linux-kernel - Re: [PATCH LINUX] xen: event channel arrays are xen_ulong

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Date:	Tue, 19 Feb 2013 17:26:45 +0000
From:	Tim Deegan <tim@....org>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...e.com>,
	"Keir (Xen.org)" <keir@....org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long

At 17:17 +0000 on 19 Feb (1361294248), Ian Campbell wrote:
> On Tue, 2013-02-19 at 17:11 +0000, Stefano Stabellini wrote:
> > On Tue, 19 Feb 2013, Ian Campbell wrote:
> > > +/*
> > > + * We cannot use xchg because it does not support 8-byte
> > > + * values. However it is safe to use {ldr,dtd}exd directly because all
> > > + * platforms which Xen can run on support those instructions.
> > > + */
> > > +static inline xen_ulong_t xchg_xen_ulong(xen_ulong_t *ptr, xen_ulong_t val)
> > > +{
> > > +       xen_ulong_t oldval;
> > > +       unsigned int tmp;
> > > +
> > > +       wmb();
> > > +       asm volatile("@ read_evtchn_pending_sel\n"
> >                            ^ do we need this?
> 
> It means that the .s files (if you create them) and such are a bit more
> readable, it's not that uncommon in the ARM inline assembly.

+1.  s/read_evtchn_pending_sel/xchg_xen_ulong/ though.

Tim.
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