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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id z21-20020a1709063a1500b006da6436819dsm6648341eje.173.2022.03.14.03.35.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Mar 2022 03:35:33 -0700 (PDT) Date: Mon, 14 Mar 2022 11:35:32 +0100 From: Igor Mammedov To: David Woodhouse Subject: Re: [PATCH] x86: q35: require split irqchip for large CPU count Message-ID: <20220314113532.10518837@redhat.com> In-Reply-To: <8d4912d595bcaca36013e22060c22c1bfe3c44c1.camel@infradead.org> References: <20220311143901.96481-1-imammedo@redhat.com> <8d4912d595bcaca36013e22060c22c1bfe3c44c1.camel@infradead.org> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=imammedo@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: pbonzini@redhat.com, qemu-devel@nongnu.org, mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 11 Mar 2022 14:58:41 +0000 David Woodhouse wrote: > On Fri, 2022-03-11 at 09:39 -0500, Igor Mammedov wrote: > > if VM is started with: > > > > -enable-kvm -smp 256 > > > > without specifying 'split' irqchip, VM might eventually boot > > but no more than 255 CPUs will be operational and following > > error messages in guest could be observed: > > ... > > smpboot: native_cpu_up: bad cpu 256 > > ... > > It's a regression introduced by [1], which removed dependency > > on intremap=on that were implicitly requiring 'split' irqchip > > and forgot to check for 'split' irqchip. > > Instead of letting VM boot a broken VM, error out and tell > > user how to fix CLI. > > Hm, wasn't that already fixed in the patches I posted in December? It might be, could you point to the commit/series that fixed it. Regardless of that, fixing it in recent kernels doesn't help as still supported kernels are still affected by it. If there is a way to detect that fix, I can add to q35 a compat property and an extra logic to enable kernel-irqchip if fix is present. Otherwise the fix does not exist until minimum supported kernel version reaches version where it was fixed.