On Tue, Aug 07, 2012 at 01:47:52PM -0700, Suresh Siddha wrote: > 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) { > ... No, there's one IOMMU and one IOAPIC, so this check doesn't catch it. The problem is that the ids in the ACPI tables for the devices don't match. > > > 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. I already sent the patch, but where I added it is in intel_enable_irq_remapping(), just after the call to parse_ioapics_under_ir(). But it would be no problem to move it if that makes more sense. Seth -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html