Re: [PATCH] enable K7 nmi watchdog

[Mikael Pettersson <mikpe@csd.uu.se>]

On Mon, 15 Jan 2001 04:00:29 +0100, Petr Vandrovec wrote:

>(1) You missed some zeros in MSR_K7_ definitions

Oops :-(

>(2) AMD's MSR are real 64bit (well, 47bit) values, so high
>    MSR dword must be set to -1, not to 0

Correct. That was a copy-paste error from the P6 code.
When writing to a perfctr MSR, Intel P6 sign-extends bit 31.
P5 and Pentium 4 [*], and AMD K7 don't sign-extend, so there one
has to pass -1 in the high word.

[*] P4? PIV? P15? NB? Oh why oh why couldn't they just have named
the core P7 ...

>(3) on my CPU performance register 0x76 counts who knows what...
>    This causes that when machine is idle, there is exactly one
>    NMI per second. When machine is loaded, NMI count/sec climbs
>    up to 100 NMIs per sec. I have no idea whether someone slows
>    clock down to 10MHz on hlt, or what happens. Maybe that they
>    removed this from documentation due to this. This also means
>    that on bootup check for NMI stuck probably passed only
>    due to pure luck - because of mdelay()/udelay() is implemented
>    as tight loop.

The varying speed of this counter is unfortunate, but at least
it doesn't stop completely. The NMI oopser should still trigger,
although perhaps after a much longer delay.

>Otherwise it works

Great. Thanks.

/Mikael
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/