From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 0D5E83854835; Thu, 18 Mar 2021 17:45:20 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 0D5E83854835
From: "dj at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/27605] New: tunables can't control xsave/xsavec selection
 in dl_runtime_resolve_*
Date: Thu, 18 Mar 2021 17:45:19 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: glibc
X-Bugzilla-Component: libc
X-Bugzilla-Version: 2.34
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: dj at redhat dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter cc target_milestone
Message-ID: <bug-27605-131@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: glibc-bugs@sourceware.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Glibc-bugs mailing list <glibc-bugs.sourceware.org>
List-Unsubscribe: <https://sourceware.org/mailman/options/glibc-bugs>,
 <mailto:glibc-bugs-request@sourceware.org?subject=unsubscribe>
List-Archive: <https://sourceware.org/pipermail/glibc-bugs/>
List-Help: <mailto:glibc-bugs-request@sourceware.org?subject=help>
List-Subscribe: <https://sourceware.org/mailman/listinfo/glibc-bugs>,
 <mailto:glibc-bugs-request@sourceware.org?subject=subscribe>
X-List-Received-Date: Thu, 18 Mar 2021 17:45:20 -0000

https://sourceware.org/bugzilla/show_bug.cgi?id=3D27605

            Bug ID: 27605
           Summary: tunables can't control xsave/xsavec selection in
                    dl_runtime_resolve_*
           Product: glibc
           Version: 2.34
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: dj at redhat dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

in sysdeps/x86/cpu-features.c, the decision to use xsave/xsavec is made -
indirectly, by computing the save set size - before the tunables have a cha=
nce
to affect it.  The logic in update_usable() should be deferred until after =
the
tunables check in init_cpu_features().  As it is, you can't control which
_dl_runtime_resolve_* ifunc is used, by disabling xsave/osxsave in tunables.

See: https://sourceware.org/pipermail/libc-alpha/2021-March/124133.html
See: https://bugzilla.redhat.com/show_bug.cgi?id=3D1937515

The desired result allows for a process to be migrated from a with-xsave
machine to a without-xsave machine, or across different with-xsavec machine=
s,
by disabling all xsave/xsavec (with the usual caveats about not using exten=
ded
registers) completely.

--=20
You are receiving this mail because:
You are on the CC list for the bug.=