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. Paolo -- 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
