Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks

From	Borislav Petkov <bp@alien8.de>
Newsgroups	linux.kernel
Subject	Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks
Date	2015-12-15 19:30 +0100
Message-ID	<qG2wi-7PJ-3@gated-at.bofh.it> (permalink)
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On Tue, Dec 15, 2015 at 05:53:31PM +0000, Luck, Tony wrote:
> My current generation cpu has a bit of an issue with recovering from a
> machine check in a "rep mov" ... so I'm working with a version of memcpy
> that unrolls into individual mov instructions for now.

Ah.

> I can drop the "nti" from the destination moves.  Does "nti" work
> on the load from source address side to avoid cache allocation?

I don't think so:

+1:     movq (%rsi),%r8
+2:     movq 1*8(%rsi),%r9
+3:     movq 2*8(%rsi),%r10
+4:     movq 3*8(%rsi),%r11
...

You need to load the data into registers first because MOVNTI needs them
there as it does reg -> mem movement. That first load from memory into
registers with a normal MOV will pull the data into the cache.

Perhaps the first thing to try would be to see what slowdown normal MOVs
bring and if not really noticeable, use those instead.

> On another topic raised by Boris ... is there some CONFIG_PMEM*
> that I should use as a dependency to enable all this?

I found CONFIG_LIBNVDIMM only today:

drivers/nvdimm/Kconfig:1:menuconfig LIBNVDIMM
drivers/nvdimm/Kconfig:2:       tristate "NVDIMM (Non-Volatile Memory Device) Support"

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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Thread

Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-15 14:20 +0100
  Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Dan Williams <dan.j.williams@intel.com> - 2015-12-15 18:50 +0100
    RE: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks "Luck, Tony" <tony.luck@intel.com> - 2015-12-15 19:00 +0100
      Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-15 19:30 +0100
      Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Dan Williams <dan.j.williams@intel.com> - 2015-12-15 19:30 +0100
        Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Dan Williams <dan.j.williams@intel.com> - 2015-12-15 19:40 +0100
          Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-15 19:40 +0100
            Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-15 20:30 +0100
              RE: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks "Elliott, Robert (Persistent Memory)" <elliott@hpe.com> - 2015-12-15 21:30 +0100
                Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks Borislav Petkov <bp@alien8.de> - 2015-12-21 18:40 +0100
            RE: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover  from machine checks "Elliott, Robert (Persistent Memory)" <elliott@hpe.com> - 2015-12-15 20:30 +0100

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