From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 627D7C433DB for ; Tue, 5 Jan 2021 13:25:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3623B225AC for ; Tue, 5 Jan 2021 13:25:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728972AbhAENZC (ORCPT ); Tue, 5 Jan 2021 08:25:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726018AbhAENZB (ORCPT ); Tue, 5 Jan 2021 08:25:01 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10B67C061574; Tue, 5 Jan 2021 05:24:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Mime-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=wCbTCKu2V4xRVVvUgXORcRvGv5C7sorxJ/PBkiWHohI=; b=j4o46+G4MpGIUXsR/bCNbA6HE2 1ZM01ODyu2+a5NL4gpBy8yJ2flZ8O5VN2vxGkKU7IGc2FvTbB0pz4qH5sFTdLd8+z1wkG856c/w9k Kj1SHa+gfaYmLXDobtECBGygVKZAmUK6tI1HNJVxw17Q0WzuibvhmJAOfjpDUjNjyZMUupqE9yeCA VhM6DQTSQxpHheHj17Acqoq0ToM8d5Zvj4noHQCsgu2E2jsQ5C6jJRZBZFn01uUpwedEDGRqCwpoS 0u2L8cbtATiJVoaTuON+Fz4N9yQ1pIzJfCHyj0YOUYdBiiFlyawPdFKtuM3LKO8MMnU0H405YLR3s DdUGFRXA==; Received: from [54.239.6.185] (helo=edge-cache-257.e-hkg50.amazon.com) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kwmJb-0004jA-5y; Tue, 05 Jan 2021 13:23:59 +0000 Message-ID: Subject: Re: [PATCH RFC 10/39] KVM: x86/xen: support upcall vector From: David Woodhouse To: Joao Martins , Ankur Arora Cc: Boris Ostrovsky , Paolo Bonzini , Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 05 Jan 2021 13:23:56 +0000 In-Reply-To: References: <20190220201609.28290-1-joao.m.martins@oracle.com> <20190220201609.28290-11-joao.m.martins@oracle.com> <71753a370cd6f9dd147427634284073b78679fa6.camel@infradead.org> <53baeaa7-0fed-d22c-7767-09ae885d13a0@oracle.com> <4ad0d157c5c7317a660cd8d65b535d3232f9249d.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-ScCGivhKzh9yLtcayfha" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by merlin.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-ScCGivhKzh9yLtcayfha Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2021-01-05 at 12:11 +0000, Joao Martins wrote: > On 1/1/21 2:33 PM, David Woodhouse wrote: > > What it does actually mean in the short term is that as I update your > > KVM_IRQ_ROUTING_XEN_EVTCHN support, I probably *won't* bother to add a > > 'priority' field to struct kvm_irq_routing_xen_evtchn to make it > > extensible to FIFO event channels. We can always add that later. > >=20 > > Does that seem reasonable? > >=20 >=20 > Yes, makes sense IMHO. Guests need to anyway fallback to 2L if the > evtchnop_init_control hypercall fails, and the way we are handling events= , > doesn't warrant FIFO event channel support as mandatory. Right. I think it's perfectly OK to declare that we aren't going to support FIFO event channel acceleration in Linux/KVM, and anyone who really wants to support them would have to do it entirely in userspace. The only reason a VMM would really need to support FIFO event channels is if we're insane enough to want to do live migration from actual Xen, of guests which were previously using them. While I make no comment about my mental state, I can happily observe that I don't have guests which currently use FIFO support. --=-ScCGivhKzh9yLtcayfha Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTkwMTAyMDAwMDAwWhcNMjIwMTAxMjM1 OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRlYWQub3JnMIIBIjANBgkqhkiG9w0B AQEFAAOCAQ8AMIIBCgKCAQEAsv3wObLTCbUA7GJqKj9vHGf+Fa+tpkO+ZRVve9EpNsMsfXhvFpb8 RgL8vD+L133wK6csYoDU7zKiAo92FMUWaY1Hy6HqvVr9oevfTV3xhB5rQO1RHJoAfkvhy+wpjo7Q cXuzkOpibq2YurVStHAiGqAOMGMXhcVGqPuGhcVcVzVUjsvEzAV9Po9K2rpZ52FE4rDkpDK1pBK+ 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