On Mon, 2009-04-27 at 14:58 +0800, Liu Yu wrote: > Shadow tlb array costs a lot memory > and incurs potential coherence problem. > > Remove it and we now translate to shadow mappings directly > from guest TLB entries. > > Signed-off-by: Liu Yu <yu.liu@xxxxxxxxxxxxx> Well, funny story... pretty much as soon as we removed the shadow TLB on 440, we put it back. But we use it differently now. Our experience on 440 was that it was a performance win to *also* keep a shadow TLB array, but use that *only* in the vcpu_put/vcpu_load() path instead of tlbia(). In other words, instead of just clearing all that guest TLB state you worked so hard to build up, preserve it across host context switches. We don't use that array for anything other than host context switches. For normal exits (handled in kernel or handled in qemu) we take a less precise "shadowy" approach, where host and guest TLB entries can compete without KVM's knowledge, and we indiscriminately invalidate them. (Yes, http://www.linux-kvm.org/page/PowerPC_Book_E_MMU is no longer completely accurate.) I'm not sure what the coherence problems are that you allude to, but we never did SMP host support for 440. -- Hollis Blanchard IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
