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From: Andrei Vagin <avagin@gmail.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	dima@arista.com, arnd@arndb.de, tglx@linutronix.de,
	vincenzo.frascino@arm.com, luto@kernel.org,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH RESEND v1 3/4] powerpc/vdso: Separate vvar vma from vdso
Date: Sun, 4 Apr 2021 22:03:37 -0700	[thread overview]
Message-ID: <YGqaKYnLnvj2brJ8@gmail.com> (raw)
In-Reply-To: <f401eb1ebc0bfc4d8f0e10dc8e525fd409eb68e2.1617209142.git.christophe.leroy@csgroup.eu>

On Wed, Mar 31, 2021 at 04:48:46PM +0000, Christophe Leroy wrote:
> From: Dmitry Safonov <dima@arista.com>
> 
> Since commit 511157ab641e ("powerpc/vdso: Move vdso datapage up front")
> VVAR page is in front of the VDSO area. In result it breaks CRIU
> (Checkpoint Restore In Userspace) [1], where CRIU expects that "[vdso]"
> from /proc/../maps points at ELF/vdso image, rather than at VVAR data page.
> Laurent made a patch to keep CRIU working (by reading aux vector).
> But I think it still makes sence to separate two mappings into different
> VMAs. It will also make ppc64 less "special" for userspace and as
> a side-bonus will make VVAR page un-writable by debugger (which previously
> would COW page and can be unexpected).
> 
> I opportunistically Cc stable on it: I understand that usually such
> stuff isn't a stable material, but that will allow us in CRIU have
> one workaround less that is needed just for one release (v5.11) on
> one platform (ppc64), which we otherwise have to maintain.
> I wouldn't go as far as to say that the commit 511157ab641e is ABI
> regression as no other userspace got broken, but I'd really appreciate
> if it gets backported to v5.11 after v5.12 is released, so as not
> to complicate already non-simple CRIU-vdso code. Thanks!
> 
> Cc: Andrei Vagin <avagin@gmail.com>

Acked-by: Andrei Vagin <avagin@gmail.com>

> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: Laurent Dufour <ldufour@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: stable@vger.kernel.org # v5.11
> [1]: https://github.com/checkpoint-restore/criu/issues/1417
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

  reply	other threads:[~2021-04-05  5:06 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-31 16:48 [PATCH RESEND v1 0/4] powerpc/vdso: Add support for time namespaces Christophe Leroy
2021-03-31 16:48 ` [PATCH RESEND v1 1/4] lib/vdso: Mark do_hres_timens() and do_coarse_timens() __always_inline() Christophe Leroy
2021-04-12 12:47   ` Thomas Gleixner
2021-04-12 12:54   ` Vincenzo Frascino
2021-03-31 16:48 ` [PATCH RESEND v1 2/4] lib/vdso: Add vdso_data pointer as input to __arch_get_timens_vdso_data() Christophe Leroy
2021-04-05  5:00   ` Andrei Vagin
2021-04-12 12:48   ` Thomas Gleixner
2021-04-12 12:56   ` Vincenzo Frascino
2021-03-31 16:48 ` [PATCH RESEND v1 3/4] powerpc/vdso: Separate vvar vma from vdso Christophe Leroy
2021-04-05  5:03   ` Andrei Vagin [this message]
2021-04-12 12:58   ` Vincenzo Frascino
2021-03-31 16:48 ` [PATCH RESEND v1 4/4] powerpc/vdso: Add support for time namespaces Christophe Leroy
2021-04-05  4:50   ` Andrei Vagin
2021-04-12 13:00   ` Vincenzo Frascino
2021-04-12 12:49 ` [PATCH RESEND v1 0/4] " Thomas Gleixner
2021-04-13  6:31   ` Michael Ellerman
2021-04-19  4:00 ` Michael Ellerman

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