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[79.176.118.93]) by smtp.gmail.com with ESMTPSA id d3sm6422378wre.91.2020.11.07.06.28.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Nov 2020 06:28:56 -0800 (PST) Date: Sat, 7 Nov 2020 09:28:47 -0500 From: "Michael S. Tsirkin" To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [PULL v4 44/48] piix4: don't reserve hw resources when hotplug is off globally Message-ID: <20201107092610-mutt-send-email-mst@kernel.org> References: <20200929071948.281157-1-mst@redhat.com> <20200929071948.281157-45-mst@redhat.com> <5b79133f-374e-8a8f-6aeb-bd5313dc8eb1@redhat.com> <56a067f8-945f-cab4-d80e-6706ae446705@redhat.com> MIME-Version: 1.0 In-Reply-To: <56a067f8-945f-cab4-d80e-6706ae446705@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/07 03:59:37 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, 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: Peter Maydell , Eduardo Habkost , QEMU Developers , Aleksandar Markovic , Igor Mammedov , Ani Sinha , Paolo Bonzini , Aurelien Jarno , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, Nov 07, 2020 at 03:18:24PM +0100, Philippe Mathieu-Daudé wrote: > On 11/7/20 1:22 PM, Ani Sinha wrote: > > On Sat, Nov 7, 2020 at 3:40 PM Philippe Mathieu-Daudé wrote: > >> > >> Hi, > >> > >> On 9/29/20 9:22 AM, Michael S. Tsirkin wrote: > >>> From: Ani Sinha > >>> > >>> When acpi hotplug is turned off for both root pci bus as well as for pci > >>> bridges, we should not generate the related ACPI code for DSDT table or > >>> initialize related hw ports or reserve hw resources. This change makes > >>> sure all those operations are turned off in the case ACPI pci hotplug is > >>> off globally. > >>> > >>> In this change, we also make sure ACPI code for the PCNT method are only > >>> added when bsel is enabled for the corresponding pci bus or bridge hotplug > >>> is turned on. > >> > >> I'm trying to understand the following build failure using gcc 9.3.0 > >> on Ubuntu: > >> > >> [2567/3684] Compiling C object > >> libqemu-x86_64-softmmu.fa.p/hw_i386_acpi-build.c.o > >> FAILED: libqemu-x86_64-softmmu.fa.p/hw_i386_acpi-build.c.o > >> ../hw/i386/acpi-build.c: In function 'build_append_pci_bus_devices': > >> ../hw/i386/acpi-build.c:496:9: error: 'method' may be used uninitialized > >> in this function [-Werror=maybe-uninitialized] > >> 496 | aml_append(parent_scope, method); > >> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >> cc1: all warnings being treated as errors > >> > ... > >>> static void acpi_get_misc_info(AcpiMiscInfo *info) > >>> @@ -456,10 +460,12 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus, > >>> } > >>> > >>> /* Append PCNT method to notify about events on local and child buses. > >>> - * Add unconditionally for root since DSDT expects it. > >>> + * Add this method for root bus only when hotplug is enabled since DSDT > >>> + * expects it. > >>> */ > >>> - method = aml_method("PCNT", 0, AML_NOTSERIALIZED); > >>> - > >>> + if (bsel || pcihp_bridge_en) { > >>> + method = aml_method("PCNT", 0, AML_NOTSERIALIZED); > >>> + } > >> > >> build_append_pci_bus_devices() is not easy to follow and could certainly > >> benefit from a refactor. > > > > Hmm, ok will do that in my spare time. > > > >> > >> So here, before 'method' was always reinitialized. Now not always, > >> so it can be any value set in the big for() loop before... > > > > In line 467 above, method is initialized when bsel is available or > > pcihp is enabled. In line 496, it is appended to the parent scope only > > under those conditions as well. Basically, in hunks > > > > + if (bsel || pcihp_bridge_en) { > > + method = aml_method("PCNT", 0, AML_NOTSERIALIZED); > > + } > > > > and > > + > > + if (bsel || pcihp_bridge_en) { > > + aml_append(parent_scope, method); > > + } > > > > the conditions are exactly the same. > > The problem is in the (!bsel && !pcihp_bridge_en) case, > what 'method' is used there? Um ... where exactly?