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Mon, 08 Nov 2021 10:39:00 -0500 X-MC-Unique: OBEy6o-eNLKYS6BZTkV95g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 84468101F002 for ; Mon, 8 Nov 2021 15:38:59 +0000 (UTC) Received: from [10.39.192.185] (unknown [10.39.192.185]) by smtp.corp.redhat.com (Postfix) with ESMTP id AE8A960936; Mon, 8 Nov 2021 15:38:58 +0000 (UTC) Message-ID: <837be094-8a70-b364-3f85-5e6af8c05304@redhat.com> Date: Mon, 8 Nov 2021 16:38:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: Artificially target-dependend compiles To: Markus Armbruster , Paolo Bonzini References: <87czneyaw3.fsf@dusky.pond.sub.org> <2e4b52b0-b1fc-58c5-9631-fbf9d7f927fc@redhat.com> <87fss9u3zj.fsf@dusky.pond.sub.org> <87ilx3nk5p.fsf@dusky.pond.sub.org> From: Thomas Huth In-Reply-To: <87ilx3nk5p.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -65 X-Spam_score: -6.6 X-Spam_bar: ------ X-Spam_report: (-6.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-3.06, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.29 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 08/11/2021 09.09, Markus Armbruster wrote: > Markus Armbruster writes: > > [...] > >> I just ran into an instance that may be clearer. >> >> The "rocker" device is target-independent (hw/net/meson.build adds it to >> softmmu_ss), but linked only for selected targets (hw/net/Kconfig has >> depends on PCI && MSI_NONBROKEN). >> >> This makes our build machinery put CONFIG_ROCKER in >> $TARGET-softmmu-config-devices.h, and poison it in config-poison.h. >> Feels uncalled for. > > Hmm, maybe not. > > Our build process links the rocker stuff for selected targets. > > The QAPI schema provides rocker definitions unconditionally. > QAPI-generated rocker code gets linked for all targets. The > command handlers resolve to the real ones when on the selected targets, > else to stubs. > > This works and is fairly simple. We link a bit of useless code > (QAPI-generated and stubs). query-qmp-schema can't tell us whether > rocker is present, which is sad, but there's a work-around: > qom-list-types. > > We may still run into cases where we really want query-qmp-schema to > tell, say because there is no easy work-around. > > Making the QAPI schema definitions properly conditional does the trick, > but makes code artificially target-dependent, slowing down the build. > It can also lead to extra #ifdeffery, because now useless code doesn't > compile anymore. > > Simply not poisoning the CONFIG_FOO when the FOO code is actually > target-independent avoids the target-dependency, but also messes up > introspection: new the FOO stuff is present for all targets when *any* > of them has it. This cure feels worse than the disease. > > Needs more thought. Hmm, we used to have a config-all-devices.mak file in the past (see commit a98006bc798169e which removed it), maybe we could re-introduce something similar again, but producing a config-all.h header file instead? So that this header file contains switches like CONFIG_ANY_ACPI_VMGENID and CONFIG_ANY_ROCKER that are set if any of the targets uses the device ... and these switches would not get poisoned in common code... ? Thomas