From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: KVM handling external interrupts Date: Sun, 10 Jun 2012 12:16:01 +0200 Message-ID: <4FD473E1.6070302@web.de> References: <4FD062BC.5090703@web.de> <4FD06E27.9020201@web.de> <4FD087A7.8000508@web.de> <4FD08C28.9070600@web.de> <4FD09A6C.4000601@web.de> <4FD0C353.7030707@web.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig18C393024645ED61B5856CC0" Cc: Alex Landau , Dan Tsafrir , sheng qiu , kvm , Muli Ben-Yehuda , Nadav Har'El , Nadav Amit To: Abel Gordon Return-path: Received: from mout.web.de ([212.227.17.11]:51320 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451Ab2FJKQK (ORCPT ); Sun, 10 Jun 2012 06:16:10 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig18C393024645ED61B5856CC0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2012-06-10 10:41, Abel Gordon wrote: > Jan Kiszka wrote on 07/06/2012 18:05:55: >=20 >> It remains a fragile approach: >> - host-side reverse translations may not return a stable result, thus= >> may require to redo this step several times >> - the guest may decide to remove/disable the device you chose for >> appending the IDT >> - changing the real BAR size can confuse the guest, or it only maps >> what it requires of the real device >> That's why I consider it nasty. >=20 > Yep, these are corner cases we should deal with but they are not part > of the common case/critical path. >=20 >> I'm wondering if redirecting (to different cores) or masking (at >> device/IOAPIC/LAPIC level) of non-guest interrupts and only relying on= >> preemption timer/NMI isn't simpler. Then you wouldn't have to shadow t= he >> IDT. >=20 > Yep, as we suggested in the paper, that could be also an alternative. > Is it really simpler ? Again, depends who you ask and what you need to > change. > All the alternatives have a set of pros and cons. >=20 For sure. But avoiding the shadow IDT would likely mean avoiding userspace changes for KVM. And that means simplification. And avoid PCI dependencies. Jan --------------enig18C393024645ED61B5856CC0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk/Uc+EACgkQitSsb3rl5xQ4iACggeVWcxbXjIZjcIB/Yb06eqV3 D/EAnjr29lnkyV8hl1DvCZRDWKzi9brx =CpyM -----END PGP SIGNATURE----- --------------enig18C393024645ED61B5856CC0--