From: Andi Kleen <ak@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Hansen <dave.hansen@intel.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM
Date: Thu, 23 Aug 2018 15:07:53 -0700 [thread overview]
Message-ID: <20180823220753.GG12066@tassilo.jf.intel.com> (raw)
In-Reply-To: <20180823200520.GW29735@dhcp22.suse.cz>
On Thu, Aug 23, 2018 at 10:05:20PM +0200, Michal Hocko wrote:
> On Thu 23-08-18 12:38:33, Andi Kleen wrote:
> > > There are people who care about L1TF mitigations. I am not going to
> > > question their motivation. In any case a hint how to make the mitigation
> > > active again sounds more useful than something that sounds as scary as
> > > "you are vulnerable".
> >
> > FWIW an early version of these patches automatically limited the available
> > memory, but Linus pointed out that people likely prefer their memory.
>
> Nobody is questioning that. The point is to give them a hint on how to
> make the mitigation active again without going to call for help. The
> message does tell them how to _enable_ it and point them to the
> documentation on how to _decide_.
On the message I guess there are two cases:
- either it's very little memory that is lost like in the 32GB + memory
hole case. In this case maybe it's better if we just limit automatically
if the overlap is small enough (<2GB perhaps?)
- Or it's a lot of memory then people are unlikely to want to lose their
memory and I don't think we really need the message either.
Also I checked the bug again and it looks like the reporter has an IvyBridge.
There is actually a better solution for those (anything Nehalem and newer)
because they internally have at least 44 bits in the cache, which
is good enough for the mitigation. Just need a quirk to override
the bit width in this case (will submit a patch)
-Andi
next prev parent reply other threads:[~2018-08-23 22:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 13:44 [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has too much RAM Vlastimil Babka
2018-08-23 13:56 ` Michal Hocko
2018-08-23 14:28 ` [PATCH] x86/speculation/l1tf: suggest what to do on systems with " Vlastimil Babka
2018-08-23 15:46 ` Andi Kleen
2018-08-23 19:25 ` Michal Hocko
2018-08-23 19:38 ` Andi Kleen
2018-08-23 20:05 ` Michal Hocko
2018-08-23 22:07 ` Andi Kleen [this message]
2018-08-23 19:03 ` kbuild test robot
2018-08-23 19:23 ` kbuild test robot
2018-08-23 19:27 ` Michal Hocko
2018-08-24 7:32 ` Vlastimil Babka
2018-08-24 7:55 ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka
2018-08-24 10:36 ` [PATCH] x86/speculation/l1tf: suggest " Vlastimil Babka
2018-08-24 12:10 ` Vlastimil Babka
2018-08-24 12:20 ` Michal Hocko
2018-08-24 13:57 ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka
2018-08-23 15:44 ` [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has " Andi Kleen
2018-08-23 20:20 ` Vlastimil Babka
2018-08-24 2:22 ` Andre Tomt
2018-08-24 3:35 ` Andi Kleen
2018-08-29 2:04 ` Christopher Snowhill
2018-08-24 8:52 ` xxxxxx xxxxxx
2018-08-24 7:55 ` [tip:x86/urgent] x86/speculation/l1tf: Fix " tip-bot for Vlastimil Babka
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