From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (146.0.238.70:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 26 Feb 2019 19:29:39 -0000 Received: from p5492e0d8.dip0.t-ipconnect.de ([84.146.224.216] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gyiQ6-0000Zm-9V for speck@linutronix.de; Tue, 26 Feb 2019 20:29:38 +0100 Date: Tue, 26 Feb 2019 20:29:32 +0100 (CET) From: Thomas Gleixner Subject: Re: [patch V4 09/11] x86/speculation/mds: Add mitigation mode VMWERV In-Reply-To: <20190225203101.GB6558@mgross-MOBL.amr.corp.intel.com> Message-ID: References: <20190222222418.405369026@linutronix.de> <20190222224149.881444221@linutronix.de> <20190225203101.GB6558@mgross-MOBL.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: On Mon, 25 Feb 2019, speck for mark gross wrote: > On Fri, Feb 22, 2019 at 11:24:27PM +0100, speck for Thomas Gleixner wrote: > > From: Thomas Gleixner > > > > In virtualized environments it can happen that the host has the microcode > > update which utilizes the VERW instruction to clear CPU buffers, but the > > hypervisor is not yet updated to expose the X86_FEATURE_MD_CLEAR CPUID bit > > to guests. > > > > Introduce an internal mitigation mode VWWERV which enables the invocation > > of the CPU buffer clearing even if X86_FEATURE_MD_CLEAR is not set. If the > > system has no updated microcode this results in a pointless execution of > > the VERW instruction wasting a few CPU cycles. If the microcode is updated, > > but not exposed to a guest then the CPU buffers will be cleared. > > > > That said: Virtual Machines Will Eventually Receive Vaccine > > + vmwerv Mitigation is enabled. CPU is affected and MD_CLEAR is not > vmverw <-- type oh? Actually it's intentional. I was looking for something which is a subtle hint for why this thing exists in the first place and is a proper acronym. See above. I probably could come up with something for what vmverw states, but the subtle hint is then even more subtle. Not that I care much. Thanks, tglx