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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id h13-20020a1709063c0d00b008b176df2899sm1112472ejg.160.2023.03.31.09.29.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Mar 2023 09:29:28 -0700 (PDT) Date: Fri, 31 Mar 2023 18:29:27 +0200 From: Igor Mammedov To: Eric DeVolder Cc: "Michael S. Tsirkin" , shannon.zhaosl@gmail.com, ani@anisinha.ca, peter.maydell@linaro.org, qemu-arm@nongnu.org, qemu-devel@nongnu.org, marcel.apfelbaum@gmail.com, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, boris.ostrovsky@oracle.com Subject: Re: [PATCH 2/2] hw/acpi: i386: bump MADT to revision 5 Message-ID: <20230331182927.04e0518b@imammedo.users.ipa.redhat.com> In-Reply-To: References: <20230328155926.2277-1-eric.devolder@oracle.com> <20230328155926.2277-3-eric.devolder@oracle.com> <20230329010126-mutt-send-email-mst@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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_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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, 29 Mar 2023 08:16:26 -0500 Eric DeVolder wrote: > On 3/29/23 00:03, Michael S. Tsirkin wrote: > > On Tue, Mar 28, 2023 at 11:59:26AM -0400, Eric DeVolder wrote: > >> Currently i386 QEMU generates MADT revision 3, and reports > >> MADT revision 1. ACPI 6.3 introduces MADT revision 5. > >> > >> For MADT revision 4, that introduces ARM GIC structures, which do > >> not apply to i386. > >> > >> For MADT revision 5, the Local APIC flags introduces the Online > >> Capable bitfield. > >> > >> Making MADT generate and report revision 5 will solve problems with > >> CPU hotplug (the Online Capable flag indicates hotpluggable CPUs). > >> > >> Signed-off-by: Eric DeVolder > > > > I am looking for ways to reduce risk of breakage with this. > > We don't currently have a reason to change it if cpu > > hotplug is off, do we? Maybe make it conditional on that. > > By "cpu hotplug off", do you mean, for example, no maxcpus= option? > In other words, how should I detect "cpu hotplug off"? > eric I'm not sure that it's possible disable CPU hotplug at all. even if one doesn't have maxcpus on CLI present CPUs are described as hotpluggbale and can be unplugged and re-plugged later.