Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE

From	Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE
Date	2016-11-03 11:30 +0100
Message-ID	<sznrs-2Dk-9@gated-at.bofh.it> (permalink)
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On Thursday 03 November 2016 03:18 PM, Michael Ellerman wrote:
> Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> writes:
>
>> On Thursday 03 November 2016 02:34 AM, Anton Blanchard wrote:
>>> Hi Ravi,
>>>
>>>> emulate_step() uses a number of underlying kernel functions that were
>>>> initially not enabled for LE. This has been rectified since. So, fix
>>>> emulate_step() for LE for the corresponding instructions.
>>> Thanks. Should this be queued up for stable?
>> Thanks Anton. Yes, this should go in stable.
> It's fairly big for stable. Does it fix an actual bug? If so what, and
> how bad is it, what's the user impact.

Hi Michael,

Yes, kernel-space hw-breakpoint feature is broken on LE without this.

Actually, there is no specific commit that introduced this. Back
in 2010, Paul Mackerras has added emulation support for load/store
instructions for BE. hw-breakpoint was also develpoed by K.Prasad
in the same timeframe.

Kernel-space hw-breakpoint emulates causative instruction before
notifying to user. As emulate_step is never enabled for LE, kernel-
space hw-breakpoint is always broken on LE.

-Ravi

> Can you also pinpoint which commit it "fixes"?
>
> cheers
>

Thread

[PATCH 1/3] powerpc: Emulation support for load/store instructions on LE Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-11-02 10:00 +0100
  Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Anton Blanchard <anton@samba.org> - 2016-11-02 22:10 +0100
    Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-11-03 06:50 +0100
      Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE Michael Ellerman <mpe@ellerman.id.au> - 2016-11-03 10:50 +0100
        Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-11-03 11:30 +0100
          Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Andrew Donnellan <andrew.donnellan@au1.ibm.com> - 2016-11-04 03:10 +0100
            Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-11-04 06:40 +0100
              Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Anton Blanchard <anton@samba.org> - 2016-11-05 20:40 +0100
                Re: [PATCH 1/3] powerpc: Emulation support for load/store  instructions on LE Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-11-06 20:10 +0100

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