be
>getting any input into the ns16550 driver in the xen hypervisor.  Since
>I'm on an HP box that does not use legacy interrupts for serial lines,
>the interrupt comes in through an IOSAPIC.  We currently don't seem to
>have any support for external interrupts through IOSAPICs.  I thought
>about simply adding polling support to ns16550, but w/o any timer
>support in the hypervisor, that looks non-trivial.  So, I was thinking
>about pulling the IOSAPIC code over.  This means we'll have to iterate
>all the IOSAPICs in the MADT to discover where the GSIs are mapped just
>so we can poke the right one for the serial port.  We can't hide this
>one IOSAPIC RTE from the domains, but unless I missed something, we
>already have IOSAPIC sharing issues if we ever have multiple privileged
>domains with I/O anyway.  

Hi, Alex,
        I second your concern and actually that's the major reason for 
necessity to move IOAPIC ownership into Xen hypervisor and present a virtual 
interrupt controller model to domain. Tristan already made some experiment to 
get serial input/output in Xen, and similar discussion went on following links 
that you may like to look:

>I'm leery to even get into all the issues
>surrounding setting up interrupt polarity and trigger based on the PCDP
>   Does this sound like the right way to go?  I feel like I'm opening a
>can of worms by adding a dependency to an IOSAPIC RTE that we're
>eventually going to hand over to a domain that may clear the interrupt
>vector we want to enable.  Thoughts?  Thanks,
>       Alex
>Alex Williamson                             HP Linux & Open Source Lab
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