From: Ralf Baechle <ralf@linux-mips.org>
To: linux-mips@linux-mips.org
Subject: Warning about add_wired_entry
Date: Mon, 7 Dec 2009 15:02:36 +0000 [thread overview]
Message-ID: <20091207150236.GD19269@linux-mips.org> (raw)
The earlier posting wrt. add_wired_entry reminded my of this long standing
issue.
The kernel does not reserve any address space for use by add_wired_entry().
In other words there is the possibility that vmalloc, ioremap or other
kernel APIs will use the same address space resulting in a crash or worse.
Currently there are three users of add_wired_entry:
- Alchemy
- Cavium
- Jazz
The interface itself also is hostile as it directly exposes the MIPS TLB
registers to the C programmer so should die. And often wiring a TLB entry
is a bad idea. TLB entries are a scarce resource and wasting them unwisely
may impact performance. Especially on the lowest-end CPUs with just
16 TLB entries this can be significant but even on the high-end TLBs with
64 entries it's not always clear if wiring entries is a good idea. And
there are a few core types that don't even have the capability of wiring
entries.
Ralf
next reply other threads:[~2009-12-07 15:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-07 15:02 Ralf Baechle [this message]
2009-12-07 15:41 ` Warning about add_wired_entry pascal
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=20091207150236.GD19269@linux-mips.org \
--to=ralf@linux-mips.org \
--cc=linux-mips@linux-mips.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.