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From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oupton@google.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <Alexandru.Elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Andrew Jones <drjones@redhat.com>,
	Peter Shier <pshier@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>
Subject: Re: [PATCH 3/3] KVM: arm64: Raise KVM's reported debug architecture to v8.2
Date: Mon, 01 Nov 2021 10:21:23 +0000	[thread overview]
Message-ID: <87bl349nx8.wl-maz@kernel.org> (raw)
In-Reply-To: <CAOQ_QshjMXMFK2uHVDxYbFkVJApGxhT4M4NbMNY+qX3QvPe5_A@mail.gmail.com>

On Fri, 29 Oct 2021 19:18:13 +0100,
Oliver Upton <oupton@google.com> wrote:
> 
> Hey Marc,
> 
> On Fri, Oct 29, 2021 at 4:31 AM Marc Zyngier <maz@kernel.org> wrote:
> >
> > On Fri, 29 Oct 2021 01:32:02 +0100,
> > Oliver Upton <oupton@google.com> wrote:
> [...]
> > >       case SYS_ID_AA64DFR0_EL1:
> > > -             /* Limit debug to ARMv8.0 */
> > > +             /* Limit debug to ARMv8.2 */
> > >               val &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER);
> > > -             val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), 6);
> > > +             val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), 8);
> > > +
> > > +             /* Hide DoubleLock from guests */
> > > +             val &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_DOUBLELOCK);
> > > +             val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DOUBLELOCK), 0CF);
> > > +
> >
> > One issue with that is that this will break migration from an older
> > kernel (DFR0 will be different between source and destination).
> >
> > You'll need a set_user handler and deal with it in a similar way to
> > CSV2/CSV3.
> 
> Yeah, definitely so. In that case, unless we're strongly motivated to
> expose these changes soon, I'll just punt the ID register changes
> until Reiji's series [1] lands, as anything I add for a writable DFR0
> will invariably be scrapped in favor of his work.

Yeah, I think that's a sensible thing to do. I need to find the
bandwidth to look into these patches...

> I'll post v2 of this series folding in your feedback (thx for quick
> review, btw), less this patch.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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      reply	other threads:[~2021-11-01 10:22 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-29  0:31 [PATCH 0/3] KVM: arm64: Fixes for the exposed debug architecture Oliver Upton
2021-10-29  0:32 ` [PATCH 1/3] KVM: arm64: Stash OSLSR_EL1 in the cpu context Oliver Upton
2021-10-29 11:27   ` Marc Zyngier
2021-10-29  0:32 ` [PATCH 2/3] KVM: arm64: Allow the guest to change the OS Lock status Oliver Upton
2021-10-29 11:16   ` Marc Zyngier
2021-10-29  0:32 ` [PATCH 3/3] KVM: arm64: Raise KVM's reported debug architecture to v8.2 Oliver Upton
2021-10-29 11:31   ` Marc Zyngier
2021-10-29 18:18     ` Oliver Upton
2021-11-01 10:21       ` Marc Zyngier [this message]

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