Messages in this thread | | | Subject | Re: IRQ remapping problem on Macbook Air 5,1 | From | Suresh Siddha <> | Date | Tue, 07 Aug 2012 13:47:52 -0700 |
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On Tue, 2012-08-07 at 22:10 +0200, Joerg Roedel wrote: > Hi Seth, > > On Tue, Aug 07, 2012 at 02:48:37PM -0500, Seth Forshee wrote: > > This machine has a bug in its ACPI tables that's causing it to fail to > > boot unless intremap=off is passed to the kernel. The MADT defines a > > single IOAPIC with id 2, but the remapping unit defined in DMAR matches > > id 0. Thus interrupt remapping fails, and the kernel panics with the > > message "timer doesn't work through Interrupt-remapped IO-APIC." If I > > force the use of the non-matching ir hardware for the IOAPIC everything > > seems to works fine. dmesg for the working boot is below. > > There are AMD systems with similar problems. For example I had a system > with 2 IO-APICs but only one was described in the IOMMU ACPI table.
This issue should be caught by the current check in parse_ioapics_under_ir()
if (ir_supported && ir_ioapic_num != nr_ioapics) { ...
> > > I'm looking at how to make this machine able to boot by default. OS X > > obviously boots, and Windows presumably boots as well since Apple > > officially supports running Windows on its hardware. > > These operating systems probably don't support interrupt remapping, or > the IOMMU at all.
Some of them use interrupt-remapping only if the bios has pre-enabled x2apic/interrupt-remapping etc. But Linux tries to enable x2apic/interrupt-remapping even if bios doesn't.
> > > I've got a patch to leave IRQ remapping disabled whenever any IOAPIC > > does not have a matching ir hardware unit. This gets it to boot, but I > > thought I'd check and see whether anyone had any better ideas for how to > > fix this. > > This is exactly how I fixed this issue on the AMD side too. Mind to > submit the patch?
yes, we should be able to extend the check in parse_ioapics_under_ir() to check for this condition.
thanks, suresh
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