linux-kernel - Re: [PATCH v5 0/7] Hyper-V nested virt enlightenments for SVM

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Date:   Thu, 10 Jun 2021 17:17:02 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vineeth Pillai <viremana@...ux.microsoft.com>,
        Lan Tianyu <Tianyu.Lan@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Wei Liu <wei.liu@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "K. Y. Srinivasan" <kys@...rosoft.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org
Subject: Re: [PATCH v5 0/7] Hyper-V nested virt enlightenments for SVM

On 03/06/21 17:14, Vineeth Pillai wrote:
> This patch series enables the nested virtualization enlightenments for
> SVM. This is very similar to the enlightenments for VMX except for the
> fact that there is no enlightened VMCS. For SVM, VMCB is already an
> architectural in-memory data structure.
> 
> Note: v5 is just a rebase on hyperv-next(5.13-rc1) and needed a rework
> based on the patch series: (KVM: VMX: Clean up Hyper-V PV TLB flush)
> https://lore.kernel.org/lkml/20210305183123.3978098-1-seanjc@google.com/
> 
> The supported enlightenments are:
> 
> Enlightened TLB Flush: If this is enabled, ASID invalidations invalidate
> only gva -> hpa entries. To flush entries derived from NPT, hyper-v
> provided hypercalls (HvFlushGuestPhysicalAddressSpace or
> HvFlushGuestPhysicalAddressList) should be used.
> 
> Enlightened MSR bitmap(TLFS 16.5.3): "When enabled, L0 hypervisor does
> not monitor the MSR bitmaps for changes. Instead, the L1 hypervisor must
> invalidate the corresponding clean field after making changes to one of
> the MSR bitmaps."
> 
> Direct Virtual Flush(TLFS 16.8): The hypervisor exposes hypercalls
> (HvFlushVirtualAddressSpace, HvFlushVirtualAddressSpaceEx,
> HvFlushVirtualAddressList, and HvFlushVirtualAddressListEx) that allow
> operating systems to more efficiently manage the virtual TLB. The L1
> hypervisor can choose to allow its guest to use those hypercalls and
> delegate the responsibility to handle them to the L0 hypervisor. This
> requires the use of a partition assist page."
> 
> L2 Windows boot time was measured with and without the patch. Time was
> measured from power on to the login screen and was averaged over a
> consecutive 5 trials:
>    Without the patch: 42 seconds
>    With the patch: 29 seconds
> --
> 
> Changes from v4
> - Rebased on top of 5.13-rc1 and reworked based on the changes in the
>    patch series: (KVM: VMX: Clean up Hyper-V PV TLB flush)
>    
> Changes from v3
> - Included definitions for software/hypervisor reserved fields in SVM
>    architectural data structures.
> - Consolidated Hyper-V specific code into svm_onhyperv.[ch] to reduce
>    the "ifdefs". This change applies only to SVM, VMX is not touched and
>    is not in the scope of this patch series.
> 
> Changes from v2:
> - Refactored the Remote TLB Flush logic into separate hyperv specific
>    source files (kvm_onhyperv.[ch]).
> - Reverted the VMCB Clean bits macro changes as it is no longer needed.
> 
> Changes from v1:
> - Move the remote TLB flush related fields from kvm_vcpu_hv and kvm_hv
>    to kvm_vcpu_arch and kvm_arch.
> - Modify the VMCB clean mask runtime based on whether L1 hypervisor
>    is running on Hyper-V or not.
> - Detect Hyper-V nested enlightenments based on
>    HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS.
> - Address other minor review comments.
> ---
> 
> Vineeth Pillai (7):
>    hyperv: Detect Nested virtualization support for SVM
>    hyperv: SVM enlightened TLB flush support flag
>    KVM: x86: hyper-v: Move the remote TLB flush logic out of vmx
>    KVM: SVM: Software reserved fields
>    KVM: SVM: hyper-v: Remote TLB flush for SVM
>    KVM: SVM: hyper-v: Enlightened MSR-Bitmap support
>    KVM: SVM: hyper-v: Direct Virtual Flush support
> 
>   arch/x86/include/asm/hyperv-tlfs.h |   9 ++
>   arch/x86/include/asm/kvm_host.h    |   9 ++
>   arch/x86/include/asm/svm.h         |   9 +-
>   arch/x86/include/uapi/asm/svm.h    |   3 +
>   arch/x86/kernel/cpu/mshyperv.c     |  10 ++-
>   arch/x86/kvm/Makefile              |   9 ++
>   arch/x86/kvm/kvm_onhyperv.c        |  93 +++++++++++++++++++++
>   arch/x86/kvm/kvm_onhyperv.h        |  32 +++++++
>   arch/x86/kvm/svm/svm.c             |  14 ++++
>   arch/x86/kvm/svm/svm.h             |  22 ++++-
>   arch/x86/kvm/svm/svm_onhyperv.c    |  41 +++++++++
>   arch/x86/kvm/svm/svm_onhyperv.h    | 129 +++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/vmx.c             | 105 +----------------------
>   arch/x86/kvm/vmx/vmx.h             |   9 --
>   arch/x86/kvm/x86.c                 |   9 ++
>   15 files changed, 384 insertions(+), 119 deletions(-)
>   create mode 100644 arch/x86/kvm/kvm_onhyperv.c
>   create mode 100644 arch/x86/kvm/kvm_onhyperv.h
>   create mode 100644 arch/x86/kvm/svm/svm_onhyperv.c
>   create mode 100644 arch/x86/kvm/svm/svm_onhyperv.h
> 

Queued, thanks.

Paolo