linux-kernel - Re: [PATCH 2/5] perf, x86: AMD implementation for hardware breakpoint address mask

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Message-ID: <20130421171921.GA6645@redhat.com>
Date:	Sun, 21 Apr 2013 19:19:21 +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 2/5] perf, x86: AMD implementation for hardware
	breakpoint address mask

Not a comment, but the question...

On 04/09, Jacob Shin wrote:
>
> --- a/arch/x86/include/asm/hw_breakpoint.h
> +++ b/arch/x86/include/asm/hw_breakpoint.h
> @@ -14,6 +14,7 @@ struct arch_hw_breakpoint {
>  	unsigned long	address;
>  	u8		len;
>  	u8		type;
> +	u32		mask;
>  };
...
> @@ -254,6 +258,7 @@ static int arch_build_bp_info(struct perf_event *bp)
>  	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
>
>  	info->address = bp->attr.bp_addr;
> +	info->mask = bp->attr.bp_addr_mask;

OK, this matches the usage of info->address so I think this change
is right.

But otoh, why do we need info->address (or mask added by this patch)?
we could use bp->attr.bp_addr instead. arch_hw_breakpoint could have
a single filed = "type | len" for encode_dr7().

Yes, off-topic, sorry for noise.

Oleg.

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