From: Jon Masters <jcm@jonmasters.org>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
Andi Kleen <andi@firstfloor.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org,
pjt@google.com, torvalds@linux-foundation.org,
gregkh@linux-foundation.org, peterz@infradead.org,
luto@amacapital.net, thomas.lendacky@amd.com,
arjan.van.de.ven@intel.com
Subject: Re: Improve retpoline for Skylake
Date: Mon, 15 Jan 2018 03:26:34 -0500 [thread overview]
Message-ID: <985f979e-0740-5d8a-d6b8-b023105aa021@jonmasters.org> (raw)
In-Reply-To: <20180112220349.7dorb3lde4tffsjm@khazad-dum.debian.net>
On 01/12/2018 05:03 PM, Henrique de Moraes Holschuh wrote:
> On Fri, 12 Jan 2018, Andi Kleen wrote:
>>> Skylake still loses if it takes an SMI, right?
>>
>> SMMs are usually rare, especially on servers, and are usually
>> not very predictible, and even if you have
>
> FWIW, a data point: SMIs can be generated on demand by userspace on
> thinkpad laptops, but they will be triggered from within a kernel
> context. I very much doubt this is a rare pattern...
Sure. Just touch some "legacy" hardware that the vendor emulates in a
nasty SMI handler. It's definitely not acceptable to assume that SMIs
can't be generated under the control of some malicious user code.
Our numbers on Skylake weren't bad, and there seem to be all kinds of
corner cases, so again, it seems as if IBRS is the safest choice.
Jon.
next prev parent reply other threads:[~2018-01-15 8:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 18:45 Andi Kleen
2018-01-12 18:45 ` [PATCH 1/4] x86/retpoline: Add new mode RETPOLINE_UNDERFLOW Andi Kleen
2018-01-12 22:13 ` Dominik Brodowski
2018-01-12 22:57 ` Andi Kleen
2018-01-12 18:45 ` [PATCH 2/4] x86/retpoline: Avoid return buffer underflows on context switch Andi Kleen
2018-01-12 18:45 ` [PATCH 3/4] x86/retpoline: Fill return buffer after idle Andi Kleen
2018-01-12 18:45 ` [PATCH 4/4] x86/retpoline: Fill return buffer on interrupt return to kernel Andi Kleen
2018-01-12 19:12 ` Improve retpoline for Skylake David Woodhouse
2018-01-12 19:21 ` Andi Kleen
2018-01-12 22:03 ` Henrique de Moraes Holschuh
2018-01-15 8:26 ` Jon Masters [this message]
2018-01-15 9:06 ` David Woodhouse
2018-01-15 10:03 ` Thomas Gleixner
2018-01-15 10:20 ` David Woodhouse
2018-01-15 16:57 ` Andy Lutomirski
2018-01-15 17:38 ` Andrew Cooper
2018-01-15 17:56 ` Van De Ven, Arjan
2018-01-15 18:06 ` Andy Lutomirski
2018-01-15 18:07 ` David Woodhouse
2018-01-15 18:10 ` Andy Lutomirski
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