linux-kernel - Re: [PATCH v10 11/12] x86, mm, pat: Refactor !pat

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 29 May 2015 10:58:42 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@...com>
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, arnd@...db.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-nvdimm@...ts.01.org, jgross@...e.com,
	stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br,
	yigal@...xistor.com, konrad.wilk@...cle.com, Elliott@...com,
	mcgrof@...e.com, hch@....de
Subject: Re: [PATCH v10 11/12] x86, mm, pat: Refactor !pat_enabled handling

On Wed, May 27, 2015 at 09:19:03AM -0600, Toshi Kani wrote:
> This patch refactors the !pat_enabled code paths and integrates

Please refrain from using such empty phrases like "This patch does this
and that" in your commit messages - it is implicitly obvious that it is
"this patch" when one reads it.

> them into the PAT abstraction code.  The PAT table is emulated by
> corresponding to the two cache attribute bits, PWT (Write Through)
> and PCD (Cache Disable).  The emulated PAT table is the same as the
> BIOS default setup when the system has PAT but the "nopat" boot
> option is specified.  The emulated PAT table is also used when
> MSR_IA32_CR_PAT returns 0 (9d34cfdf4).

9d34cfdf4 - what is that thing? A commit message? If so, we quote them
like this:

  9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly")

note the 12 chars length of the commit id.

> Signed-off-by: Toshi Kani <toshi.kani@...com>
> Reviewed-by: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/mm/init.c     |    6 ++--
>  arch/x86/mm/iomap_32.c |   12 ++++---
>  arch/x86/mm/ioremap.c  |   10 +-----
>  arch/x86/mm/pageattr.c |    6 ----
>  arch/x86/mm/pat.c      |   77 +++++++++++++++++++++++++++++-------------------
>  5 files changed, 57 insertions(+), 54 deletions(-)

So I started applying your pile and everything was ok-ish until I came
about this trainwreck. You have a lot of changes in here, the commit
message is certainly lacking sufficient explanation as to why and this
patch is changing stuff which the previous one adds.

So a lot of unnecesary code movement.

Then you have stuff like this:

	+       } else if (!cpu_has_pat && pat_enabled) {

How can a CPU not have PAT but have it enabled?!?

So this is not how we do patchsets.

Please do the cleanups *first*. Do them in small, self-contained changes
explaining *why* you're doing them.

*Then* add the new functionality, .i.e. the WT.

Oh, and when you do your next version, do the patches against tip/master
because there are a bunch of changes in the PAT code already.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/