Re: [PATCH] - x86_64-add-ioapic-nmi-support-fix-3

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John Keller wrote:
[adding Andi Kleen]

John Keller wrote:
Place all the IOACPI NMI support code under CONFIG_ACPI
to clear up build errors with certain configs.

Signed-off-by: John Keller <[email protected]>
---
Is there some architectural reason that IO APIC NMI support should
require ACPI?

OK, I guess standing alone this description was a bit misleading.
The code referred to here is the new code supporting the ACPI NMI SRC
structure that can be specified in the MADT. Without ACPI support this
code is not relevant. All the code touched by this patch was introduced
by eariler versions of this patchset.

This patch makes no changes to the workings of nmi_watchdog.

OK, thanks for the clarification.

John


Is this a new requirement?  It seems like a step backwards to me.


Documentation/nmi_watchdog.txt doesn't say anything about ACPI being
needed.  It does say:

"For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
always enabled with I/O-APIC mode (nmi_watchdog=1). Currently, local APIC
mode (nmi_watchdog=2) does not work on x86-64.

Using local APIC (nmi_watchdog=2) needs the first performance register, so
you can't use it for other purposes (such as high precision performance
profiling.) However, at least oprofile and the perfctr driver disable the
local APIC NMI watchdog automatically."


--
~Randy
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