Messages in this thread | | | Date | Mon, 6 Oct 2008 17:00:56 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86 ACPI: Blacklist two HP machines with buggy BIOSes (Re: 2.6.27-rc8+ - first impressions) |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Mon, 6 Oct 2008, Rafael J. Wysocki wrote: > > > > Unfortunately some of the recent IO-APIC changes made the bug show > > up. To prevent this from happening, blacklist machines that are > > known to be affected (nx6115 and 6715b in this particular case). > > Can you point to exactly _which_ recent change made it show up? I'd > really like to know. _What_ was it that made us suddenly need this > quirk when it wasn't necessary before? I'd like to understand the root > cause here. > > And how did you even start looking at that strange ACPI override?
i think it was caused by this stream of IO-APIC changes:
49a66a0: x86: I/O APIC: Always report how the timer has been set up 17c4469: x86: I/O APIC: Include <asm/i8259.h> required by some code 593f4a7: x86: APIC: remove apic_write_around(); use alternatives ce8b06b: x86: I/O APIC: remove an IRQ2-mask hack af17478: x86: I/O APIC: Never configure IRQ2 c88ac1d: x86: L-APIC: Always fully configure IRQ0 1baea6e: x86: L-APIC: Set IRQ0 as edge-triggered
Rafael/Maciej, which of these is causing it? ce8b06b ("x86: I/O APIC: remove an IRQ2-mask hack")?
Current theory is that this specific flavor of BIOS on HP / AMD / Turion laptops (no other type is known to be affected at the moment) somehow detects the IO-APIC masking patterns and uses an SMI quirk to change the ACPI thermal trip point to very low settings, and thus confusing cpufreq to (correctly) go into a very slow frequency.
Activating the quirk works this around. Should we perhaps default to this 'quirk' enabled by default?
Ingo
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