From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH v6 18/29] xen/x86: allow disabling the emulated pmu Date: Fri, 25 Sep 2015 11:41:22 -0400 Message-ID: <56056B22.2010506@oracle.com> References: <1441368548-43465-1-git-send-email-roger.pau@citrix.com> <1441368548-43465-19-git-send-email-roger.pau@citrix.com> <560031F602000078000A4186@prv-mh.provo.novell.com> <560018C7.9040004@oracle.com> <5605633C.8000708@citrix.com> <560580C702000078000A5B2A@prv-mh.provo.novell.com> <560566B8.2020803@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZfV9K-0008Lb-W6 for xen-devel@lists.xenproject.org; Fri, 25 Sep 2015 15:43:03 +0000 In-Reply-To: <560566B8.2020803@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: =?windows-1252?Q?Roger_Pau_Monn=E9?= , Jan Beulich Cc: Andrew Cooper , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On 09/25/2015 11:22 AM, Roger Pau Monn=E9 wrote: > El 25/09/15 a les 17.13, Jan Beulich ha escrit: >>>>> On 25.09.15 at 17:07, wrote: >>> El 21/09/15 a les 16.48, Boris Ostrovsky ha escrit: >>>> On 09/21/2015 10:36 AM, Jan Beulich wrote: >>>>>>>> On 04.09.15 at 14:08, wrote: >>>>> Hmm - this seems questionable to me: Isn't the vPMU an optional >>>>> feature anyway? I.e. doesn't need separate handling here? Boris? >>>> It is optional system-wise, not per-guest, which is what I think Roger >>>> is trying to do. I in fact wanted to add ability to disable VPMU per >>>> guest myself. >>>> >>>> However, VPMU has nothing to do with device model so I don't think it >>>> should be part of this series from that perspective. >>> vpmu is enabled globally on the xen command line, there's no way to >>> disable it on a per-guest basis, so AFAICS it will be enabled for >>> HMVlite guests which is wrong because we don't have a vlapic. >> Hmm, Boris specifically enabled vPMU to be available to all three >> kinds of guests, and PVH in it s current shape doesn't have a >> vLAPIC either. So making such a connection seems wrong to me. > IMHO, I would prefer the vPMU support in HVMlite guests to be tied to a > vlapic presence, so we can do it the HVM way instead of having to do > hypercalls. > > One think that could work is changing the is_hvm_* calls in vpmu.c to > has_vlapic. This way HVMlite guests could still use the PV vPMU > interface, but once a lapic is enabled we could use the native way. Yes, I think that would work. -boris