From: "H. Peter Anvin" <hpa@zytor.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>, 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>
Subject: Re: [PATCH] x86: make DR*_RESERVED unsigned long
Date: Wed, 24 Apr 2013 18:20:33 -0700 [thread overview]
Message-ID: <517884E1.5060404@zytor.com> (raw)
In-Reply-To: <CAFTL4hyCQ1DGg5JOmWgvZoC9kcrV6TmodCw=TCFcr+QXMwv9yQ@mail.gmail.com>
On 04/24/2013 04:31 PM, Frederic Weisbecker wrote:
>>
>> Now, DR6 is a bit special in that a bunch of the reserved bits are
>> hardwired to 1, not 0; I don't know offhand if that is true for bits
>> [63:32].
>
> Hmm, good point, could it be a problem given that we clear the
> reserved dr6 bits on do_trap() and write that 'cleaned up" value back
> to "tsk->thread.debugreg6"? Probably not if those hardwired reserved
> bits are set to "1" on dr6 physical write whether those bits are
> cleared or not in their storage in thread struct before resuming the
> task?
>
OK, the SDM states that DR6[63:32] are reserved and must be written as
zero (not one).
So the quiescent 64-bit value of DR6 is 0x0000_0000_FFFF_0FF0.
-hpa
next prev parent reply other threads:[~2013-04-25 1:21 UTC|newest]
Thread overview: 41+ 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
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 [this message]
2013-04-26 14:20 ` [tip:perf/core] perf/x86/intel/P4: Robistify P4 PMU types tip-bot for Ingo Molnar
2013-04-26 16:13 ` Borislav Petkov
2013-04-26 16:24 ` Cyrill Gorcunov
2013-04-26 16:39 ` Borislav Petkov
2013-04-26 16:46 ` Cyrill Gorcunov
2013-04-27 16:14 ` Borislav Petkov
2013-04-27 16:33 ` Cyrill Gorcunov
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