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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id n17sm13723945wrw.69.2020.11.09.08.21.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Nov 2020 08:21:35 -0800 (PST) To: Markus Armbruster References: <20201109133931.979563-1-pbonzini@redhat.com> <20201109133931.979563-4-pbonzini@redhat.com> <87eel25xud.fsf@dusky.pond.sub.org> From: Paolo Bonzini Subject: Re: [PATCH v2 3/6] qemu-option: restrict qemu_opts_set to merge-lists QemuOpts Message-ID: <0defd899-184d-549e-a799-7000f7b9c92d@redhat.com> Date: Mon, 9 Nov 2020 17:21:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <87eel25xud.fsf@dusky.pond.sub.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/09 00:04:29 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09/11/20 16:55, Markus Armbruster wrote: >> QemuOptsList *net = qemu_find_opts("net"); >> - qemu_opts_set(net, NULL, "type", "nic", &error_abort); >> + qemu_opts_parse(net, "nic", true, &error_abort); >> #ifdef CONFIG_SLIRP >> - qemu_opts_set(net, NULL, "type", "user", &error_abort); >> + qemu_opts_parse(net, "user", true, &error_abort); >> #endif >> } >> > Looks safe to me, but I don't quite get why you switch to > qemu_opts_parse(). The commit message explains it is "so that > qemu_opts_set is now only used on merge-lists QemuOptsList (for which it > makes the most sense indeed)..." Is there anything wrong with using ot > on non-merge-lists QemuOptsList? I would *expect* a function named qemu_opts_set to do two things: 1. setting an option in a merge-lists QemuOptsList, such as -kernel. This is indeed what we mostly use qemu_opts_set for. 2. setting an option in a non-merge-lists QemuOptsList with non-NULL id, similar to -set. QEMU does not use qemu_opts_set for the latter (see qemu_set_option) because it wants to use qemu_opts_find rather than qemu_opts_create. In fact it wouldn't *work* to use qemu_opts_set for the latter because qemu_opts_set uses fail_if_exists==1. So: -> For non-merge-lists QemuOptsList and non-NULL id, it is debatable that qemu_opts_set fails if the (QemuOptsList, id) pair already exists On the other hand, I would not *expect* qemu_opts_set to create a non-merge-lists QemuOpts with a single option; which it does, though. This leads us directly to: -> For non-merge-lists QemuOptsList and NULL id, qemu_opts_set hardly adds value over qemu_opts_parse. It does skip some parsing and unescaping, but its two call sites don't really care. So qemu_opts_set has warty behavior for non-merge-lists QemuOptsList if id is non-NULL, and it's mostly pointless if id is NULL. My solution to keeping the API as simple as possible is to limit qemu_opts_set to merge-lists QemuOptsList. For them, it's useful (we don't want comma-unescaping for -kernel) *and* has sane semantics. >> + g_assert(!QTAILQ_EMPTY(&list->head)); >> + >> + /* set it again */ >> + qemu_opts_set(list, "str3", "value", &error_abort); >> g_assert(!QTAILQ_EMPTY(&list->head)); > > This one not. > > What are you trying to accomplish? Improve the testcase, though I should have mentioned it in the commit message. Basically emulating "-kernel bc -kernel def". Paolo