From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36574) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d03rO-0003zi-Gi for qemu-devel@nongnu.org; Mon, 17 Apr 2017 06:26:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d03rL-0005pY-Dc for qemu-devel@nongnu.org; Mon, 17 Apr 2017 06:26:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36216) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d03rL-0005nS-8F for qemu-devel@nongnu.org; Mon, 17 Apr 2017 06:26:15 -0400 Date: Mon, 17 Apr 2017 18:26:07 +0800 From: Peter Xu Message-ID: <20170417102607.GE16703@pxdev.xzpeter.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] qemu memory manage question List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "jack.chen" Cc: qemu On Mon, Apr 17, 2017 at 06:09:11PM +0800, jack.chen wrote: > hello,I have some questions about memory allocation in qemu for > virtual machine.I found when configure_accelerator function was called > ,memory slots were registered to KVM,but at that time address_space > have not been initialized and ram have not been allocated,it is really > confused me,Thanks a lot!! Here's how I understand it... configure_accelerator() does not register memory slots in KVM. Instead, it registers memory listeners. See kvm_memory_listener_register(), especially: kml->listener.region_add = kvm_region_add; That's the hook function to be called when there are new memory region added to the system. Further, when RAM is initialzed, it'll modify the address space layout of system_memory, and the registered listener of KVM (kvm_region_add) will be invoked, it'll further sync with kvm. It should be in the following path if you break at kvm_region_add in gdb: #0 0x00005555557ba13a in kvm_region_add (listener=0x5555568330c0, section=0x7fffffffd310) at /root/git/qemu/kvm-all.c:859 #1 0x00005555557c1910 in address_space_update_topology_pass (as=0x55555629e240 , old_view=0x5555567a7090, new_view=0x5555568d3460, adding=true) at /root/git/qemu/memory.c:871 #2 0x00005555557c19f3 in address_space_update_topology (as=0x55555629e240 ) at /root/git/qemu/memory.c:886 #3 0x00005555557c1b41 in memory_region_transaction_commit () at /root/git/qemu/memory.c:922 #4 0x00005555557c4bfd in memory_region_update_container_subregions (subregion=0x5555568d2fc0) at /root/git/qemu/memory.c:2075 #5 0x00005555557c4c64 in memory_region_add_subregion_common (mr=0x5555567a5830, offset=0, subregion=0x5555568d2fc0) at /root/git/qemu/memory.c:2085 #6 0x00005555557c4ca0 in memory_region_add_subregion (mr=0x5555567a5830, offset=0, subregion=0x5555568d2fc0) at /root/git/qemu/memory.c:2093 #7 0x000055555583fd68 in pc_memory_init (pcms=0x5555567a4100, system_memory=0x5555567a5830, rom_memory=0x5555568d21a0, ram_memory=0x7fffffffd550) at /root/git/qemu/hw/i386/pc.c:1383 #8 0x0000555555847363 in pc_q35_init (machine=0x5555567a4100) at /root/git/qemu/hw/i386/pc_q35.c:147 #9 0x0000555555847cac in pc_init_v2_9 (machine=0x5555567a4100) at /root/git/qemu/hw/i386/pc_q35.c:310 #10 0x00005555558f7cf8 in main (argc=11, argv=0x7fffffffda78, envp=0x7fffffffdad8) at /root/git/qemu/vl.c:4557 Hope this helps. Thanks. -- Peter Xu