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From: Richard Henderson <richard.henderson@linaro.org>
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Date: Sun, 4 Nov 2018 09:50:29 +0000
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Subject: Re: [Qemu-devel] [PATCH v2 0/5] target/arm: KVM vs ARMISARegisters
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To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>, Peter Maydell <peter.maydell@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, qemu-arm <qemu-arm@nongnu.org>, Dave Martin <Dave.Martin@arm.com>

On 11/3/18 12:32 PM, Marc Zyngier wrote:
> We actively hide the LORegion feature from the guest since
> cc33c4e20185a391766ed5e78e2acc97e17ba511 (in the 4.17 time frame), so
> you shouldn't be able to obtain these on a recent host.

I don't think that patch is ideal.

In particular, LOR is a mandatory requirement of ARMv8.1.
The OS can rightly presume it is present in context.

Better, I think, is to trap the LOR registers, as you are doing,
and have them act as RAZ/WI.  This indicates, via LORID_EL1, that
there are zero supported LO regions, which is a valid ARMv8.1
configuration.


r~