linux-kernel - Re: [PATCH 1/5] perf: Add hardware breakpoint address mask

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Message-ID: <20130421170202.GA5358@redhat.com>
Date:	Sun, 21 Apr 2013 19:02:02 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jacob Shin <jacob.shin@....com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Stephane Eranian <eranian@...gle.com>,
	Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] perf: Add hardware breakpoint address mask

On 04/20, Jacob Shin wrote:
>
> On Sat, Apr 20, 2013 at 06:53:34PM +0200, Oleg Nesterov wrote:
> >
> > And does attr.bp_len "contribute" to the mask?
> >
> > I mean, if bp_len == X86_BREAKPOINT_LEN_8, does this mean that
> > bp_bp_addr_mask and (bp_bp_addr_mask | 7) have the same effect?
>
> Yes it has the same effect.

OK, thanks...

So this is the "natural" extension. Given that currently bp_addr
should be aligned, bp_len could be already bp_mask but I guess it
is too late to change this, so we need another field.

Hmm. Perhaps arch_has_hw_breakpoint_addr_mask(void) should be turned
into arch_validate_hw_breakpoint_addr_mask(bp) which should also
check that (bp_addr & bp_addr_mask) == 0. But I won't insist.

Oleg.

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