linux-kernel - Re: [RFC PATCH v3] sparc64: Add support for Application Data Integrity (ADI)

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Message-ID: <20170106091934.GF5556@dhcp22.suse.cz>
Date:   Fri, 6 Jan 2017 10:19:34 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Khalid Aziz <khalid.aziz@...cle.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Rob Gardner <rob.gardner@...cle.com>, davem@...emloft.net,
        corbet@....net, arnd@...db.de, akpm@...ux-foundation.org,
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        adam.buchbinder@...il.com, minchan@...nel.org, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, keescook@...omium.org,
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        iamjoonsoo.kim@....com, mgorman@...hsingularity.net,
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        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
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        x86@...nel.org, linux-mm@...ck.org,
        Khalid Aziz <khalid@...ehiking.org>
Subject: Re: [RFC PATCH v3] sparc64: Add support for Application Data
 Integrity (ADI)

On Thu 05-01-17 13:30:10, Khalid Aziz wrote:
[...]
> It is very tempting to restrict tags to PAGE_SIZE granularity since it makes
> code noticeably simpler and that is indeed going to be the majority of
> cases. Sooner or later somebody would want to use multiple tags per page
> though.

I didn't get to read the patch throughly yet but I am really confused by
this statement. The api is mprotect based which makes it ineherently
PAGE_SIZE granular. How do you want to achieve cache line granularity
with this API?

And I would really vote for simplicity first... Subpage granularity
sounds way too tricky...
-- 
Michal Hocko
SUSE Labs