linux-kernel - Re: [PATCH 01/21] NTB: correct missing readq/writeq errors

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Message-ID: <20130121204741.GA10361@kroah.com>
Date:	Mon, 21 Jan 2013 12:47:41 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Jon Mason <jon.mason@...el.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Dave Jiang <dave.jiang@...el.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: Re: [PATCH 01/21] NTB: correct missing readq/writeq errors

On Mon, Jan 21, 2013 at 08:34:53PM +0000, Ben Hutchings wrote:
> On Mon, 2013-01-21 at 10:23 -0800, Greg KH wrote:
> > On Mon, Jan 21, 2013 at 10:38:18AM -0700, Jon Mason wrote:
> > > On Sun, Jan 20, 2013 at 03:40:05PM -0800, Greg KH wrote:
> > > > On Sat, Jan 19, 2013 at 02:02:15AM -0700, Jon Mason wrote:
> > > > > Atomic readq and writeq do not exist by default on some 32bit
> > > > > architectures, thus causing compile errors due to non-existent symbols.
> > > > > In those cases, use the definitions of those symbols from
> > > > > include/asm-generic/io-64-nonatomic-hi-lo.h
> > > > > 
> > > > > Signed-off-by: Jon Mason <jon.mason@...el.com>
> > > > > ---
> > > > >  drivers/ntb/ntb_hw.c |    1 +
> > > > >  1 file changed, 1 insertion(+)
> > > > > 
> > > > > diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
> > > > > index 4c71b17..0b46fef 100644
> > > > > --- a/drivers/ntb/ntb_hw.c
> > > > > +++ b/drivers/ntb/ntb_hw.c
> > > > > @@ -45,6 +45,7 @@
> > > > >   * Contact Information:
> > > > >   * Jon Mason <jon.mason@...el.com>
> > > > >   */
> > > > > +#include <asm-generic/io-64-nonatomic-hi-lo.h>
> > > > 
> > > > Really?  This seems really odd.  Usually we just don't build the code
> > > > for any platform that doesn't have readq/writeq.  Otherwise, shouldn't
> > > > those arches just include this file themselves to keep everything
> > > > working?  Individual drivers shouldn't have to do this.
> > > 
> > > There is no readq/writeq for 32bit x86.  I was using this header file
> > > to get around that.  I freely admit that I have done 0 testing on
> > > 32bit, but it should work.  If you prefer I modify the Kconfig to only
> > > enable this for x86_64 until such time as I test on x86_32, I will
> > > happily submit that patch.
> > 
> > No, other drivers on 32bit x86 also use readq,
> 
> I don't think so, because it's not defined for CONFIG_X86_32.

Ah, you are right, I was confused by drivers/char/hpet.c, which used
readq, but only on 64bit processors.

Jon, as you say you never tested this on 32bit processors, I'd recommend
just making the Kconfig file enforce that and only build on x86-64 for
now.

thanks,

greg k-h
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