From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave@sr71.net>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
dave.hansen@linux.intel.com
Subject: Re: [PATCH 17/19] x86, mpx: rewrite unmap code
Date: Mon, 18 May 2015 23:55:24 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1505182354430.4225@nanos> (raw)
In-Reply-To: <20150508185957.C657301B@viggo.jf.intel.com>
On Fri, 8 May 2015, Dave Hansen wrote:
> The MPX code needs to clear out bounds tables for memory which
> is no longer in use. We do this when a userspace mapping is
> torn down (unmapped).
>
> There are two modes:
> 1. An entire bounds table becomes unused, and can be freed
> and its pointer removed from the bounds directory. This
> happens either when a large mapping is torn down, or when
> a small mapping is torn down and it is the last mapping
> "covered" by a bounds table.
> 2. Only part of a bounds table becomes unused, in which case
> we free the backing memory as if MADV_DONTNEED was called.
>
> The old code was a spaghetti mess of "edge" bounds tables
> where the edges were handled specially, even if we were
> unmapping an entire one. Non-edge bounds tables are always
> fully unmapped, but share a different code path from the edge
> ones. The old code had a bug where it was unmapping too much
> memory. I worked on fixing it for two days and gave up.
>
> I didn't write the original code. I didn't particularly like
> it, but it worked, so I left it. After my debug session, I
> realized it was undebuggagle *and* buggy, so out it went.
>
> I also wrote a new unmapping test program which uncovers bugs
> pretty nicely.
Very appreciated. This is really readable now.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2015-05-18 21:55 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-08 18:59 [PATCH 00/19] x86, mpx updates for 4.2 (take 6) Dave Hansen
2015-05-08 18:59 ` [PATCH 01/19] x86, mpx, xsave: fix up bad get_xsave_addr() assumptions Dave Hansen
2015-05-18 19:34 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 02/19] x86, fpu: wrap get_xsave_addr() to make it safer Dave Hansen
2015-05-18 19:38 ` Thomas Gleixner
2015-05-18 19:42 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 03/19] x86, mpx: use new tsk_get_xsave_addr() Dave Hansen
2015-05-18 20:36 ` Thomas Gleixner
2015-05-19 0:01 ` Dave Hansen
2015-05-08 18:59 ` [PATCH 04/19] x86, mpx: cleanup: do not pass task around when unnecessary Dave Hansen
2015-05-18 20:38 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 05/19] x86, mpx: remove redundant MPX_BNDCFG_ADDR_MASK Dave Hansen
2015-05-18 20:38 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 06/19] x86, mpx: we do not allocate the bounds directory Dave Hansen
2015-05-18 20:43 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 07/19] x86, mpx: boot-time disable Dave Hansen
2015-05-18 20:45 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 08/19] x86, mpx: trace #BR exceptions Dave Hansen
2015-05-18 21:00 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 10/19] x86, mpx: trace ranged MPX operations Dave Hansen
2015-05-18 21:04 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 09/19] x86, mpx: trace entry to bounds exception paths Dave Hansen
2015-05-18 20:58 ` Thomas Gleixner
2015-05-18 23:06 ` Dave Hansen
2015-05-18 23:35 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 11/19] x86, mpx: trace allocation of new bounds tables Dave Hansen
2015-05-18 21:04 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 12/19] x86: make is_64bit_mm() widely available Dave Hansen
2015-05-18 21:06 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 14/19] x86, mpx: new directory entry to addr helper Dave Hansen
2015-05-18 21:10 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 13/19] x86, mpx: Add temporary variable to reduce masking Dave Hansen
2015-05-18 21:07 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 15/19] x86, mpx: do 32-bit-only cmpxchg for 32-bit apps Dave Hansen
2015-05-18 21:22 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 16/19] x86, mpx: support 32-bit binaries on 64-bit kernel Dave Hansen
2015-05-18 21:53 ` Thomas Gleixner
2015-05-18 23:29 ` Dave Hansen
2015-05-18 23:37 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 17/19] x86, mpx: rewrite unmap code Dave Hansen
2015-05-18 21:55 ` Thomas Gleixner [this message]
2015-05-08 18:59 ` [PATCH 18/19] x86, mpx: do not count MPX VMAs as neighbors when unmapping Dave Hansen
2015-05-18 21:54 ` Thomas Gleixner
2015-05-08 18:59 ` [PATCH 19/19] x86, mpx: allow mixed binaries again Dave Hansen
2015-05-18 21:55 ` Thomas Gleixner
2015-05-19 6:25 [PATCH 00/19] x86, mpx updates for 4.2 (take 7) Dave Hansen
2015-05-19 6:25 ` [PATCH 17/19] x86, mpx: rewrite unmap code Dave Hansen
2015-05-27 18:36 [PATCH 00/19] x86, mpx updates for 4.2 (take 8) Dave Hansen
2015-05-27 18:36 ` [PATCH 17/19] x86, mpx: rewrite unmap code Dave Hansen
2015-06-07 18:37 [PATCH 00/19] x86, mpx updates for 4.2 (take 9) Dave Hansen
2015-06-07 18:37 ` [PATCH 17/19] x86, mpx: rewrite unmap code Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.11.1505182354430.4225@nanos \
--to=tglx@linutronix.de \
--cc=dave.hansen@linux.intel.com \
--cc=dave@sr71.net \
--cc=linux-kernel@vger.kernel.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).