Re: [rfc] MSR and System regs for RedBoot target

[Andrew Cagney <ac131313@ges.redhat.com>]

> Andrew Cagney <ac131313@ges.redhat.com> writes:
> 
> 
>> Hello,
>> 
>> The attached (a patch against my sysregs branch) based mostly by code 
>> previously written by Fernando Nasser, adds MSR and system register 
>> support for an i386 RedBoot target.  They each get their own group. 
>> That way:
>> 	info registers msr
>> and 
>> info registers system
>> works (but MSR and SYSTEM registers are not displayed by ``info 
>> registers''.).
> 
> 
> Those system registers seem like a good idea to me.  I'm not so sure
> about those MSRs.

I don't know either here.  I'm going through old lost changes.

>> The patch (apart from demonstrating that reggroups really do work :-) 
>> identifies a number of issues:
>> 
>> - The patch makes RedBoot the default i386 abi -- if nothing else hits, 
>> this gets to be it.  Its done by brute force.  This goes back to the 
>> default discussed earlier for the ``set osabi'' command.  Better re-read 
>> the thread ...
> 
> 
> Does the OS/ABI have to be named "RedBoot"?  I think most of this
> stuff could just as well be added to the generic i386 target.

It depends.

The MSR registers are implemented in a RedBoot specific way - it uses 
target_query() and a qMSR packet.  The qMSR packet came about because 
there are potentially ~4gb of MSR registers and the remote protocol 
doesn't support sparse register numbers.

There are several possible paths here:
- leave qMSR as something RedBoot specific
- formalize it and make it part of the protocol
- provide a mechanism for handling sparse remote protocol register 
numbers so that [Pp] packets can be used.

>> I'll park this in my sysregs branch.  RedBoot is available at 
>> http://sources.redhat.com/redboot/
>> 
>> comments?
> 
> 
> Is there consensus yet on how we should create the types for those
> flag bits?  If we choose Michael Ludvigs approach, this code should be
> converted before we check it in.

Yes, this stuff will need to be updated.
(I need to make those registers lowercase as well).

Andrew