linux-kernel - Re: [RFC 5/8] KVM: arm64: Explicitly handle MDSELR

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Message-ID: <86a5m8t8s6.wl-maz@kernel.org>
Date: Fri, 05 Apr 2024 11:15:37 +0100
From: Marc Zyngier <maz@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
	Jonathan Corbet <corbet@....net>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 5/8] KVM: arm64: Explicitly handle MDSELR_EL1 traps as UNDEFINED

On Fri, 05 Apr 2024 09:00:05 +0100,
Anshuman Khandual <anshuman.khandual@....com> wrote:
> 
> Currently read_sanitised_id_aa64dfr0_el1() caps the ID_AA64DFR0.DebugVer to
> ID_AA64DFR0_DebugVer_V8P8, resulting in FEAT_Debugv8p9 not being exposed to
> the guest. MDSELR_EL1 register access in the guest, is currently trapped by
> the existing configuration of the fine-grained traps.

Please add support for the HDFGxTR2_EL2 registers in the trap routing
arrays, add support for the corresponding FGUs in the corresponding
structure, and condition the UNDEF on the lack of *guest* support for
the feature.

In short, implement the architecture as described in the pseudocode,
and not a cheap shortcut.

Thanks,

	M.

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