linux-kernel - Re: [PATCH v6 0/3] Introduce Notify VM exit

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Message-ID: <634e2d2c-6d81-f884-67f0-10246b76234d@intel.com>
Date:   Fri, 6 May 2022 10:43:35 +0800
From:   Chenyi Qiang <chenyi.qiang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.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: [PATCH v6 0/3] Introduce Notify VM exit

Kindly ping for the comments.

On 4/21/2022 3:29 PM, Chenyi Qiang wrote:
> Virtual machines can exploit Intel ISA characterstics to cause
> functional denial of service to the VMM. This series introduces a new
> feature named Notify VM exit, which can help mitigate such kind of
> attacks.
> 
> Patch 1: An extension of KVM_SET_VCPU_EVENTS ioctl to inject a
> synthesized shutdown event from user space. This is also a fix for other
> synthesized triple fault, e.g. the RSM patch or nested_vmx_abort(),
> which could get lost when exit to userspace to do migrate.
> 
> Patch 2: A selftest about get/set triple fault event.
> 
> Patch 3: The main patch to enable Notify VM exit.
> 
> ---
> Change logs:
> v5 -> v6
> - Do some changes in document.
> - Add a selftest about get/set triple fault event. (Sean)
> - extend the argument to include both the notify window and some flags
>    when enabling KVM_CAP_X86_BUS_LOCK_EXIT CAP. (Sean)
> - Change to use KVM_VCPUEVENT_VALID_TRIPE_FAULT in flags field and add
>    pending_triple_fault field in struct kvm_vcpu_events, which allows
>    userspace to make/clear triple fault request. (Sean)
> - Add a flag in kvm_x86_ops to avoid the kvm_has_notify_vmexit global
>    varialbe and its export.(Sean)
> - v5: https://lore.kernel.org/lkml/20220318074955.22428-1-chenyi.qiang@intel.com/
> 
> v4 -> v5
> - rename KVM_VCPUEVENTS_SHUTDOWN to KVM_VCPUEVENTS_TRIPLE_FAULT. Make it
>    bidirection and add it to get_vcpu_events. (Sean)
> - v4: https://lore.kernel.org/all/20220310084001.10235-1-chenyi.qiang@intel.com/
> 
> v3 -> v4
> - Change this feature to per-VM scope. (Jim)
> - Once VM_CONTEXT_INVALID set in exit_qualification, exit to user space
>    notify this fatal case, especially the notify VM exit happens in L2.
>    (Jim)
> - extend KVM_SET_VCPU_EVENTS to allow user space to inject a shutdown
>    event. (Jim)
> - A minor code changes.
> - Add document for the new KVM capability.
> - v3: https://lore.kernel.org/lkml/20220223062412.22334-1-chenyi.qiang@intel.com/
> 
> v2 -> v3
> - add a vcpu state notify_window_exits to record the number of
>    occurence as well as a pr_warn output. (Sean)
> - Add the handling in nested VM to prevent L1 bypassing the restriction
>    through launching a L2. (Sean)
> - Only kill L2 when L2 VM is context invalid, synthesize a
>    EXIT_REASON_TRIPLE_FAULT to L1 (Sean)
> - To ease the current implementation, make module parameter
>    notify_window read-only. (Sean)
> - Disable notify window exit by default.
> - v2: https://lore.kernel.org/lkml/20210525051204.1480610-1-tao3.xu@intel.com/
> 
> v1 -> v2
> - Default set notify window to 0, less than 0 to disable.
> - Add more description in commit message.
> ---
> 
> Chenyi Qiang (2):
>    KVM: X86: Save&restore the triple fault request
>    KVM: selftests: Add a test to get/set triple fault event
> 
> Tao Xu (1):
>    KVM: VMX: Enable Notify VM exit
> 
>   Documentation/virt/kvm/api.rst                | 55 +++++++++++
>   arch/x86/include/asm/kvm_host.h               |  9 ++
>   arch/x86/include/asm/vmx.h                    |  7 ++
>   arch/x86/include/asm/vmxfeatures.h            |  1 +
>   arch/x86/include/uapi/asm/kvm.h               |  4 +-
>   arch/x86/include/uapi/asm/vmx.h               |  4 +-
>   arch/x86/kvm/vmx/capabilities.h               |  6 ++
>   arch/x86/kvm/vmx/nested.c                     |  8 ++
>   arch/x86/kvm/vmx/vmx.c                        | 48 +++++++++-
>   arch/x86/kvm/x86.c                            | 33 ++++++-
>   arch/x86/kvm/x86.h                            |  5 +
>   include/uapi/linux/kvm.h                      | 10 ++
>   tools/testing/selftests/kvm/.gitignore        |  1 +
>   tools/testing/selftests/kvm/Makefile          |  1 +
>   .../kvm/x86_64/triple_fault_event_test.c      | 96 +++++++++++++++++++
>   15 files changed, 280 insertions(+), 8 deletions(-)
>   create mode 100644 tools/testing/selftests/kvm/x86_64/triple_fault_event_test.c
>