From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: Host latency peaks due to kvm-intel Date: Sun, 26 Jul 2009 16:23:28 +0200 Message-ID: <4A6C66E0.6050306@web.de> References: <4A68A6E5.6010808@siemens.com> <4A68BD5D.1070302@gmail.com> <4A6981B0.3000008@siemens.com> <4A6ABF28.1010602@redhat.com> <4A6AD69E.7030201@web.de> <4A6B0837.6010608@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig6E1868085BDDC26FC6305140" Cc: Gregory Haskins , kvm-devel , RT , "Yang, Sheng" To: Avi Kivity Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:38424 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753512AbZGZOXi (ORCPT ); Sun, 26 Jul 2009 10:23:38 -0400 In-Reply-To: <4A6B0837.6010608@redhat.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig6E1868085BDDC26FC6305140 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Avi Kivity wrote: > On 07/25/2009 12:55 PM, Jan Kiszka wrote: >> Avi Kivity wrote: >> =20 >>> On 07/24/2009 12:41 PM, Jan Kiszka wrote: >>> =20 >>>> I vaguely recall that someone promised to add a feature reporting >>>> facility for all those nice things, modern VM-extensions may or may = not >>>> support (something like or even an extension of /proc/cpuinfo). What= is >>>> the state of this plan? Would be specifically interesting for Intel >>>> CPUs >>>> as there seem to be many of them out there with restrictions for >>>> special >>>> use cases - like real-time. >>>> >>>> =20 >>> Newer kernels do report some vmx features (like flexpriority) in >>> /proc/cpuinfo but not all. >>> >>> =20 >> >> Ah, nice. Then we just need this? >> >> ------------> >> >> From: Jan Kiszka >> Subject: [PATCH] x86: Report VMX feature vwbinvd >> >> Not all VMX-capable CPUs support guest exists on wbinvd execution. If >> this is not supported, the instruction will run natively on behalf of >> the guest. This can cause multi-millisecond latencies to the host whic= h >> is very problematic in real-time scenarios. >> >> Report the wbinvd trapping feature along with other VMX feature flags,= >> calling it 'vwbinvd' ('virtual wbinvd'). >> >> =20 >=20 > What about AMD cpus that can always trap wbinvd? do we set the bit or > do we trust the user to know that it isn't needed on AMD (I suppose the= > latter)? I also think that the feature flags should remain vendor-specific. >=20 > This should go in via tip.git, it isn't really kvm related (except that= > kvm should start reading these caps one day instead of querying the > hardware directly). >=20 OK, will go that way. Probably I will also add some flags for AMD's NPT, Intel's EPT and they new unrestricted guest mode at this chance. Jan --------------enig6E1868085BDDC26FC6305140 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkpsZukACgkQniDOoMHTA+nWuwCdF5fOXnPWXRbUMg8uJ6Pp1+Z+ x38Aniy7i5LCw+qpLkeOOiVnhyZNn5dY =EvJn -----END PGP SIGNATURE----- --------------enig6E1868085BDDC26FC6305140--