linux-kernel - Re: [PATCH v11 3/4] x86, mce: Add __mcsafe

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Message-ID: <20160218101942.GA9386@gmail.com>
Date:	Thu, 18 Feb 2016 11:19:42 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy()


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Thu, Feb 18, 2016 at 09:21:07AM +0100, Ingo Molnar wrote:
> > 
> > * Tony Luck <tony.luck@...el.com> wrote:
> > 
> > > Make use of the EXTABLE_FAULT exception table entries. This routine
> > > returns a structure to indicate the result of the copy:
> > 
> > So the series looks good to me, but I have some (mostly readability) comments that 
> > went beyond what I usually fix up manually:
> > 
> > > struct mcsafe_ret {
> > >         u64 trapnr;
> > >         u64 remain;
> > > };
> > 
> > > +struct mcsafe_ret {
> > > +	u64 trapnr;
> > > +	u64 remain;
> > > +};
> > 
> > Yeah, so please change this to something like:
> > 
> >   struct mcsafe_ret {
> >           u64 trap_nr;
> >           u64 bytes_left;
> >   };
> > 
> > this makes it crystal clear what the fields are about and what their unit is. 
> > Readability is king and modern consoles are wide enough, no need to abbreviate 
> > excessively.
> 
> I prefer to use my modern console width to display multiple columns of
> text, instead of wasting it to display mostly whitespace. Therefore I
> still very much prefer ~80 char wide code.

This naming won't hurt the col80 limit.

> > Also, I'd suggest we postfix the new mcsafe functions with '_mcsafe', not 
> > prefix them. Special properties of memcpy routines are usually postfixes - 
> > such as _nocache(), _toio(), etc.
> 
> I think the whole notion of mcsafe here is 'wrong'. This copy variant simply 
> reports the kind of trap that happened (#PF or #MC) and could arguably be 
> extended to include more types if the hardware were to generate more.

What would a better name be? memcpy_ret() or so?

Thanks,

	Ingo