On Tue, Sep 17, 2019 at 11:28 PM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>
> Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
>
> > On 22/08/19 16:30, lantianyu1986@xxxxxxxxx wrote:
> >> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> >>
> >> This patchset is to add Hyper-V direct tlb support in KVM. Hyper-V
> >> in L0 can delegate L1 hypervisor to handle tlb flush request from
> >> L2 guest when direct tlb flush is enabled in L1.
> >>
> >> Patch 2 introduces new cap KVM_CAP_HYPERV_DIRECT_TLBFLUSH to enable
> >> feature from user space. User space should enable this feature only
> >> when Hyper-V hypervisor capability is exposed to guest and KVM profile
> >> is hided. There is a parameter conflict between KVM and Hyper-V hypercall.
> >> We hope L2 guest doesn't use KVM hypercall when the feature is
> >> enabled. Detail please see comment of new API "KVM_CAP_HYPERV_DIRECT_TLBFLUSH"
> >>
> >> Change since v3:
> >> - Update changelog in each patches.
> >>
> >> Change since v2:
> >> - Move hv assist page(hv_pa_pg) from struct kvm to struct kvm_hv.
> >>
> >> Change since v1:
> >> - Fix offset issue in the patch 1.
> >> - Update description of KVM KVM_CAP_HYPERV_DIRECT_TLBFLUSH.
> >>
> >> Tianyu Lan (2):
> >> x86/Hyper-V: Fix definition of struct hv_vp_assist_page
> >> KVM/Hyper-V: Add new KVM capability KVM_CAP_HYPERV_DIRECT_TLBFLUSH
> >>
> >> Vitaly Kuznetsov (1):
> >> KVM/Hyper-V/VMX: Add direct tlb flush support
> >>
> >> Documentation/virtual/kvm/api.txt | 13 +++++++++++++
> >> arch/x86/include/asm/hyperv-tlfs.h | 24 ++++++++++++++++++-----
> >> arch/x86/include/asm/kvm_host.h | 4 ++++
> >> arch/x86/kvm/vmx/evmcs.h | 2 ++
> >> arch/x86/kvm/vmx/vmx.c | 39 ++++++++++++++++++++++++++++++++++++++
> >> arch/x86/kvm/x86.c | 8 ++++++++
> >> include/uapi/linux/kvm.h | 1 +
> >> 7 files changed, 86 insertions(+), 5 deletions(-)
> >>
> >
> > Queued, thanks.
> >
>
> I had a suggestion how we can get away without the new capability (like
> direct tlb flush gets automatically enabled when Hyper-V hypercall page
> is activated and we know we can't handle KVM hypercalls any more)
> but this can probably be done as a follow-up.
>
Hi Vital'y：
Actually, I have tried your proposal but it turns out
KVM in L1 fails to
enable direct tlb flush most time after nested VM starts.
"hv_enlightenments_control.
nested_flush_hypercall" flag in evmcs is cleared by Hyper-V after run
nested VM. I still
wait answer from Hyper-V team. So far, it looks like enabling direct
tlb flush before start
nested VM is a safe way.Once get more infomration from Hyper-V team and we may
have a look to how to enable your proposal.
--
Best regards
Tianyu Lan
