linux-kernel - Re: [PATCH 3/3] KVM: SVM: allow to intercept all exceptions for debug

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Message-ID: <YFMbLWLlGgbOJuN/@8bytes.org>
Date:   Thu, 18 Mar 2021 10:19:41 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Kieran Bingham <kbingham@...nel.org>,
        Jessica Yu <jeyu@...nel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH 3/3] KVM: SVM: allow to intercept all exceptions for debug

On Tue, Mar 16, 2021 at 12:51:20PM +0200, Maxim Levitsky wrote:
> I agree but what is wrong with that? 
> This is a debug feature, and it only can be enabled by the root,
> and so someone might actually want this case to happen
> (e.g to see if a SEV guest can cope with extra #VC exceptions).

That doesn't make sense, we know that and SEV-ES guest can't cope with
extra #VC exceptions, so there is no point in testing this. It is more a
way to shot oneself into the foot for the user and a potential source of
bug reports for SEV-ES guests.


> I have nothing against not allowing this for SEV-ES guests though.
> What do you think?

I think SEV-ES guests should only have the intercept bits set which
guests acutally support.

Regards,

	Joerg