linux-kernel - Re: [PATCH 02/14] arm64: Call ARCH_WORKAROUND

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Message-ID: <20180524105205.rq25srimaceo3ov4@lakrids.cambridge.arm.com>
Date:   Thu, 24 May 2018 11:52:06 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Julien Grall <julien.grall@....com>
Cc:     Marc Zyngier <marc.zyngier@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 02/14] arm64: Call ARCH_WORKAROUND_2 on transitions
 between EL0 and EL1

On Wed, May 23, 2018 at 10:23:20AM +0100, Julien Grall wrote:
> Hi Marc,
> 
> On 05/22/2018 04:06 PM, Marc Zyngier wrote:
> > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> > index ec2ee720e33e..f33e6aed3037 100644
> > --- a/arch/arm64/kernel/entry.S
> > +++ b/arch/arm64/kernel/entry.S
> > @@ -18,6 +18,7 @@
> >    * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> >    */
> > +#include <linux/arm-smccc.h>
> >   #include <linux/init.h>
> >   #include <linux/linkage.h>
> > @@ -137,6 +138,18 @@ alternative_else_nop_endif
> >   	add	\dst, \dst, #(\sym - .entry.tramp.text)
> >   	.endm
> > +	// This macro corrupts x0-x3. It is the caller's duty
> > +	// to save/restore them if required.
> 
> NIT: Shouldn't you use /* ... */ for multi-line comments?

There's no requirement to do so, and IIRC even Torvalds prefers '//'
comments for multi-line things these days.

Mark.