Any comments? Paolo! :) On Wed, 9 Sep 2020 at 11:04, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: > > Any comments? guys! > On Tue, 1 Sep 2020 at 19:52, <yulei.kernel@xxxxxxxxx> wrote: > > > > From: Yulei Zhang <yulei.kernel@xxxxxxxxx> > > > > Currently in KVM memory virtulization we relay on mmu_lock to > > synchronize the memory mapping update, which make vCPUs work > > in serialize mode and slow down the execution, especially after > > migration to do substantial memory mapping will cause visible > > performance drop, and it can get worse if guest has more vCPU > > numbers and memories. > > > > The idea we present in this patch set is to mitigate the issue > > with pre-constructed memory mapping table. We will fast pin the > > guest memory to build up a global memory mapping table according > > to the guest memslots changes and apply it to cr3, so that after > > guest starts up all the vCPUs would be able to update the memory > > simultaneously without page fault exception, thus the performance > > improvement is expected. > > > > We use memory dirty pattern workload to test the initial patch > > set and get positive result even with huge page enabled. For example, > > we create guest with 32 vCPUs and 64G memories, and let the vcpus > > dirty the entire memory region concurrently, as the initial patch > > eliminate the overhead of mmu_lock, in 2M/1G huge page mode we would > > get the job done in about 50% faster. > > > > We only validate this feature on Intel x86 platform. And as Ben > > pointed out in RFC V1, so far we disable the SMM for resource > > consideration, drop the mmu notification as in this case the > > memory is pinned. > > > > V1->V2: > > * Rebase the code to kernel version 5.9.0-rc1. > > > > Yulei Zhang (9): > > Introduce new fields in kvm_arch/vcpu_arch struct for direct build EPT > > support > > Introduce page table population function for direct build EPT feature > > Introduce page table remove function for direct build EPT feature > > Add release function for direct build ept when guest VM exit > > Modify the page fault path to meet the direct build EPT requirement > > Apply the direct build EPT according to the memory slots change > > Add migration support when using direct build EPT > > Introduce kvm module parameter global_tdp to turn on the direct build > > EPT mode > > Handle certain mmu exposed functions properly while turn on direct > > build EPT mode > > > > arch/mips/kvm/mips.c | 13 + > > arch/powerpc/kvm/powerpc.c | 13 + > > arch/s390/kvm/kvm-s390.c | 13 + > > arch/x86/include/asm/kvm_host.h | 13 +- > > arch/x86/kvm/mmu/mmu.c | 533 ++++++++++++++++++++++++++++++-- > > arch/x86/kvm/svm/svm.c | 2 +- > > arch/x86/kvm/vmx/vmx.c | 7 +- > > arch/x86/kvm/x86.c | 55 ++-- > > include/linux/kvm_host.h | 7 +- > > virt/kvm/kvm_main.c | 43 ++- > > 10 files changed, 639 insertions(+), 60 deletions(-) > > > > -- > > 2.17.1 > >
