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 ; 07 Feb 2019 16:35:39 -0000 Received: from smtp.ctxuk.citrix.com ([185.25.65.24] helo=SMTP.EU.CITRIX.COM) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1grmeI-0006yR-8f for speck@linutronix.de; Thu, 07 Feb 2019 17:35:38 +0100 Subject: [MODERATED] Re: [PATCH v2 0/8] PERFv2 References: <20190207132709.GA32477@hirez.programming.kicks-ass.net> <20190207143759.GP31598@tassilo.jf.intel.com> <20190207153728.GE32477@hirez.programming.kicks-ass.net> From: Andrew Cooper Message-ID: <2875fb7c-1354-c401-a7e5-6cb2cb02b40c@citrix.com> Date: Thu, 7 Feb 2019 16:35:12 +0000 MIME-Version: 1.0 In-Reply-To: <20190207153728.GE32477@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable Content-Language: en-GB To: speck@linutronix.de List-ID: On 07/02/2019 15:37, speck for Peter Zijlstra wrote: > On Thu, Feb 07, 2019 at 06:37:59AM -0800, speck for Andi Kleen wrote: > >> Okay I see you rely on it being guarded by the global, but for virtualiz= ation >> support will need the copy. >> >> Would need a copy at least. > I've not thought abou virt yet; do we _have_ to expose the thing to > guests? Virt has been discussed at length. This feature and MSR are not architectural, and not expected to exist on future hardware with a silicon fix for the issue (CascadeLake B1 stepping and later, IIRC). By exposing the features to guests, you automatically limit their migrateability to a subset of the Skylake uarch processors. For Xen, I've just gone with a boot time global flag.=A0 PMU deliberately isn't available to guests in general, but developers wanting to do profiling/other can trivially flip the default. ~Andrew