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Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks

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On Sat, Dec 26, 2015 at 6:15 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Sat, Dec 26, 2015 at 6:08 PM, Tony Luck <tony.luck@gmail.com> wrote:
>> On Sat, Dec 26, 2015 at 6:54 AM, Andy Lutomirski <luto@amacapital.net> wrote:
>>> On Dec 26, 2015 6:33 PM, "Borislav Petkov" <bp@alien8.de> wrote:
>>>> Andy, why is that? It makes the exception handling much simpler this way...
>>>>
>>>
>>> I like the idea of moving more logic into C, but I don't like
>>> splitting the logic across files and adding nasty special cases like
>>> this.
>>>
>>> But what if we generalized it?  An extable entry gives a fault IP and
>>> a landing pad IP.  Surely we can squeeze a flag bit in there.
>>
>> The clever squeezers have already been here. Instead of a pair
>> of 64-bit values for fault_ip and fixup_ip they managed with a pair
>> of 32-bit values that are each the relative offset of the desired address
>> from the table location itself.
>>
>> We could make one of them 31-bits (since even an "allyesconfig" kernel
>> is still much smaller than a gigabyte) to free a bit for a flag. But there
>> are those external tools to pre-sort exception tables that would all
>> need to be fixed too.

Wait, why?  The external tools sort by source address, and we'd
squeeze the flag into the target address, no?

--Andy
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[PATCHV4 0/3] Machine check recovery when kernel accesses poison Tony Luck <tony.luck@intel.com> - 2015-12-24 22:10 +0100
  [PATCHV4 2/3] x86, ras: Extend machine check recovery code to annotated  ring0 areas Tony Luck <tony.luck@intel.com> - 2015-12-24 22:20 +0100
  [PATCHV4 1/3] x86, ras: Add new infrastructure for machine check fixup  tables Tony Luck <tony.luck@intel.com> - 2015-12-24 22:20 +0100
  [PATCHV4 3/3] x86, ras: Add __mcsafe_copy() function to recover from  machine checks Tony Luck <tony.luck@intel.com> - 2015-12-24 22:20 +0100
    Re: [PATCHV4 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-24 22:50 +0100
      [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from  machine checks Tony Luck <tony.luck@intel.com> - 2015-12-25 01:20 +0100
        Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-25 13:00 +0100
          Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks "Luck, Tony" <tony.luck@intel.com> - 2015-12-25 21:10 +0100
            Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-26 11:40 +0100
              Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-26 16:00 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Tony Luck <tony.luck@gmail.com> - 2015-12-27 03:10 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 03:20 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 03:20 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Tony Luck <tony.luck@gmail.com> - 2015-12-27 08:00 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-27 11:20 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 13:30 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks Boris Petkov <bp@alien8.de> - 2015-12-27 14:30 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 14:30 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-27 14:40 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 14:50 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Dan Williams <dan.j.williams@intel.com> - 2015-12-28 03:50 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-27 13:20 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Tony Luck <tony.luck@gmail.com> - 2015-12-31 00:40 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Tony Luck <tony.luck@gmail.com> - 2015-12-31 21:40 +0100
                Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover  from machine checks Andy Lutomirski <luto@amacapital.net> - 2015-12-31 22:30 +0100

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