Re: [Qemu-devel] qemu memory manage question

[李强]

> -----Original Message-----
> From: Qemu-devel
> [mailto:address@hidden On Behalf Of
> jack.chen
> Sent: Monday, April 17, 2017 6:56 PM
> To: Peter Xu
> Cc: qemu
> Subject: Re: [Qemu-devel] qemu memory manage question
> 
> 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!
> 

They are callbacks.
Every change of memory topology will call these listeners, add 
subregion(Peter's example),
modify the property of memory, create address space for example. 

Thanks.

--
Li Qiang /the Gear Team, Qihoo 360 Inc


> 2017-04-17 18:26 GMT+08:00 Peter Xu <address@hidden>:
> > 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