linux-kernel - Re: [PATCH v4 1/7] x86/cpu: Define a scattered No Nested Data Breakpoints feature bit

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Message-ID: <f2964d1c-ecb9-f88b-c73e-64c960b91d9a@amd.com>
Date:   Mon, 5 Dec 2022 16:05:17 -0600
From:   Kim Phillips <kim.phillips@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, Babu Moger <Babu.Moger@....com>,
        Borislav Petkov <bp@...e.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Alexey Kardashevskiy <aik@....com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/7] x86/cpu: Define a scattered No Nested Data
 Breakpoints feature bit

On 12/5/22 2:20 PM, Borislav Petkov wrote:
> On Mon, Dec 05, 2022 at 11:32:01AM -0600, Kim Phillips wrote:
>> This is starting to get off-topic.
> 
> What does that mean?
> 
> Are you saying I'm not allowed to ask why stuff is added?

No, sorry.  You had asked "what is the use of this bit in
a KVM guest?", and I'm saying that it was already being
propagated to the guest prior to this patchseries, which
is about propagating the Automatic IBRS feature.  That's
all.

Thanks,

Kim