Re: [RFC 5/8] KVM: arm64: Explicitly handle MDSELR_EL1 traps as UNDEFINED

From: Marc Zyngier <maz@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Jonathan Corbet <corbet@lwn.net>,
	Oliver Upton <oliver.upton@linux.dev>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Mark Brown <broonie@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [RFC 5/8] KVM: arm64: Explicitly handle MDSELR_EL1 traps as UNDEFINED
Date: Fri, 05 Apr 2024 11:15:37 +0100	[thread overview]
Message-ID: <86a5m8t8s6.wl-maz@kernel.org> (raw)
In-Reply-To: <20240405080008.1225223-6-anshuman.khandual@arm.com>

On Fri, 05 Apr 2024 09:00:05 +0100,
Anshuman Khandual <anshuman.khandual@arm.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.