kdb: add rdmsr and wrmsr commands for i386

[Keith Owens]

Bernardo Innocenti (on Thu, 17 May 2007 02:36:21 -0400) wrote:
>Keith Owens wrote:
>
>> Before using MSR, you must first check that the cpu supports the
>> instruction, rd/wrmsr cause an oops on 486 or earlier.  Also using an
>> invalid msr number causes an oops, so use rd/wrmsr_safe().
>
>I didn't bother implementing those checks because kdb recovers
>nicely from GPF anyway.

Yes and no.  Yes, kdb will recover from a GPF.  No, because if the
system was already running correctly (i.e. manual entry into kdb), then
taking a GPF and not recovering will flag the rest of the system as
corrupt and can kill a running system.  I try to avoid adding spurious
system corruption.

>It's the valid MSR writes that could
>cause unrecoveable problems! :)

Tell me about it :-(