On Fri, 2007-11-30 at 18:03 +0800, Zhang, Xiantao wrote: > Avi Kivity wrote: > > Zhang, Xiantao wrote: > >>>> > >>> Ah, I see. It isn't just the alignment. How do you allocate > >>> kvm_vcpu, then? > >>> > >> > >> For evevy vm, we allocate a big chunk of memory for structure > >> allocation. For vcpu, it should be always 64k aligned through our > >> allocation mechanism. So, we don't care about its aligment issue :) > >> > > > > I see. Can you explain why you do that? Do you have a special > > allocator in your guest-resident vmm module? > > Since our VMM module and KVM module will share the kvm and vcpu > structure, but VMM module has a different address space, so we have to > use fixed allocation method to handle this share. For example, we > allocates 1M memory(1M align) for every vm for this purpose in kvm > module, and the first 64k is used for first vcpu of guest, and the > second 64 for the second vcpu, and same for other vcpus. You can call > it as special allocator or other names:) This is determined by IA64 > virtualization architecture, and hard to workaround it in this > host-based vm model. :(
We're doing something similar with very large allocations. Currently, PowerPC's "vcpu" is actually a copy of the exception handlers, plus the real vcpu data structure at a higher offset. Since our exception handlers can't span 64KB regions, we allocate a full 64KB for each vcpu. I'm not sure what benefit a kmem_cache would have in this situation... -- Hollis Blanchard IBM Linux Technology Center ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
