From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: Re: [Alacrityvm-devel] [KVM PATCH v2 1/2] KVM: export lockless GSI attribute Date: Mon, 26 Oct 2009 09:25:10 -0400 Message-ID: <4AE5A336.4010801@gmail.com> References: <20091023023512.3891.65889.stgit@dev.haskins.net> <20091023023845.3891.36857.stgit@dev.haskins.net> <4AE460F4.2090905@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigE57E2CB4BDDF16FE83E4824D" Cc: Gregory Haskins , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, alacrityvm-devel@lists.sourceforge.net To: Avi Kivity Return-path: Received: from qw-out-2122.google.com ([74.125.92.27]:37941 "EHLO qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754468AbZJZNZM (ORCPT ); Mon, 26 Oct 2009 09:25:12 -0400 In-Reply-To: <4AE460F4.2090905@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigE57E2CB4BDDF16FE83E4824D Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Avi Kivity wrote: > On 10/23/2009 04:38 AM, Gregory Haskins wrote: >> Certain GSI's support lockless injecton, but we have no way to detect >> which ones at the GSI level. Knowledge of this attribute will be >> useful later in the series so that we can optimize irqfd injection >> paths for cases where we know the code will not sleep. Therefore, >> we provide an API to query a specific GSI. >> >> =20 >=20 > Instead of a lockless attribute, how about a ->set_atomic() method. Fo= r=20 > msi this can be the same as ->set(), for non-msi it can be a function=20 > that schedules the work (which will eventually call ->set()). >=20 > The benefit is that we make a decision only once, when preparing the=20 > routing entry, and install that decision in the routing entry instead o= f=20 > making it again and again later. Yeah, I like this idea. I think we can also get rid of the custom workqueue if we do this as well, TBD. >=20 >> +int kvm_irq_check_lockless(struct kvm *kvm, u32 irq) >> =20 >=20 > bool kvm_irq_check_lockless(...) We lose the ability to detect failure (such as ENOENT) if we do this, but its moot if we move to the ->set_atomic() model, since this attribute is no longer necessary and this patch can be dropped. Kind Regards, -Greg --------------enigE57E2CB4BDDF16FE83E4824D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.11 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkrlozYACgkQP5K2CMvXmqHZwgCeLTEG8lKeRLjeurJiwL2vsltQ ajYAn0TBRYQfsKEt8V8+FXq7dK4/yhQT =+xg4 -----END PGP SIGNATURE----- --------------enigE57E2CB4BDDF16FE83E4824D--