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Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused the exception.

From Anshuman Khandual <khandual@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused the exception.
Date 2017-06-20 08:50 +0200
Message-ID <tUl98-55H-1@gated-at.bofh.it> (permalink)
References <tTd3X-1kp-3@gated-at.bofh.it> <tTd3Y-1kp-17@gated-at.bofh.it> <tU2Jc-1RM-21@gated-at.bofh.it> <tU97Y-5OJ-9@gated-at.bofh.it>
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On 06/19/2017 11:29 PM, Ram Pai wrote:
> On Mon, Jun 19, 2017 at 09:06:13PM +1000, Michael Ellerman wrote:
>> Ram Pai <linuxram@us.ibm.com> writes:
>>
>>> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
>>> ---
>>>  arch/powerpc/kernel/exceptions-64s.S | 16 ++++++++++------
>>>  1 file changed, 10 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
>>> index 8db9ef8..a4de1b4 100644
>>> --- a/arch/powerpc/kernel/exceptions-64s.S
>>> +++ b/arch/powerpc/kernel/exceptions-64s.S
>>> @@ -493,13 +493,15 @@ EXC_COMMON_BEGIN(data_access_common)
>>>  	ld	r12,_MSR(r1)
>>>  	ld	r3,PACA_EXGEN+EX_DAR(r13)
>>>  	lwz	r4,PACA_EXGEN+EX_DSISR(r13)
>>> +	std	r3,_DAR(r1)
>>> +	std	r4,_DSISR(r1)
>>>  #ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
>>> +	andis.  r0,r4,DSISR_KEYFAULT@h /* save AMR only if its a key fault */
>>> +	beq+	1f
>>
>> This seems to be incremental on top of one of your other patches.
>>
>> But I don't see why, can you please just squash this into whatever patch
>> adds this code in the first place.
> 
> It was an optimization added later. But yes it can be squashed into an
> earlier patch.

Could you please explain what is the optimization this achieves ?

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[RFC v2 00/12] powerpc: Memory Protection Keys Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
  [RFC v2 09/12] powerpc: Deliver SEGV signal on pkey violation. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 09/12] powerpc: Deliver SEGV signal on pkey violation. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 09:00 +0200
      Re: [RFC v2 09/12] powerpc: Deliver SEGV signal on pkey violation. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 02:00 +0200
        Re: [RFC v2 09/12] powerpc: Deliver SEGV signal on pkey violation. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-21 05:20 +0200
          Re: [RFC v2 09/12] powerpc: Deliver SEGV signal on pkey violation. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 08:20 +0200
  [RFC v2 07/12] powerpc: Macro the mask used for checking DSI exception Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI  exception Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 10:20 +0200
      Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI  exception Ram Pai <linuxram@us.ibm.com> - 2017-06-21 01:30 +0200
    Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI exception "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2017-06-21 09:30 +0200
      Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI  exception Ram Pai <linuxram@us.ibm.com> - 2017-06-21 11:20 +0200
  [RFC v2 04/12] powerpc: store and restore the pkey state across context switches. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
  [RFC v2 05/12] powerpc: Implementation for sys_mprotect_pkey() system call. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 05/12] powerpc: Implementation for sys_mprotect_pkey() system call. "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2017-06-21 09:20 +0200
  [RFC v2 11/12]Documentation: Documentation updates. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 11/12]Documentation: Documentation updates. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 08:20 +0200
      Re: [RFC v2 11/12]Documentation: Documentation updates. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 02:10 +0200
  [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 12:30 +0200
      Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 01:30 +0200
        Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-21 07:40 +0200
          Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 08:40 +0200
    Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed hpte pages. "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2017-06-21 08:50 +0200
      Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 11:40 +0200
    Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-22 11:10 +0200
      Re: [RFC v2 01/12] powerpc: Free up four 64K PTE bits in 4K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-22 18:30 +0200
  [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused the exception. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused the exception. Michael Ellerman <mpe@ellerman.id.au> - 2017-06-19 13:10 +0200
      Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused  the exception. Ram Pai <linuxram@us.ibm.com> - 2017-06-19 20:00 +0200
        Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused  the exception. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 08:50 +0200
          Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused  the exception. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 02:00 +0200
      Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused  the exception. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 02:00 +0200
  [RFC v2 03/12] powerpc: Implement sys_pkey_alloc and sys_pkey_free system call. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 03/12] powerpc: Implement sys_pkey_alloc and sys_pkey_free system call. Michael Ellerman <mpe@ellerman.id.au> - 2017-06-19 14:20 +0200
      Re: [RFC v2 03/12] powerpc: Implement sys_pkey_alloc and  sys_pkey_free system call. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 00:50 +0200
  [RFC v2 06/12] powerpc: Program HPTE key protection bits. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 06/12] powerpc: Program HPTE key protection bits. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 10:30 +0200
      Re: [RFC v2 06/12] powerpc: Program HPTE key protection bits. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 01:30 +0200
  [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-17 06:00 +0200
    Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed  hpte pages. Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 13:00 +0200
      Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 01:30 +0200
    Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages. "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2017-06-21 09:00 +0200
      Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed  hpte pages. Ram Pai <linuxram@us.ibm.com> - 2017-06-21 22:20 +0200
    Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages. "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2017-06-21 09:00 +0200
  Re: [RFC v2 12/12]selftest: Updated protection key selftest Michael Ellerman <mpe@ellerman.id.au> - 2017-06-19 13:10 +0200
  Re: [RFC v2 00/12] powerpc: Memory Protection Keys Balbir Singh <bsingharora@gmail.com> - 2017-06-20 07:20 +0200
    Re: [RFC v2 00/12] powerpc: Memory Protection Keys Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 08:10 +0200
    Re: [RFC v2 00/12] powerpc: Memory Protection Keys Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-06-20 12:00 +0200
  Re: [RFC v2 12/12]selftest: Updated protection key selftest Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-06-20 08:30 +0200
    Re: [RFC v2 12/12]selftest: Updated protection key selftest Ram Pai <linuxram@us.ibm.com> - 2017-06-21 02:20 +0200

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