[PATCH v2 08/11] arm64: debug: split hardware watchpoint exception entry

[Mark Rutland]

On Wed, May 28, 2025 at 02:47:52PM +0100, Ada Couprie Diaz wrote:
> On 20/05/2025 17:59, Will Deacon wrote:
> 
> > On Mon, May 12, 2025 at 06:43:23PM +0100, Ada Couprie Diaz wrote:
> > > [...]
> > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> > > index 8814ad24e707..6e70130d2741 100644
> > > --- a/arch/arm64/kernel/entry-common.c
> > > +++ b/arch/arm64/kernel/entry-common.c
> > > @@ -530,10 +530,20 @@ static void noinstr el1_softstp(struct pt_regs *regs, unsigned long esr)
> > >   	arm64_exit_el1_dbg(regs);
> > >   }
> > > -static void noinstr el1_dbg(struct pt_regs *regs, unsigned long esr)
> > > +static void noinstr el1_watchpt(struct pt_regs *regs, unsigned long esr)
> > >   {
> > > +	/* Only watchpoints write FAR_EL1 */
> > nit: But maybe scope the comment (here and in the el0 handler) for debug
> > exceptions?
> > e.g.
> > 
> > 	/* Watchpoints are the only debug exception to write FAR_EL1 */
> > 
> > ?
> > 
> > Will
> 
> Good point. The comment felt somewhat off to me and that's exactly why.
> 
> Updated the wording for v3, thanks.

More of a question for Will, but could we drop the comment entirely?

Historically the same comment in the common el0_dbg() function was a
useful warning because we were forced to read FAR even for
non-watchpoints, but as of this restructuring that awkwardness is gone.

As of this series, for the other debug exceptions, the
el{0,1}_${EXCEPTIONNAME}() handlers don't currently read FAR, and their
callees don't have a 'far' argument.

I'm happy either way, in case you'd prefer that it stays.

Mark.