linux-kernel - Re: [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests

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Date:   Wed, 19 Dec 2018 15:21:49 +0000
From:   Peter Maydell <peter.maydell@...aro.org>
To:     Richard Henderson <richard.henderson@...aro.org>
Cc:     Kristina Martsenko <kristina.martsenko@....com>,
        lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jacob Bramley <jacob.bramley@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        awallis@...eaurora.org, Will Deacon <will.deacon@....com>,
        kvmarm@...ts.cs.columbia.edu, Cyrill Gorcunov <gorcunov@...il.com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
        amit.kachhap@....com, Dave P Martin <dave.martin@....com>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        keescook@...omium.org
Subject: Re: [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests

On Mon, 10 Dec 2018 at 20:22, Richard Henderson
<richard.henderson@...aro.org> wrote:
>
> On 12/10/18 2:12 PM, Kristina Martsenko wrote:
> > The plan was to disable trapping, yes. However, after that thread there
> > was a retrospective change applied to the architecture, such that the
> > XPACLRI (and XPACD/XPACI) instructions are no longer trapped by
> > HCR_EL2.API. (The public documentation on this has not been updated
> > yet.) This means that no HINT-space instructions should trap anymore.
>
> Ah, thanks for the update.  I'll update my QEMU patch set.

Just to follow up on this loose end, this change to HCR_EL2.API
trap behaviour is documented in the 00bet9 release of the system
register XML which came out today:
https://developer.arm.com/products/architecture/cpu-architecture/a-profile/exploration-tools/system-registers-for-armv8-a

thanks
-- PMM