From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric B Munson Subject: Re: [PATCH 6/6 V2] Add age out of guest paused flag Date: Tue, 1 Nov 2011 16:10:07 -0400 Message-ID: <20111101201007.GD9852@mgebm.net> References: <1320091650-24682-1-git-send-email-emunson@mgebm.net> <1320091650-24682-7-git-send-email-emunson@mgebm.net> <4EB049C3.7080206@us.ibm.com> <20111101195111.GA9852@mgebm.net> <4EB04F5F.4010709@us.ibm.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zbGR4y+acU1DwHSi" Return-path: Received: from oz.csail.mit.edu ([128.30.30.239]:51895 "EHLO mail.mgebm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750829Ab1KAUKI (ORCPT ); Tue, 1 Nov 2011 16:10:08 -0400 Content-Disposition: inline In-Reply-To: <4EB04F5F.4010709@us.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Anthony Liguori Cc: avi@redhat.com, mingo@redhat.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, ryanh@linux.vnet.ibm.com --zbGR4y+acU1DwHSi Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, 01 Nov 2011, Anthony Liguori wrote: > On 11/01/2011 02:51 PM, Eric B Munson wrote: > >On Tue, 01 Nov 2011, Anthony Liguori wrote: > > > >>On 10/31/2011 03:07 PM, Eric B Munson wrote: > >>>The KVM_GUEST_PAUSED flag will prevent a guest from compaining about a= soft > >>>lockup but it can mask real soft lockups if the flag isn't cleared whe= n it is > >>>no longer relevant. This patch adds a kvm ioctl that the hypervisor w= ill use > >>>when it resumes a guest to start a timer for aging out the flag. The = time out > >>>will be specified by the hypervisor in the ioctl call. > >>> > >>>Signed-off-by: Eric B Munson > >> > >>Why not have the guest clear the flag when it acknowledges it? > >> > >>The hypervisor would unconditionally set the bit, and the guest > >>would do a testandclear to check if the bit is set. I think that > >>avoids the whole aging business. > >> > >>Regards, > >> > >>Anthony Liguori > > > >If you have a look at patch 5 of this series, the flag is cleared when t= he > >guest checks the validity of a soft lockup. However, the aging is meant= to > >cover the case where the guest never sees a soft lockup. We don't want = this > >flag to be stored for ever and end up delaying real soft lockup messages= =2E With > >that case in mind, I thought this was a good/simple compramise. >=20 > If the guest clears the flag, then I don't think you have to worry about = this. >=20 > Regards, >=20 > Anthony Liguori Except that the soft lockup doesn't trigger on every qemu "stop", only some= of them. The flag isn't cleared until the detector is triggered. Eric --zbGR4y+acU1DwHSi Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBAgAGBQJOsFIeAAoJEKhG9nGc1bpJ2Z4P/0bUvJwMZLKKRjhtnoC9pkZY UZRFbJj3RFFoFpLXo66Bc8c3XcPfqWYOtwy+BXhwBIpVsfHrIyrXvV3yxOlTmPF5 +ycqNwgnSEDGz2F/nduw+6PLNnVHuHfpCtzBR+UU7tk5e/QF830X6ZgnM7gcjrSm t7Ki9qK8NOwvE80Bnuv3kPQrH4spsZWssMUKW/pj86UbMXz3VuDIvhOjh490Aspm nAAkXAXlvlSZSuRXs2LSnwMZSZKWzuDCFpLvvqxa2AtcG0DPYYPM8Sko3In0GnJY yQAZ7P5A0ehi7nkmpRGkn8dmjDBvoKf3pQb5Vaf+ONolA00O0EtCmT6vXlt5aP/M 3CX2/PsUWtugXGHYu+IW1Tj7OsOlr1p+4rMsYGY5c+OrILR0+8a5mlO+3YM5/9DC 4/rFrTCD6oVq8HBhT4B5AS7tQOaAroc2cqdwpECl55N6YCcZusUrbkwdFTLOMva0 Ihk49ALroxog67tOY5fym4DkkjHPv5bh80Jj2bZlwd78kiCdpuvwtXS31o04Sx2q 6bwD9tuORZMRSd5gPCt3ZaRSqxHlGJ5ZR2SQW7eCozW0nY/+2C0dNngTu2Di7JVy bKFpREy7t4i0evcsy8f/dOkso/JFK4qc+pPbGMT9l5q8mLYeRHkyiiz33alN0EwQ TwuK1xGluzu1bfYgMPPP =UEvx -----END PGP SIGNATURE----- --zbGR4y+acU1DwHSi--