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

[Andrew Cagney <ac131313 at ges dot redhat dot 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