linux-kernel - Re: [PATCH 0/9] x86/virt: KVM: x86: Exception handling fixes/cleanups

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Date:   Wed, 27 Jan 2021 18:26:11 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "David P . Reed" <dpreed@...pplum.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Uros Bizjak <ubizjak@...il.com>
Subject: Re: [PATCH 0/9] x86/virt: KVM: x86: Exception handling fixes/cleanups

On 31/12/20 01:26, Sean Christopherson wrote:
> This series is a conglomeration of three previous series/patches and a bit
> of new code.  None of the previous series are directly related, but they
> are all needed to achieve the overarching goal of nuking
> __kvm_handle_fault_on_reboot(), which is a rather ugly inline asm macro
> that has the unfortunate side effect of inserting in-line JMP+CALL
> sequences.
> 
> Patches 1-3 are resurrected from a series by David Reed[1] to fix VMXOFF
> bugs in the reboot flows.
> 
> Patch 4 is a patch from Uros Bizjak to get rid of custom inline asm in
> nested VMX.  This already received Paolo's "Queued, thanks." blessing,
> but has not been pushed to kvm.git.  It's included here as there is an
> indirect dependency in patch 8.
> 
> Patches 5-6 are minor tweaks to KVM's VMX{ON/OFF} paths to use the
> kernel's now-fault-tolerant VMXOFF instead of KVM's custom asm.
> 
> Patch 7 replaces SVM's __ex()/__kvm_handle_fault_on_reboot() with more
> tailored asm goto macros, similar to the existing VMX asm_vmx*() macros.
> This is largely an excuse to get rid of __kvm_handle_fault_on_reboot();
> the actual benefits of removing JMP+CALL are likely negligible as SVM only
> has a few uses of the macro (versus VMX's bajillion VMREADs/VMWRITEs).
> 
> Patch 8 removes __ex()/__kvm_handle_fault_on_reboot().
> 
> Patch 9 is a very trimmed down version of a different patch from Uros[3],
> which cleaned up the __ex()/__kvm_handle_fault_on_reboot() code, as
> opposed to zapping them entirely.
> 
> [1] https://lkml.kernel.org/r/20200704203809.76391-1-dpreed@deepplum.com
> [2] https://lkml.kernel.org/r/20201029134145.107560-1-ubizjak@gmail.com
> [3] https://lkml.kernel.org/r/20201221194800.46962-1-ubizjak@gmail.com
> 
> David P. Reed (1):
>    x86/virt: Mark flags and memory as clobbered by VMXOFF
> 
> Sean Christopherson (6):
>    x86/virt: Eat faults on VMXOFF in reboot flows
>    x86/reboot: Force all cpus to exit VMX root if VMX is supported
>    KVM: VMX: Move Intel PT shenanigans out of VMXON/VMXOFF flows
>    KVM: VMX: Use the kernel's version of VMXOFF
>    KVM: SVM: Use asm goto to handle unexpected #UD on SVM instructions
>    KVM: x86: Kill off __ex() and __kvm_handle_fault_on_reboot()
> 
> Uros Bizjak (2):
>    KVM/nVMX: Use __vmx_vcpu_run in nested_vmx_check_vmentry_hw
>    KVM: x86: Move declaration of kvm_spurious_fault() to x86.h
> 
>   arch/x86/include/asm/kvm_host.h | 25 --------------
>   arch/x86/include/asm/virtext.h  | 25 ++++++++++----
>   arch/x86/kernel/reboot.c        | 30 ++++++-----------
>   arch/x86/kvm/svm/sev.c          |  5 ++-
>   arch/x86/kvm/svm/svm.c          | 18 +---------
>   arch/x86/kvm/svm/svm_ops.h      | 59 +++++++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/nested.c       | 32 ++----------------
>   arch/x86/kvm/vmx/vmenter.S      |  2 +-
>   arch/x86/kvm/vmx/vmx.c          | 28 ++++++----------
>   arch/x86/kvm/vmx/vmx.h          |  1 +
>   arch/x86/kvm/vmx/vmx_ops.h      |  4 +--
>   arch/x86/kvm/x86.c              |  9 ++++-
>   arch/x86/kvm/x86.h              |  2 ++
>   13 files changed, 117 insertions(+), 123 deletions(-)
>   create mode 100644 arch/x86/kvm/svm/svm_ops.h
> 

Queued, thanks.

Paolo