Re: [PATCH 5/8] x86/mce: Avoid tail copy when machine check terminated a copy from user

[Luck, Tony]

On Thu, Sep 17, 2020 at 07:04:06PM +0200, Borislav Petkov wrote:
> So actually, I'm thinking:
> 
> .LMCE_during_user_access:
> 	mov $-ENODEV, %eax
> 	ASM_CLAC
> 	ret
> 
> I have no clue which error code we should put there but it should be an
> error code which tells you not to retry and to back off immediately.

That does look a lot easier to understand *at this point* in the code.

But the existing iterator code is not expecting an error code.  Just a
count of bytes not copied.

So doing this would mean some surgery on the maze of giant #defines that
is lib/iov_iter.c

-Tony