RE: [PATCH] x86: only use ERMS for user copies for larger sizes

[David Laight]

From: Linus Torvalds
> Sent: 23 November 2018 16:36
...
> End result: we *used* to do this right. For the last eight years our
> "memcpy_{to,from}io()" has been entirely broken, and apparently even
> the people who noticed oddities like David, never reported it as
> breakage but instead just worked around it in drivers.

I've mentioned it several times...

Probably no one else noticed lots of single byte transfers while
testing a TLP monitor he was writing for an FPGA :-)
They are far too expensive to buy, and would never be connected
to the right system at the right time - so we (I) wrote one.

Unfortunately we don't really get to see what happens when the
link comes up (or rather doesn't come up). We only get the
LTSSM state transitions.

	David

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