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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 93802C3ABC3 for ; Mon, 12 May 2025 18:38:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uEY2m-0003OA-SN; Mon, 12 May 2025 14:38:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uEY2e-0003I8-Tn for qemu-devel@nongnu.org; Mon, 12 May 2025 14:38:21 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uEY2c-0004EH-Gx for qemu-devel@nongnu.org; Mon, 12 May 2025 14:38:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747075097; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sMAnQk66oVPj8Mjos3U3u2tAvgXVUMwSTvkBFFFM0lQ=; b=KZ14qMV9DpFf6dBDGwcbtic3LVNamPm7zanG81TwyxF8YcGnF2HRXUpzp4JS1sfpa2M+ge y9upo2+QSajqY2UEmWkL4N21imAE7SnT0mfqe3LoCCqHoP0nB50Xruc4rOk3EcgJJDkG2t yieVxmd/dgEva4Jn679dORtOeVv1MFM= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-287-1EYA3Mb4MNS5G0SlRhi-tA-1; Mon, 12 May 2025 14:38:14 -0400 X-MC-Unique: 1EYA3Mb4MNS5G0SlRhi-tA-1 X-Mimecast-MFC-AGG-ID: 1EYA3Mb4MNS5G0SlRhi-tA_1747075093 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 10BC01800DA1; Mon, 12 May 2025 18:38:13 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.162]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C15A130001A1; Mon, 12 May 2025 18:38:10 +0000 (UTC) Date: Mon, 12 May 2025 19:38:07 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Pierrick Bouvier , qemu-devel@nongnu.org, Peter Maydell , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini , Richard Henderson Subject: Re: [PATCH RFC 00/10] qapi: remove all TARGET_* conditionals from the schema Message-ID: References: <20250508135816.673087-1-berrange@redhat.com> <874ixt6gsd.fsf@pond.sub.org> <874ixt2e2l.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <874ixt2e2l.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.551, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sat, May 10, 2025 at 08:08:02AM +0200, Markus Armbruster wrote: > Daniel P. Berrangé writes: > > > On Fri, May 09, 2025 at 03:43:30PM +0200, Markus Armbruster wrote: > >> Daniel P. Berrangé writes: > >> > Even if we had a QAPI schema that didn't vary per target, this is > >> > repeated probing is tricky to avoid when we have completely independant > >> > binaries. We would need QEMU to have some internal "build id", so that > >> > we could detect that all binaries came from the same build, to let us > >> > avoid re-probing each binary. > >> > >> Back when I created QAPI/QMP introspection, I floated the idea to put > >> something into the QMP greeting to enable safe caching. Libvirt > >> developers told me they didn't need that. I don't remember the details, > >> but I guess the cache invalidation they already had was deemed good > >> enough. > > > > I don't recall that discussion, but I would think the problem is > > that we probe much more than just QMP schema. Actually thinking > > about it, the fact that we probe more than just QMP schema means > > my idea of probing once and getting the answer for all targets > > may not be practical. Some of the query-xxx commands we run will > > likely need to know the target. > > Yes. > > We could split the cache along validity conditions. Possibly worth the > extra complexity if expensive probes then live longer in their cache. > > I'd love to have a list of probes libvirt runs and why. We don't record the 'why' I'm afraid, so answer the 'why' is pretty much a case of having to read the code :-( The list of probes is also somewhat metadata driven, starting from: https://gitlab.com/libvirt/libvirt/-/blob/6ff8d08777ebbcb9a1e11534c3a3341fbf0343e8/src/qemu/qemu_capabilities.c?page=6#L5718 you would have to then work backwards for each virQMEUCapsProbeQMP method we call. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|