From: "H. Peter Anvin" <hpa@zytor.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
David Miller <davem@davemloft.net>,
"Theodore Ts'o" <tytso@mit.edu>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Network Development <netdev@vger.kernel.org>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
Fr??d??ric Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH v2] x86: make DR*_RESERVED unsigned long
Date: Fri, 26 Apr 2013 09:44:05 -0700 [thread overview]
Message-ID: <517AAED5.7040400@zytor.com> (raw)
In-Reply-To: <20130426163802.GA30351@redhat.com>
On 04/26/2013 09:38 AM, Oleg Nesterov wrote:
> DR6_RESERVED and DR_CONTROL_RESERVED are used to clear the set
> bits in the "unsigned long" data, make them long to ensure that
> "&~" doesn't clear the upper bits.
>
> This is only cleanup, the usage of ~DR*_RESERVED is safe but
> doesn't look clean and the pattern is error prone.
>
> - do_debug:
>
> dr6 &= ~DR6_RESERVED;
>
> this also wrongly clears 32-63 bits. Fortunately these
> bits are reserved and must be zero.
>
I don't think this is wrongly at all. The whole point is to mask out
the bits that the handler doesn't want to deal with, so masking out the
reserved bits [63:32] seems reasonable to me.
The comment should probably be corrected, though.
-hpa
next prev parent reply other threads:[~2013-04-26 16:44 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CA+55aFwpLu0qNms=hkQr43yqD0K9DgESNm91OEWKT1ZuT8MU6Q@mail.gmail.com>
2013-04-23 0:23 ` Unsigned widening casts of binary "not" operations Linus Torvalds
2013-04-23 8:59 ` David Laight
2013-04-23 14:29 ` Linus Torvalds
2013-04-23 15:24 ` David Laight
2013-04-23 15:42 ` Linus Torvalds
2013-04-23 15:52 ` Theodore Ts'o
2013-04-23 16:05 ` Linus Torvalds
2013-04-23 17:37 ` David Miller
2013-04-23 17:52 ` Linus Torvalds
2013-04-23 17:56 ` David Miller
2013-04-23 18:21 ` Linus Torvalds
2013-04-24 12:36 ` Geert Uytterhoeven
2013-04-23 0:32 ` H. Peter Anvin
2013-04-23 13:00 ` Theodore Ts'o
2013-04-24 7:26 ` Ingo Molnar
2013-04-24 7:47 ` Cyrill Gorcunov
2013-04-25 1:13 ` Lin Ming
2013-04-24 17:07 ` [PATCH] x86: make DR*_RESERVED unsigned long Oleg Nesterov
2013-04-24 18:45 ` H. Peter Anvin
2013-04-25 14:48 ` Oleg Nesterov
2013-04-26 16:38 ` [PATCH v2] " Oleg Nesterov
2013-04-26 16:44 ` H. Peter Anvin [this message]
2013-04-26 17:15 ` Oleg Nesterov
2013-04-27 14:45 ` Oleg Nesterov
2013-04-27 16:20 ` H. Peter Anvin
2013-04-28 0:58 ` Frederic Weisbecker
2013-04-28 17:27 ` Oleg Nesterov
2013-04-28 17:32 ` H. Peter Anvin
2013-04-28 17:39 ` Oleg Nesterov
2013-04-28 17:43 ` H. Peter Anvin
2013-04-24 22:48 ` [PATCH] " Frederic Weisbecker
2013-04-24 23:06 ` H. Peter Anvin
2013-04-24 23:31 ` Frederic Weisbecker
2013-04-25 1:20 ` H. Peter Anvin
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