Re: [PATCH v8 3/3] x86, mce: Add __mcsafe_copy()

[Dan Williams]

On Sat, Jan 9, 2016 at 2:33 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Sat, Jan 9, 2016 at 2:15 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>> On Sat, Jan 9, 2016 at 11:39 AM, Tony Luck <tony.luck@xxxxxxxxx> wrote:
>>> On Sat, Jan 9, 2016 at 9:57 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>>> On Sat, Jan 9, 2016 at 9:48 AM, Tony Luck <tony.luck@xxxxxxxxx> wrote:
>>>>> ERMS?
>>>>
>>>> It's the fast string extension, aka Enhanced REP MOV STOS.  On CPUs
>>>> with that feature (and not disabled via MSR), plain ol' rep movs is
>>>> the fastest way to copy bytes.  I think this includes all Intel CPUs
>>>> from SNB onwards.
>>>
>>> Ah ... very fast at copying .. but currently not machine check recoverable.
>>
>> Hmm, I assume for the pmem driver I'll want to check at runtime if the
>> cpu has machine check recovery and fall back to the faster copy if
>> it's not available?
>
> Shouldn't that logic live in the mcsafe_copy routine itself rather
> than being delegated to callers?
>

Yes, please.