On 06/19/2013 07:08 PM, Paolo Bonzini wrote: > Il 10/06/2013 19:03, Gleb Natapov ha scritto: >> On Mon, Jun 10, 2013 at 10:43:52PM +0900, Takuya Yoshikawa wrote: >>> On Mon, 10 Jun 2013 16:39:37 +0800 >>> Xiao Guangrong <xiaoguangrong.eric@xxxxxxxxx> wrote: >>> >>>> On 06/10/2013 03:56 PM, Gleb Natapov wrote: >>>>> On Fri, Jun 07, 2013 at 04:51:22PM +0800, Xiao Guangrong wrote: >>> >>>>> Looks good to me, but doesn't tis obsolete kvm_mmu_zap_mmio_sptes() and >>>>> sp->mmio_cached, so they should be removed as part of the patch series? >>>> >>>> Yes, i agree, they should be removed. :) >>> >>> I'm fine with removing it but please make it clear that you all agree >>> on the same basis. >>> >>> Last time, Paolo mentioned the possibility to use some bits of spte for >>> other things. The suggestion there was to keep sp->mmio_cached code >>> for the time we would need to reduce the bits for generation numbers. >>> >>> Do you think that zap_all() is now preemptible and can treat the >>> situation reasonably well as the current kvm_mmu_zap_mmio_sptes()? >>> >>> One downside is the need to zap unrelated shadow pages, but if this case >>> is really very rare, yes I agree, it should not be a problem: it depends >>> on how many bits we can use. >>> >>> Just please reconfirm. >>> >> That was me who mention the possibility to use some bits of spte for >> other things. But for now I have a use for one bit only. Now that you >> have reminded me about that discussion I am not so sure we want to >> remove kvm_mmu_zap_mmio_sptes(), but on the other hand it is non >> preemptable, so large number of mmio sptes can cause soft lockups. >> zap_all() is better in this regards now. > > I asked Gleb on IRC, and he's fine with applying patch 7 too (otherwise > there's hardly any benefit, because kvm_mmu_zap_mmio_sptes is > non-preemptable). > > I'm also changing the -13 to -150 since it's quite easy to generate 150 > calls to KVM_SET_USER_MEMORY_REGION. Using QEMU, and for a pretty basic > guest with virtio-net, IDE controller and VGA you get: > > - 9-10 calls before starting the guest, depending on the guest memory size > > - around 25 during the BIOS > > - around 20 during kernel boot > > - 34 during a single dump of the 64 KB ROM from a virtio-net device. Okay. The change is find to me. :) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
