linux-kernel - Re: [RESEND RFC v2 0/2] add bus lock VM exit support

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Message-ID: <28b3864d-8cc2-a062-5d29-4f92dce74630@intel.com>
Date:   Wed, 26 Aug 2020 17:57:45 +0800
From:   Chenyi Qiang <chenyi.qiang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND RFC v2 0/2] add bus lock VM exit support

Ping for comments

On 8/17/2020 11:36 AM, Chenyi Qiang wrote:
> Resend to rebase on 5.9-rc1.
> 
> ---
> 
> Add the support for bus lock VM exit in KVM. It is a sub-feature of bus
> lock detection. Another sub-feature named bus lock debug exception is
> blocked due to requirement to rework the HW design:
> https://lore.kernel.org/lkml/87r1stmi1x.fsf@nanos.tec.linutronix.de/
> 
> In this patch series, the first patch applies Sean's refactor to
> vcpu_vmx.exit_reason available at
> https://patchwork.kernel.org/patch/11500659.
> It is necessary as bus lock VM exit adds a new modifier bit(bit 26) in
> exit_reason field in VMCS.
> 
> The second patch is the enabling work for bus lock VM exit. Add the
> support to set the capability to enable bus lock vm exit. The current
> implementation just exit to user space when handling the bus lock
> detected in guest.
> 
> The concrete throttling policy in user space still needs to be
> discussed. We can enforce ratelimit on bus lock in guest, just inject
> some sleep time, or any other ideas?
> 
> Document for Bus Lock Detection is now available at the latest "Intel
> Architecture Instruction Set Extensions Programming Reference".
> 
> Document Link:
> https://software.intel.com/content/www/us/en/develop/download/intel-architecture-instruction-set-extensions-programming-reference.html
> 
> 
> v1->v2 Changelogs:
> - resolve Vitaly's comment to introduce the KVM_EXIT_BUS_LOCK and a
>    capability to enable it.
> - add the support to exit to user space when handling bus locks.
> - extend the vcpu->run->flags to indicate bus lock detected for other
>    exit reasons when exiting to user space.
> 
> Chenyi Qiang (1):
>    KVM: VMX: Enable bus lock VM exit
> 
> Sean Christopherson (1):
>    KVM: VMX: Convert vcpu_vmx.exit_reason to a union
> 
>   arch/x86/include/asm/kvm_host.h    |  9 +++
>   arch/x86/include/asm/vmx.h         |  1 +
>   arch/x86/include/asm/vmxfeatures.h |  1 +
>   arch/x86/include/uapi/asm/kvm.h    |  1 +
>   arch/x86/include/uapi/asm/vmx.h    |  4 +-
>   arch/x86/kvm/vmx/capabilities.h    |  6 ++
>   arch/x86/kvm/vmx/nested.c          | 42 ++++++++-----
>   arch/x86/kvm/vmx/vmx.c             | 97 ++++++++++++++++++++----------
>   arch/x86/kvm/vmx/vmx.h             | 25 +++++++-
>   arch/x86/kvm/x86.c                 | 36 ++++++++++-
>   arch/x86/kvm/x86.h                 |  5 ++
>   include/uapi/linux/kvm.h           |  2 +
>   12 files changed, 179 insertions(+), 50 deletions(-)
>