linux-kernel - Re: [PATCH v2 8/9] KVM: x86: add force_intercept_exceptions

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Date:   Tue, 27 Apr 2021 13:38:40 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        open list <linux-kernel@...r.kernel.org>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Jonathan Corbet <corbet@....net>, Jessica Yu <jeyu@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Will Deacon <will@...nel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Joerg Roedel <joro@...tes.org>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Jim Mattson <jmattson@...gle.com>,
        Cornelia Huck <cohuck@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "open list:S390" <linux-s390@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Kieran Bingham <kbingham@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <linux-arm-kernel@...ts.infradead.org>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH v2 8/9] KVM: x86: add force_intercept_exceptions_mask

On Thu, Apr 01, 2021 at 04:54:50PM +0300, Maxim Levitsky wrote:
> This parameter will be used by VMX and SVM code to force
> interception of a set of exceptions, given by a bitmask
> for guest debug and/or kvm debug.
> 
> This option is not intended for production.
> 
> This is based on an idea first shown here:
> https://patchwork.kernel.org/project/kvm/patch/20160301192822.GD22677@pd.tnic/
> 
> CC: Borislav Petkov <bp@...e.de>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 3 +++
>  arch/x86/kvm/x86.h | 2 ++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3627ce8fe5bb..1a51031d64d8 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -176,6 +176,9 @@ module_param(force_emulation_prefix, bool, S_IRUGO);
>  int __read_mostly pi_inject_timer = -1;
>  module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);
>  
> +uint force_intercept_exceptions_mask;
> +module_param(force_intercept_exceptions_mask, uint, S_IRUGO | S_IWUSR);
> +EXPORT_SYMBOL_GPL(force_intercept_exceptions_mask);

That's nice.

I could use some text explaning the usage though, i.e. that thing takes
a bitfield of exception vectors, so that I don't have to look at the
code each time. :-)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette