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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham 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 34CBCC433FE for ; Tue, 8 Dec 2020 14:35:37 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 6FB3823A69 for ; Tue, 8 Dec 2020 14:35:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6FB3823A69 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49122 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kme5W-0001ng-SK for qemu-devel@archiver.kernel.org; Tue, 08 Dec 2020 09:35:34 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57792) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kme3V-0000XG-7c; Tue, 08 Dec 2020 09:33:29 -0500 Received: from smtpout1.mo804.mail-out.ovh.net ([79.137.123.220]:39669) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kme3R-0000qD-UA; Tue, 08 Dec 2020 09:33:29 -0500 Received: from mxplan5.mail.ovh.net (unknown [10.108.1.76]) by mo804.mail-out.ovh.net (Postfix) with ESMTPS id 5893678D359F; Tue, 8 Dec 2020 15:33:13 +0100 (CET) Received: from kaod.org (37.59.142.97) by DAG8EX1.mxp5.local (172.16.2.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2044.4; Tue, 8 Dec 2020 15:33:11 +0100 Authentication-Results: garm.ovh; auth=pass (GARM-97G00269f5b6ba-dea0-4042-956e-51ad3a1da31a, 17D40A658B0D6C300559F39EE9B5E954A2DF46D1) smtp.auth=groug@kaod.org X-OVh-ClientIp: 82.253.208.248 Date: Tue, 8 Dec 2020 15:33:09 +0100 From: Greg Kurz To: Daniel Henrique Barboza Subject: Re: [PATCH 1/1] spapr.c: set a 'kvm-type' default value instead of relying on NULL Message-ID: <20201208153309.78825861@bahia.lan> In-Reply-To: <20201208134536.1012045-1-danielhb413@gmail.com> References: <20201208134536.1012045-1-danielhb413@gmail.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [37.59.142.97] X-ClientProxiedBy: DAG1EX2.mxp5.local (172.16.2.2) To DAG8EX1.mxp5.local (172.16.2.71) X-Ovh-Tracer-GUID: 717e6f63-7145-47da-acdb-a6d9f05d2b35 X-Ovh-Tracer-Id: 10279747626111048099 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedujedrudejiedgieeiucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuqfggjfdpvefjgfevmfevgfenuceurghilhhouhhtmecuhedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepfffhvffukfgjfhfogggtgfhisehtjeeftdertddvnecuhfhrohhmpefirhgvghcumfhurhiiuceoghhrohhugheskhgrohgurdhorhhgqeenucggtffrrghtthgvrhhnpeeuveeljefggfehtedujeegveeihfekvdfhjedtleehveetiefhfeetheffgefhffenucffohhmrghinhepghhnuhdrohhrghenucfkpheptddrtddrtddrtddpfeejrdehledrudegvddrleejnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmohguvgepshhmthhpqdhouhhtpdhhvghlohepmhigphhlrghnhedrmhgrihhlrdhovhhhrdhnvghtpdhinhgvtheptddrtddrtddrtddpmhgrihhlfhhrohhmpehgrhhouhhgsehkrghougdrohhrghdprhgtphhtthhopegurghvihgusehgihgsshhonhdrughrohhpsggvrghrrdhiugdrrghu Received-SPF: pass client-ip=79.137.123.220; envelope-from=groug@kaod.org; helo=smtpout1.mo804.mail-out.ovh.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Daniel, On Tue, 8 Dec 2020 10:45:36 -0300 Daniel Henrique Barboza wrote: > spapr_kvm_type() is considering 'vm_type=NULL' as a valid input, where > the function returns 0. This is relying on the current QEMU machine > options handling logic, where the absence of the 'kvm-type' option > will be reflected as 'vm_type=NULL' in this function. > > This is not robust, and will break if QEMU options code decides to propagate > something else in the case mentioned above (e.g. an empty string instead > of NULL). > > Let's avoid this entirely by setting a non-NULL default value in case of > no user input for 'kvm-type'. spapr_kvm_type() was changed to handle 3 fixed > values of kvm-type: "HV", "PR" and, if no kvm-type was set by the user, > DEFAULT_KVM_TYPE. This allows us always be predictable regardless of any > enhancements/changes made in QEMU options mechanics. > > While we're at it, let's also document in 'kvm-type' description what > happens if the user does not set this option. This information is based > on how the pseries kernel handles the KVM_CREATE_VM ioctl(), where the > default value '0' makes the kernel choose an available KVM module to > use, giving precedence to kvm_hv. This logic is described in the kernel > source file arch/powerpc/kvm/powerpc.c, function kvm_arch_init_vm(). > > Signed-off-by: Daniel Henrique Barboza > --- > > The case I mentioned in the second paragraph is happening when we try to > execute a pseries guest with '--enable-kvm' using Paolo's patch > "vl: make qemu_get_machine_opts static" [1]: > > $ sudo ./ppc64-softmmu/qemu-system-ppc64 -nographic -nodefaults -machine pseries --enable-kvm > qemu-system-ppc64: Unknown kvm-type specified '' > > This happens due to the differences between how qemu_opt_get() and > object_property_get_str() works when there is no 'kvm-type' specified. > See [2] for more info about the issue found. > > > [1] https://lists.gnu.org/archive/html/qemu-devel/2020-12/msg00471.html > [2] https://lists.gnu.org/archive/html/qemu-devel/2020-12/msg01578.html > > > hw/ppc/spapr.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index b7e0894019..32d938dc6a 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -3021,9 +3021,10 @@ static void spapr_machine_init(MachineState *machine) > qemu_cond_init(&spapr->fwnmi_machine_check_interlock_cond); > } > > +#define DEFAULT_KVM_TYPE "auto" > static int spapr_kvm_type(MachineState *machine, const char *vm_type) > { > - if (!vm_type) { > + if (!strcmp(vm_type, DEFAULT_KVM_TYPE)) { > return 0; > } > > @@ -3131,6 +3132,16 @@ static char *spapr_get_kvm_type(Object *obj, Error **errp) > { > SpaprMachineState *spapr = SPAPR_MACHINE(obj); > > + /* > + * In case the user didn't set 'kvm-type', return DEFAULT_KVM_TYPE > + * instead of NULL. This allows us to be more predictable with what > + * is expected to happen in spapr_kvm_type(), since we can stop relying > + * on receiving a 'NULL' parameter as a valid input there. > + */ Returning what is obviously a default value is straightforward enough that is doesn't need to a comment IMHO. > + if (!spapr->kvm_type) { > + return g_strdup(DEFAULT_KVM_TYPE); > + } > + > return g_strdup(spapr->kvm_type); Alternatively you could simply do: return g_strdup(spapr->kvm_type ? spapr->kvm_type : DEFAULT_KVM_TYPE); > } > > @@ -3273,7 +3284,11 @@ static void spapr_instance_init(Object *obj) > object_property_add_str(obj, "kvm-type", > spapr_get_kvm_type, spapr_set_kvm_type); > object_property_set_description(obj, "kvm-type", > - "Specifies the KVM virtualization mode (HV, PR)"); > + "Specifies the KVM virtualization mode (HV, PR)." Why not documenting "auto" as a valid option as well ? While here you could maybe convert HV and PR to lowercase in order to have a prettier "hv, pr, auto" set of valid values in the help string. You'd need to convert the related checks in spapr_kvm_type() to still check for the uppercase versions for compatibility, eg. by using g_ascii_strcasecmp(). > + " If not specified, defaults to any available KVM" > + " module loaded in the host. In case both kvm_hv" > + " and kvm_pr are loaded, kvm_hv takes precedence."); > + s/If not specified/If 'auto'/ and mention 'auto' as being the default value. > object_property_add_bool(obj, "modern-hotplug-events", > spapr_get_modern_hotplug_events, > spapr_set_modern_hotplug_events);