linux-kernel - Re: [PATCH -rt] CONFIG_PARAVIRT and CONFIG

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Message-ID: <20070622152915.GQ3723@sequoia.sous-sol.org>
Date:	Fri, 22 Jun 2007 08:29:15 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH -rt] CONFIG_PARAVIRT and CONFIG_MCOUNT don't play well
	together

* Ingo Molnar (mingo@...e.hu) wrote:
> * Chris Wright <chrisw@...s-sol.org> wrote:
> > Current -rt is broken when compiling with CONFIG_PARAVIRT and 
> > CONFIG_MCOUNT both enabled.  Because CONFIG_MCOUNT disables 
> > CONFIG_REGPARM, the calling convention must once again be explicit 
> > with fastcall.  However, this was only half-way addressed in the -rt 
> > patch (adding fastcall back to paravirt_ops function ptr declaration 
> > but not the actual function definitions) so the compiled kernel has 
> > caller putting stuff in registers and callee pulling things from the 
> > stack. Impressive how far into boot it can get despite that ;-) Thanks 
> > to Steven Rostedt for prodding me and starting the initial debugging.
> 
> thanks! I ran into this before and asked for the fastcalls to not be 
> removed from upstream paravirt.c but to no avail it seems. It does no 
> harm to anyone to keep the 'fastcall' declarations and definitions for 
> places where _actual assembly code_ depends on the calling convention. 
> Could someone please send this upstream-wards too?

Yes, I agree, it's actually documenting the subtlety of the calling
convention, not just noise in the source.  The upstream patch is
different, I'll sort one out.

thanks,
-chris
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