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 ; 23 Feb 2019 09:52:39 -0000 Received: from mail.kernel.org ([198.145.29.99]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gxTz3-0006Hr-TE for speck@linutronix.de; Sat, 23 Feb 2019 10:52:38 +0100 Date: Sat, 23 Feb 2019 10:52:28 +0100 From: Greg KH Subject: [MODERATED] Re: [patch V4 09/11] x86/speculation/mds: Add mitigation mode VMWERV Message-ID: <20190223095228.GB11354@kroah.com> References: <20190222222418.405369026@linutronix.de> <20190222224149.881444221@linutronix.de> MIME-Version: 1.0 In-Reply-To: <20190222224149.881444221@linutronix.de> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: 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 > > Signed-off-by: Thomas Gleixner Thanks for the documentation update here, looks good. Reviewed-by: Greg Kroah-Hartman