linux-kernel - Re: [PATCH 7/24] consolidate msr.h

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Message-ID: <Pine.LNX.4.58.0711200108510.4062@gandalf.stny.rr.com>
Date:	Tue, 20 Nov 2007 01:14:11 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Bastian Blank <bastian@...di.eu.org>,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	glommer@...il.com, tglx@...utronix.de, rusty@...tcorp.com.au,
	ak@...e.de, chrisw@...s-sol.org, avi@...ranet.com,
	anthony@...emonkey.ws, virtualization@...ts.linux-foundation.org,
	lguest@...abs.org, kvm-devel@...ts.sourceforge.net,
	zach@...are.com, jun.nakajima@...el.com
Subject: Re: [PATCH 7/24] consolidate msr.h



On Tue, 20 Nov 2007, Ingo Molnar wrote:

> * Steven Rostedt <rostedt@...dmis.org> wrote:
>
> > With PVOPS on it gives compiler warnings without that explict cast.
> > Without looking at the code, IIRC with non-PVOPS it is a macro
> > directly into asm, so it didn't matter what the cast was. But with
> > PVOPS as a function, it gave compiler warnings.
> >
> > Take it out and try compiling it for both i386 and x86_64. One of them
> > gave warnings. But maybe it's not a problem now.
>
> i dont think there's ever any true need (and good cause) to force
> integer type casts like that at the callee site.

I guess the problem is that we converted a macro to a function, where the
macro did no type checking. Now we need to pick between integers and
pointers. Some places uses intergers in wrmsrl and some use pointers. So
changing this to a typechecking protocol is not going to be nice.

Looking at the current code now, we have this:

====
	checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
	checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
	checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);

	wrmsrl(MSR_CSTAR, ia32_cstar_target);
====

A typecast is already used in that same area.

-- Steve


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