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

From: Vitaly Kuznetsov
Date: Fri Jun 11 2021 - 05:44:43 EST

Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes:

> On Thu, 2021-06-10 at 17:17 +0200, Paolo Bonzini wrote:
>> 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@xxxxxxxxxx/
>> >
>> > 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
>>
>
> Hi!
>
> This patch series causes a build failure here:
>
> arch/x86/kvm/vmx/vmx.c: In function ‘hardware_setup’:
> arch/x86/kvm/vmx/vmx.c:7752:34: error: ‘hv_remote_flush_tlb’ undeclared (first use in this function)
> 7752 | vmx_x86_ops.tlb_remote_flush = hv_remote_flush_tlb;
> | ^~~~~~~~~~~~~~~~~~~
> arch/x86/kvm/vmx/vmx.c:7752:34: note: each undeclared identifier is reported only once for each function it appears in
> arch/x86/kvm/vmx/vmx.c:7754:5: error: ‘hv_remote_flush_tlb_with_range’ undeclared (first use in this function)
> 7754 | hv_remote_flush_tlb_with_range;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> Also this:
>
> arch/x86/kvm/vmx/vmx.c: In function ‘hardware_setup’:
> arch/x86/kvm/vmx/vmx.c:7752:34: error: ‘hv_remote_flush_tlb’ undeclared (first use in this function)
> 7752 | vmx_x86_ops.tlb_remote_flush = hv_remote_flush_tlb;
> | ^~~~~~~~~~~~~~~~~~~
> arch/x86/kvm/vmx/vmx.c:7752:34: note: each undeclared identifier is reported only once for each function it appears in
> arch/x86/kvm/vmx/vmx.c:7754:5: error: ‘hv_remote_flush_tlb_with_range’ undeclared (first use in this function)
> 7754 | hv_remote_flush_tlb_with_range;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>

Yea, reported already:

https://lore.kernel.org/kvm/683fa50765b29f203cb4b0953542dc43226a7a2f.camel@xxxxxxxxxx/T/#mf732ba9567923d800329f896761e4ee104475894

>
> Best regards,
> Maxim Levitsky
>

--
Vitaly