Re: [PATCH] oprofile add Pentium Mobile support

[Mikael Pettersson]

Philippe Elie writes:
 > From: Will Cohen <wcohen@xxxxxxxxxx>
 > 
 > Add oprofile support for Pentium Mobile (P6 core). Pentium Mobile needs
 > to unmask LVPTC vector, since it doesn't hurt other P6 core based cpus
 > we do it unconditionally for all these.

[Patch talking about the Pentium-M.]

I can find no support in Intel's documentation (IA32 Volume 3,
25366813.pdf) that Pentium-M:s need to unmask LVTPC.

How certain are you of this? Is this an undocumented hardware
quirk? If it is documented, please indicate where.

It's my theory that P4 added the auto-masking to help PEBS
buffer overflow situations, but since P-M doesn't have PEBS,
they shouldn't have had to change this on P-M as well.
OTOH, it's certainly possible they changed it by accident.

One way of testing this would be to run a P-M with
nmi_watchdog=2. If the NMI counter keeps ticking, then
LVTPC does not need unmasking.

/Mikael
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