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Date: Thu, 27 Oct 2022 13:01:03 +0100
From: Mark Brown <broonie@kernel.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>,
	Vincent Donnefort <vdonnefort@google.com>, kvmarm@lists.linux.dev,
	catalin.marinas@arm.com, will@kernel.org,
	Richard Henderson <richard.henderson@linaro.org>
Subject: Re: Hang with nVHE mode and SME
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On Thu, Oct 27, 2022 at 10:44:39AM +0100, Peter Maydell wrote:
> On Wed, 26 Oct 2022 at 17:34, Mark Brown <broonie@kernel.org> wrote:
> > On Wed, Oct 26, 2022 at 05:13:46PM +0100, Marc Zyngier wrote:

> > > So the question is whether we work around this in the kernel (not
> > > enabling either KVM or SME if FEAT_FGT is not present), or leave it as
> > > is with the hope that QEMU gets updated.

> > > I'm inclined to do the latter. Thoughts anyone?

> Is the "kernel needs FEAT_FGT here" requirement a strong "the design
> just means it's kind of expected" one, or a weak "the features
> aren't really strongly tied together, it would be easy to do without"
> one?

We need it for nVHE mode since we need nTPIDR2_EL0 to trap access to
TPIDR2_EL0, in VHE mode this is controlled by SCTLR_EL2.EnTP2.  Looking
again I need to double check but I think I missed control of nSMPRI_EL1
which will be needed in both VHE and nVHE cases to trap access to
SMPRI_EL1, that's not controlled by the overall SME enable.

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