Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965340AbeALWDz (ORCPT + 1 other); Fri, 12 Jan 2018 17:03:55 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:43107 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965220AbeALWDx (ORCPT ); Fri, 12 Jan 2018 17:03:53 -0500 X-ME-Sender: Date: Fri, 12 Jan 2018 20:03:49 -0200 From: Henrique de Moraes Holschuh To: Andi Kleen Cc: David Woodhouse , 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 Message-ID: <20180112220349.7dorb3lde4tffsjm@khazad-dum.debian.net> References: <20180112184550.6573-1-andi@firstfloor.org> <1515784373.22302.492.camel@infradead.org> <20180112192126.su2evwfefdfeaa6g@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180112192126.su2evwfefdfeaa6g@two.firstfloor.org> X-GPG-Fingerprint1: 4096R/0x0BD9E81139CB4807: C467 A717 507B BAFE D3C1 6092 0BD9 E811 39CB 4807 User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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... However, since in this vendor-firmware-nastyness pattern the SMIs are fired off from inside the kernel (inside the ACPI subsystem), it would be covered by the mitigations done when entering the kernel from syscalls and hardware interrupts. Hopefully. -- Henrique Holschuh