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Re: [Xen-devel] [PATCH][HVM] fix PCI interrupt routing via ACPI

  • To: "Wang, Winston L" <winston.l.wang@xxxxxxxxx>
  • From: "Dave Lively" <dave.lively@xxxxxxxxx>
  • Date: Fri, 13 Oct 2006 12:36:20 -0400
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 13 Oct 2006 09:36:50 -0700
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On 10/13/06, Wang, Winston L <winston.l.wang@xxxxxxxxx> wrote:
Now we cut the apic mode support, always return the pic mode IRQ and
Link, that may be fine, but when we want to expand more apic IRQs, what
are we going to do? Then have to going back if need more IRQs.

If (when?) the device model is changed to have more than 16 IRQ outputs,
I guess there are a couple alternatives to take advantage of it:
  (a) Go back to statically-mapped IRQs into the larger space for APIC mode
      (requires fixing the problem I've avoided here, though that really shouldn't
      be hard ...), OR
  (b) Make the LNKx devices' _PRS methods include IRQs > 16 for APIC
       mode.  This exposes the expanded set of possible IRQs to the
       guest interrupt routing code.  Trivial to implement.

I'm leaning towards (b), of course, since that's a simple extension to what
I've already written here.  Does that seem reasonable?

By the way, does the code working on SMP guest OS (when apic=1)?

I tested it on RHEL4 U2 64 bit SMP guest, which was definitely using the
APIC.  (The original _ADR fix I ran by you last week actually broke APIC
guests since the LNKx _DIS(able) methods started truly disabling emulated
PCI interrupts once they were writing into the proper PCI config space.  This
is what led me down the path to ignoring the PIC/APIC distinction.)  It's
also been (lightly) tested with Win2003 Server with the ACPI HAL (PIC

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