From: Fenghua Yu <fenghua.yu@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Ingo Molnar <mingo@redhat.com>, H Peter Anvin <hpa@zytor.com>,
Ashok Raj <ashok.raj@intel.com>, Alan Cox <alan@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Rafael Wysocki <rafael.j.wysocki@intel.com>,
Tony Luck <tony.luck@intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v2 2/4] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access
Date: Fri, 29 Jun 2018 13:38:44 -0700 [thread overview]
Message-ID: <20180629203844.GA68178@romley-ivt3.sc.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1806292148510.1595@nanos.tec.linutronix.de>
On Fri, Jun 29, 2018 at 10:08:59PM +0200, Thomas Gleixner wrote:
> On Fri, 29 Jun 2018, Fenghua Yu wrote:
>
> > On Fri, Jun 29, 2018 at 06:35:39PM +0200, Thomas Gleixner wrote:
> > > On Fri, 29 Jun 2018, Dave Hansen wrote:
> > >
> > > Plus what enforces proper alignment for the other capability related
> > > u32 arrays?
> >
> > Do you want me to enforce unsigned long alignment for all that are used by
> > locked BTS/BTR?
>
> If there are variables which might be unaligned and accessed with locked
> instructions and you have them identified, then why are you asking whether
> they should be fixed?
>
> Ignoring them because they do not trigger #AC right now, is only the
> correct answer if you are a follower of the 'works by chance' cult.
>
> Yeah, I know that most of this industry just works by chance....
>
Ok. I can work on fixing alignment for these instructions in next version.
How to handle data that is used in generic code which can be used on
non-Intel platform? For exmple, if I do this change for struct efi in
include/linux/efi.h because set_bit() sets bits in efi.flags:
- unsigned long flags;
+ unsigned long flags __aligned(unsigned long);
} efi;
People may argue that the alignment unnecessarily increases size of 'efi'
on non-Intel platform which doesn't have split lock issue. Do we care this
argument?
Another question, there will be a bunch of one-line changes for
the alignment (i.e. adding __aligned(unsigned long)) in various files.
Will the changes be put in one big patch or in separate one-liner patches?
Thanks.
-Fenghua
next prev parent reply other threads:[~2018-06-29 20:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-29 14:33 [PATCH v2 0/4] x86/split_lock: Enable #AC exception for split locked accesses Fenghua Yu
2018-06-29 14:33 ` [PATCH v2 1/4] x86/split_lock: Enumerate #AC exception for split locked access feature Fenghua Yu
2018-06-29 14:56 ` Dave Hansen
2018-06-29 16:23 ` Thomas Gleixner
2018-06-29 16:32 ` Dave Hansen
2018-07-04 20:07 ` Eduardo Habkost
2018-07-10 18:45 ` Fenghua Yu
2018-07-10 18:54 ` Dave Hansen
2018-07-10 19:47 ` Thomas Gleixner
2018-07-11 19:59 ` Dave Hansen
2018-07-12 20:00 ` Thomas Gleixner
2018-06-29 14:33 ` [PATCH v2 2/4] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2018-06-29 16:04 ` Dave Hansen
2018-06-29 16:35 ` Thomas Gleixner
2018-06-29 19:03 ` Fenghua Yu
2018-06-29 20:08 ` Thomas Gleixner
2018-06-29 20:38 ` Fenghua Yu [this message]
2018-06-29 20:48 ` Dave Hansen
2018-06-29 21:10 ` Fenghua Yu
2018-06-29 21:44 ` Thomas Gleixner
2018-06-30 0:00 ` Fenghua Yu
2018-06-30 0:14 ` Fenghua Yu
2018-06-30 6:23 ` Thomas Gleixner
2018-07-02 12:18 ` Peter Zijlstra
2018-07-02 14:11 ` Fenghua Yu
2018-06-29 14:33 ` [PATCH v2 3/4] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2018-06-29 16:29 ` Dave Hansen
2018-06-29 16:33 ` Luck, Tony
2018-06-29 17:16 ` Fenghua Yu
2018-06-29 17:29 ` Dave Hansen
2018-06-29 17:39 ` Fenghua Yu
2018-06-29 17:47 ` Dave Hansen
2018-06-29 14:33 ` [PATCH v2 4/4] x86/split_lock: Disable #AC for split locked accesses Fenghua Yu
2018-06-29 16:31 ` Dave Hansen
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