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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 29 Aug 2014 17:43:43 +0100
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Subject: Re: [Qemu-devel] [PATCH 05/10] target-arm: Implement setting of
	watchpoints
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To: Richard Henderson <rth@twiddle.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, =?UTF-8?Q?Andreas_F=C3=A4rber?= <afaerber@suse.de>, Patch Tracking <patches@linaro.org>

On 29 August 2014 17:42, Richard Henderson <rth@twiddle.net> wrote:
> On 08/29/2014 04:21 AM, Peter Maydell wrote:
>> +        /* Watchpoint covers an aligned area up to 2GB in size */
>> +        len = 1ULL << mask;
>> +        /* If masked bits in WVR are not zero it's CONSTRAINED UNPREDICTABLE
>> +         * whether the watchpoint fires when the unmasked bits match; we opt
>> +         * to generate the exceptions.
>> +         */
>> +        wvr &= (len - 1);
>
> This looks funny... address being clipped to length?
> Surely it's ~(len - 1)...

Nice catch. Linux doesn't actually use this bit of the watchpoint
functionality, which is why I didn't notice.

-- PMM