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[Xen-devel] Re: [PATCH RFC] x86/acpi: don't ignore I/O APICs just becaus

To: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH RFC] x86/acpi: don't ignore I/O APICs just because there's no local APIC
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Fri, 12 Jun 2009 11:33:49 -0700
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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On 06/12/09 11:28, Alan Cox wrote:
+               if (error == -EINVAL) {
+                       /*
+                        * The ACPI tables themselves were malformed.
+                        * Dell Precision Workstation 410, 610 come here.
+                        */
+                       printk(KERN_ERR PREFIX
+                              "Invalid BIOS MADT, disabling ACPI\n");
+                       disable_acpi();
+               } else {

This seems a very bad model. On todays systems turning off ACPI renders
them basically useless. If the MADT is bogus its far better to pray that
they rest of the ACPI is mostly sound and continue by ignoring the only
dodgy table.

I didn't make any change there; I just preserved the original behaviour of stopping all ACPI parsing when it returned -EINVAL (with a slightly more helpful comment). My change was to make it continue to the I/O APICs if it returned something else (ie, -ENODEV).

    J

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