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 26F5EC3DA7F for ; Wed, 31 Jul 2024 06:31:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sZ2rb-00069t-Tj; Wed, 31 Jul 2024 02:31:07 -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 1sZ2rV-00068u-CE for qemu-devel@nongnu.org; Wed, 31 Jul 2024 02:31:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sZ2rQ-0005bQ-AC for qemu-devel@nongnu.org; Wed, 31 Jul 2024 02:30:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722407454; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hFqmm5B5rAwk5dtYSiYPSjKNDVSS+d62iKdjRKaAh00=; b=C1jiCzXd3HBPrBhtaCoxGu8n9kVPQOjxb8AMXDO+GoWy3l56G6L5ahkdLy6Q8fK+ru+qcC p5A57z0rT9eX99CEDqSqXU7glnD4+RaVeZ4DlFfvvFnIuhOnivy+5HbU3mUSg6tJMb3m6u 8EKTPWdq4d4uZBt8HSMCi5gRIKJcAV8= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-132-dV63mwN3N2CIzUbGrHsDMw-1; Wed, 31 Jul 2024 02:30:51 -0400 X-MC-Unique: dV63mwN3N2CIzUbGrHsDMw-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 218551955D45; Wed, 31 Jul 2024 06:30:49 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.65]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AA30A19560AE; Wed, 31 Jul 2024 06:30:48 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8DAFF21E6690; Wed, 31 Jul 2024 08:30:46 +0200 (CEST) From: Markus Armbruster To: Daniel Henrique Barboza Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, richard.henderson@linaro.org, berrange@redhat.com, eduardo@habkost.net, Andrew Jones Subject: Re: [PATCH v2 2/2] qom/object, accel-system: add support to Accel globals In-Reply-To: <20240703204149.1957136-3-dbarboza@ventanamicro.com> (Daniel Henrique Barboza's message of "Wed, 3 Jul 2024 17:41:49 -0300") References: <20240703204149.1957136-1-dbarboza@ventanamicro.com> <20240703204149.1957136-3-dbarboza@ventanamicro.com> Date: Wed, 31 Jul 2024 08:30:46 +0200 Message-ID: <87bk2ekr8p.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.125, 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_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org I apologize for the delay. Daniel Henrique Barboza writes: > We're not honouring KVM options that are provided by any -accel option > aside from the first. In this example: > > qemu-system-riscv64 -accel kvm,riscv-aia=emul (...) \ > -accel kvm,riscv-aia=hwaccel > > 'riscv-aia' will be set to 'emul', ignoring the last occurrence of the > option that set 'riscv-aia' to 'hwaccel'. The way you phrase this, it sounds like a bug. But as far as I know, -accel is meant to have fallback semantics: we use the first one that works. Perhaps: -accel has fallback semantics, i.e. we try accelerators in order until we find one that works. Any remainder is ignored. Because of that, you can't override properties like this: qemu-system-riscv64 -accel kvm,riscv-aia=emul (...) \ -accel kvm,riscv-aia=hwaccel When KVM is available, 'riscv-aia' will be set to 'emul', and the second -accel is ignored. When KVM is not available, neither option works, and the command fails. Why would you want to override accelerator properties? Aside: not diagnosing obvious errors in fallback options we don't use is not nice. Not this patch's problem. > A failed attempt to solve this issue by setting 'merge_lists' can be > found in [1]. I guess this failed because it destroyed the fallback semantics. Correct? > A different approach was suggested in [2]: enable global > properties for accelerators. This allows an user to override any accel > setting by using '-global' and we won't need to change how '-accel' opts > are handled. > > This is done by calling object_prop_set_globals() in > accel_init_machine(). As done in device_post_init(), user's global > props take precedence over compat props so object_prop_set_globals() is > called after object_set_accelerator_compat_props(). > > object_prop_check_globals() is then changed to recognize TYPE_ACCEL > globals as valid. Would it make sense to enable -global for user-creatable objects (-object), too? > Re-using the fore-mentioned example we'll be able to set > riscv-aia=hwaccel by doing the following: > > qemu-system-riscv64 -accel kvm,riscv-aia=emul (...) \ > -global kvm-accel.riscv-aia=hwaccel I'm confused. -accel kvm,riscv-aia=emul creates accelerator kvm (which is an instance of class "kvm-accel") and sets its property "riscv-aia" to "emul". -global kvm-accel,riscv-aia=hwaccel changes the (global) default value of class "kvm-accel" property "riscv-aia". Are you *sure* your example sets "riscv-aia" to "hwaccel"? > [1] https://lore.kernel.org/qemu-devel/20240701133038.1489043-1-dbarboza@ventanamicro.com/ > [2] https://lore.kernel.org/qemu-devel/CABgObfbVJkCdpHV2uA7LGTbYEaoaizrbeG0vNo_T1ua5b=jq7Q@mail.gmail.com/ > > Reported-by: Andrew Jones > Suggested-by: Paolo Bonzini > Signed-off-by: Daniel Henrique Barboza