Re: [Qemu-devel] qemu memory manage question

From: "jack.chen" <zhunxun@gmail.com>
To: Peter Xu <peterx@redhat.com>
Cc: qemu <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] qemu memory manage question
Date: Mon, 17 Apr 2017 18:55:40 +0800	[thread overview]
Message-ID: <CADUDsAqnRJDhYcu2nR-zk5fkJDQ8GKkR7GjO-MrAEiJTt_X+oA@mail.gmail.com> (raw)
In-Reply-To: <20170417102607.GE16703@pxdev.xzpeter.org>

Thanks,from the path you have list to me,it can be  well explained,but
according to the source code,in the end of
kvm_init,kvm_memory_listener and  kvm_io_listener were registered by
memory_listener_register(),and  in the end of
memory_listener_register(),listener_add_address_space() was called for
each address_space,so the listener->region_add was executed then.I do
not know what mistake I have made,can you explain it to me ?? thank
you very much!

2017-04-17 18:26 GMT+08:00 Peter Xu <peterx@redhat.com>:
> 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 <address_space_memory>, old_view=0x5555567a7090, new_view=0x5555568d3460, adding=true) at /root/git/qemu/memory.c:871
> #2  0x00005555557c19f3 in address_space_update_topology (as=0x55555629e240 <address_space_memory>) 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