From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Andy Shevchenko <andy@kernel.org>,
Mike Snitzer <msnitzer@redhat.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Mimi Zohar <zohar@linux.ibm.com>,
Milan Broz <gmazyland@gmail.com>,
device-mapper development <dm-devel@redhat.com>,
Mikulas Patocka <mpatocka@redhat.com>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Stafford Horne <shorne@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [dm-devel] [PATCH v2] hex2bin: make the function hex_to_bin constant-time
Date: Wed, 4 May 2022 12:15:31 +0200 [thread overview]
Message-ID: <YnJSQ3jJyvhmIstD@zx2c4.com> (raw)
In-Reply-To: <YnJQXr3igEMTqY3+@smile.fi.intel.com>
On Wed, May 04, 2022 at 01:07:26PM +0300, Andy Shevchenko wrote:
> On Wed, May 04, 2022 at 11:57:29AM +0200, Jason A. Donenfeld wrote:
> > On Wed, May 04, 2022 at 11:42:27AM +0200, Jason A. Donenfeld wrote:
> > > So more likely is that this patch just helps unmask a real issue
> > > elsewhere -- linker, compiler, or register restoration after preemption.
> > > I don't think there's anything to do with regards to the patch of this
> > > thread, as it's clearly fine.
> >
> > The problem even goes away if I just add a nop...
>
> Alignment? Compiler bug? HW issue?
Probably one of those, yea. Removing the instruction addresses, the only
difference between the two compiles is: https://xn--4db.cc/Rrn8usaX/diff#line-440
So either there's some alignment going on here, a compiler thing I
haven't spotted yet, or some very fragile interrupt/preemption behavior
that's interacting with this, either on the kernel side or the QEMU
side.
(I've never touched real HW for this; I just got nerd sniped when
wondering why my wireguard CI was failing...)
Jason
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WARNING: multiple messages have this Message-ID (diff)
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Stafford Horne <shorne@gmail.com>,
Mikulas Patocka <mpatocka@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Shevchenko <andy@kernel.org>,
device-mapper development <dm-devel@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Mike Snitzer <msnitzer@redhat.com>,
Mimi Zohar <zohar@linux.ibm.com>,
Milan Broz <gmazyland@gmail.com>
Subject: Re: [PATCH v2] hex2bin: make the function hex_to_bin constant-time
Date: Wed, 4 May 2022 12:15:31 +0200 [thread overview]
Message-ID: <YnJSQ3jJyvhmIstD@zx2c4.com> (raw)
In-Reply-To: <YnJQXr3igEMTqY3+@smile.fi.intel.com>
On Wed, May 04, 2022 at 01:07:26PM +0300, Andy Shevchenko wrote:
> On Wed, May 04, 2022 at 11:57:29AM +0200, Jason A. Donenfeld wrote:
> > On Wed, May 04, 2022 at 11:42:27AM +0200, Jason A. Donenfeld wrote:
> > > So more likely is that this patch just helps unmask a real issue
> > > elsewhere -- linker, compiler, or register restoration after preemption.
> > > I don't think there's anything to do with regards to the patch of this
> > > thread, as it's clearly fine.
> >
> > The problem even goes away if I just add a nop...
>
> Alignment? Compiler bug? HW issue?
Probably one of those, yea. Removing the instruction addresses, the only
difference between the two compiles is: https://xn--4db.cc/Rrn8usaX/diff#line-440
So either there's some alignment going on here, a compiler thing I
haven't spotted yet, or some very fragile interrupt/preemption behavior
that's interacting with this, either on the kernel side or the QEMU
side.
(I've never touched real HW for this; I just got nerd sniped when
wondering why my wireguard CI was failing...)
Jason
next prev parent reply other threads:[~2022-05-05 7:13 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-24 20:54 [dm-devel] [PATCH] hex2bin: make the function hex_to_bin constant-time Mikulas Patocka
2022-04-24 20:54 ` Mikulas Patocka
2022-04-24 21:30 ` [dm-devel] " Joe Perches
2022-04-24 21:30 ` Joe Perches
2022-04-24 21:37 ` [dm-devel] " Linus Torvalds
2022-04-24 21:37 ` Linus Torvalds
2022-04-24 21:42 ` [dm-devel] " Linus Torvalds
2022-04-24 21:42 ` Linus Torvalds
2022-04-25 9:37 ` [dm-devel] " David Laight
2022-04-25 9:37 ` David Laight
2022-04-25 11:04 ` [dm-devel] " Mikulas Patocka
2022-04-25 11:04 ` Mikulas Patocka
2022-04-25 12:59 ` [dm-devel] " David Laight
2022-04-25 12:59 ` David Laight
2022-04-25 13:33 ` [dm-devel] " Mikulas Patocka
2022-04-25 13:33 ` Mikulas Patocka
2022-04-25 12:07 ` [dm-devel] [PATCH v2] " Mikulas Patocka
2022-04-25 12:07 ` Mikulas Patocka
2022-04-25 17:53 ` [dm-devel] " Linus Torvalds
2022-04-25 17:53 ` Linus Torvalds
2022-05-04 8:38 ` [dm-devel] " Stafford Horne
2022-05-04 8:38 ` Stafford Horne
2022-05-04 8:57 ` [dm-devel] " Mikulas Patocka
2022-05-04 8:57 ` Mikulas Patocka
2022-05-04 9:20 ` [dm-devel] " Andy Shevchenko
2022-05-04 9:20 ` Andy Shevchenko
2022-05-04 9:47 ` [dm-devel] " Milan Broz
2022-05-04 9:47 ` Milan Broz
2022-05-04 9:50 ` [dm-devel] " Jason A. Donenfeld
2022-05-04 9:50 ` Jason A. Donenfeld
2022-05-04 11:54 ` [dm-devel] " Mikulas Patocka
2022-05-04 11:54 ` Mikulas Patocka
2022-05-04 9:42 ` [dm-devel] " Jason A. Donenfeld
2022-05-04 9:42 ` Jason A. Donenfeld
2022-05-04 9:44 ` [dm-devel] " Jason A. Donenfeld
2022-05-04 9:44 ` Jason A. Donenfeld
2022-05-04 9:57 ` [dm-devel] " Jason A. Donenfeld
2022-05-04 9:57 ` Jason A. Donenfeld
2022-05-04 10:07 ` [dm-devel] " Andy Shevchenko
2022-05-04 10:07 ` Andy Shevchenko
2022-05-04 10:15 ` Jason A. Donenfeld [this message]
2022-05-04 10:15 ` Jason A. Donenfeld
2022-05-04 18:00 ` [dm-devel] " Linus Torvalds
2022-05-04 18:00 ` Linus Torvalds
2022-05-04 19:42 ` [dm-devel] " Jason A. Donenfeld
2022-05-04 19:42 ` Jason A. Donenfeld
2022-05-04 19:51 ` [dm-devel] " Linus Torvalds
2022-05-04 19:51 ` Linus Torvalds
2022-05-04 20:00 ` [dm-devel] " Linus Torvalds
2022-05-04 20:00 ` Linus Torvalds
2022-05-04 20:12 ` [dm-devel] " Stafford Horne
2022-05-04 20:12 ` Stafford Horne
2022-05-04 20:26 ` [dm-devel] " Linus Torvalds
2022-05-04 20:26 ` Linus Torvalds
2022-05-04 21:24 ` [dm-devel] " Linus Torvalds
2022-05-04 21:24 ` Linus Torvalds
2022-05-04 19:57 ` [dm-devel] " Stafford Horne
2022-05-04 19:57 ` Stafford Horne
2022-05-04 20:10 ` [dm-devel] " Linus Torvalds
2022-05-04 20:10 ` Linus Torvalds
2022-05-04 20:38 ` [dm-devel] " Stafford Horne
2022-05-04 20:38 ` Stafford Horne
2022-05-08 0:37 ` [dm-devel] " Stafford Horne
2022-05-08 0:37 ` Stafford Horne
2022-05-11 12:17 ` [dm-devel] " Stafford Horne
2022-05-11 12:17 ` Stafford Horne
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