linux-kernel - Re: [PATCH v15 07/26] x86/mm: Remove _PAGE_DIRTY

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Message-ID: <20201207163632.GE20489@zn.tnic>
Date:   Mon, 7 Dec 2020 17:36:32 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v15 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO
 pages

On Tue, Nov 10, 2020 at 08:21:52AM -0800, Yu-cheng Yu wrote:
> Kernel read-only PTEs are setup as _PAGE_DIRTY_HW.  Since these become
> shadow stack PTEs, remove the dirty bit.

This commit message is laconic to say the least. You need to start
explaining what you're doing because everytime I look at a patch of
yours, I'm always grepping the SDM and looking forward in the patchset,
trying to rhyme up what that is all about.

Like for this one. I had to fast-forward to the next patch where all
that is explained. But this is not how review works - each patch's
commit message needs to be understandable on its own because when
they land upstream, they're not in a patchset like here. And review
should be done in the order the patches are numbered - not by jumping
back'n'forth.

So please think of the readers of your patches when writing those commit
messages. Latter are *not* write-only and not unimportant.

And those readers haven't spent copious amounts of time on the
technology so being more verbose and explaining things is a Good
Thing(tm). Don't worry about explaining too much - better too much than
too little.

And last but not least, having understandable and properly written
commit messages increases the chances of your patches landing upstream
considerably.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette