linux-kernel - Re: [PATCH v4 00/11] KVM: Implement nested TSC scaling

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Message-ID: <cbb1272d6fc5713b5d53972ae55c1220f903595f.camel@amazon.com>
Date:   Tue, 15 Jun 2021 08:44:17 +0000
From:   "Stamatis, Ilias" <ilstam@...zon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>
CC:     "jmattson@...gle.com" <jmattson@...gle.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "mtosatti@...hat.com" <mtosatti@...hat.com>,
        "zamsden@...il.com" <zamsden@...il.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "mlevitsk@...hat.com" <mlevitsk@...hat.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>
Subject: Re: [PATCH v4 00/11] KVM: Implement nested TSC scaling

On Wed, 2021-05-26 at 19:44 +0100, Ilias Stamatis wrote:
> KVM currently supports hardware-assisted TSC scaling but only for L1;
> the feature is not exposed to nested guests. This patch series adds
> support for nested TSC scaling and allows both L1 and L2 to be scaled
> with different scaling factors. That is achieved by "merging" the 01 and
> 02 values together.
> 
> Most of the logic in this series is implemented in common code (by doing
> the necessary restructurings), however the patches add support for VMX
> only. Adding support for SVM should be easy at this point and Maxim
> Levitsky has volunteered to do this (thanks!).
> 
> Changelog:
> 
> Only patch 9 needs reviewing at this point, but I am re-sending the
> whole series as I also applied nitpicks suggested to some of the other
> pathces.
> 
> v4:
>   - Added vendor callbacks for writing the TSC multiplier
>   - Moved the VMCS multiplier writes from the VMCS load path to common
>     code that only gets called on TSC ratio changes
>   - Merged together patches 10 and 11 of v3
>   - Applied all nitpick-feedback of the previous versions
> 
> v3:
>   - Applied Sean's feedback
>   - Refactored patches 7 to 10
> 
> v2:
>   - Applied all of Maxim's feedback
>   - Added a mul_s64_u64_shr function in math64.h
>   - Added a separate kvm_scale_tsc_l1 function instead of passing an
>     argument to kvm_scale_tsc
>   - Implemented the 02 fields calculations in common code
>   - Moved all of write_l1_tsc_offset's logic to common code
>   - Added a check for whether the TSC is stable in patch 10
>   - Used a random L1 factor and a negative offset in patch 10
> 
> Ilias Stamatis (11):
>   math64.h: Add mul_s64_u64_shr()
>   KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch'
>   KVM: X86: Rename kvm_compute_tsc_offset() to
>     kvm_compute_l1_tsc_offset()
>   KVM: X86: Add a ratio parameter to kvm_scale_tsc()
>   KVM: nVMX: Add a TSC multiplier field in VMCS12
>   KVM: X86: Add functions for retrieving L2 TSC fields from common code
>   KVM: X86: Add functions that calculate the nested TSC fields
>   KVM: X86: Move write_l1_tsc_offset() logic to common code and rename
>     it
>   KVM: X86: Add vendor callbacks for writing the TSC multiplier
>   KVM: nVMX: Enable nested TSC scaling
>   KVM: selftests: x86: Add vmx_nested_tsc_scaling_test
> 
>  arch/x86/include/asm/kvm-x86-ops.h            |   5 +-
>  arch/x86/include/asm/kvm_host.h               |  15 +-
>  arch/x86/kvm/svm/svm.c                        |  35 ++-
>  arch/x86/kvm/vmx/nested.c                     |  33 ++-
>  arch/x86/kvm/vmx/vmcs12.c                     |   1 +
>  arch/x86/kvm/vmx/vmcs12.h                     |   4 +-
>  arch/x86/kvm/vmx/vmx.c                        |  55 ++--
>  arch/x86/kvm/vmx/vmx.h                        |  11 +-
>  arch/x86/kvm/x86.c                            | 114 +++++++--
>  include/linux/math64.h                        |  19 ++
>  tools/testing/selftests/kvm/.gitignore        |   1 +
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../kvm/x86_64/vmx_nested_tsc_scaling_test.c  | 242 ++++++++++++++++++
>  13 files changed, 451 insertions(+), 85 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
> 

Hello,

What is the status of these? I think all patches have been reviewed and
approved at this point.

(There's a new revision v6 of patch 9 that has been reviewed too)

Thanks,
Ilias