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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id q10sm10643530ejn.3.2022.02.14.04.36.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Feb 2022 04:36:36 -0800 (PST) Date: Mon, 14 Feb 2022 13:36:34 +0100 From: Igor Mammedov To: Ani Sinha , QEMU Developers , David Hildenbrand Subject: Re: 9 TiB vm memory creation Message-ID: <20220214133634.248d7de0@redhat.com> In-Reply-To: References: 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: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.083, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 14 Feb 2022 10:54:22 +0530 (IST) Ani Sinha wrote: > Hi Igor: > > I failed to spawn a 9 Tib VM. The max I could do was a 2 TiB vm on my > system with the following commandline before either the system > destabilized or the OOM killed killed qemu > > -m 2T,maxmem=9T,slots=1 \ > -object memory-backend-file,id=mem0,size=2T,mem-path=/data/temp/memfile,prealloc=off \ > -machine memory-backend=mem0 \ > -chardev file,path=/tmp/debugcon2.txt,id=debugcon \ > -device isa-debugcon,iobase=0x402,chardev=debugcon \ > > I have attached the debugcon output from 2 TiB vm. > Is there any other commandline parameters or options I should try? > > thanks > ani $ truncate -s 9T 9tb_sparse_disk.img $ qemu-system-x86_64 -m 9T \ -object memory-backend-file,id=mem0,size=9T,mem-path=9tb_sparse_disk.img,prealloc=off,share=on \ -machine memory-backend=mem0 works for me till GRUB menu, with sufficient guest kernel persuasion (i.e. CLI limit ram size to something reasonable) you can boot linux guest on it and inspect SMBIOS tables comfortably. With KVM enabled it bails out with: qemu-system-x86_64: kvm_set_user_memory_region: KVM_SET_USER_MEMORY_REGION failed, slot=1, start=0x100000000, size=0x8ff40000000: Invalid argument all of that on a host with 32G of RAM/no swap.