From: Florian Weimer <fweimer@redhat.com>
To: Ram Pai <linuxram@us.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
linux-api@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-mm@kvack.org
Subject: Re: pkeys: Reserve PKEY_DISABLE_READ
Date: Mon, 03 Dec 2018 16:52:02 +0100 [thread overview]
Message-ID: <87pnuibobh.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <20181203040249.GA11930@ram.oc3035372033.ibm.com> (Ram Pai's message of "Sun, 2 Dec 2018 20:02:49 -0800")
* Ram Pai:
> So the problem is as follows:
>
> Currently the kernel supports 'disable-write' and 'disable-access'.
>
> On x86, cpu supports 'disable-write' and 'disable-access'. This
> matches with what the kernel supports. All good.
>
> However on power, cpu supports 'disable-read' too. Since userspace can
> program the cpu directly, userspace has the ability to set
> 'disable-read' too. This can lead to inconsistency between the kernel
> and the userspace.
>
> We want the kernel to match userspace on all architectures.
Correct.
> Proposed Solution:
>
> Enhance the kernel to understand 'disable-read', and facilitate architectures
> that understand 'disable-read' to allow it.
>
> Also explicitly define the semantics of disable-access as
> 'disable-read and disable-write'
>
> Did I get this right? Assuming I did, the implementation has to do
> the following --
>
> On power, sys_pkey_alloc() should succeed if the init_val
> is PKEY_DISABLE_READ, PKEY_DISABLE_WRITE, PKEY_DISABLE_ACCESS
> or any combination of the three.
Agreed.
> On x86, sys_pkey_alloc() should succeed if the init_val is
> PKEY_DISABLE_WRITE or PKEY_DISABLE_ACCESS or PKEY_DISABLE_READ
> or any combination of the three, except PKEY_DISABLE_READ
> specified all by itself.
Again agreed. That's a clever way of phrasing it actually.
> On all other arches, none of the flags are supported.
>
>
> Are we on the same plate?
I think so, thanks.
Florian
next prev parent reply other threads:[~2018-12-03 16:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <877ehnbwqy.fsf@oldenburg.str.redhat.com>
2018-11-08 19:22 ` pkeys: Reserve PKEY_DISABLE_READ Ram Pai
2018-11-12 10:29 ` Florian Weimer
[not found] ` <2d62c9e2-375b-2791-32ce-fdaa7e7664fd@intel.com>
[not found] ` <87bm6zaa04.fsf@oldenburg.str.redhat.com>
[not found] ` <6f9c65fb-ea7e-8217-a4cc-f93e766ed9bb@intel.com>
[not found] ` <87k1ln8o7u.fsf@oldenburg.str.redhat.com>
2018-11-08 20:12 ` Ram Pai
2018-11-08 20:23 ` Florian Weimer
2018-11-09 18:09 ` Ram Pai
2018-11-12 12:00 ` Florian Weimer
2018-11-27 10:23 ` Ram Pai
2018-11-27 11:57 ` Florian Weimer
2018-11-27 15:31 ` Dave Hansen
2018-11-29 11:37 ` Florian Weimer
2018-12-03 4:02 ` Ram Pai
2018-12-03 15:52 ` Florian Weimer [this message]
2018-12-04 6:23 ` Ram Pai
2018-12-05 13:00 ` Florian Weimer
2018-12-05 20:23 ` Ram Pai
2018-12-05 16:21 ` Andy Lutomirski
2018-12-05 20:36 ` Ram Pai
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=87pnuibobh.fsf@oldenburg.str.redhat.com \
--to=fweimer@redhat.com \
--cc=dave.hansen@intel.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=linuxram@us.ibm.com \
/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).