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From: Leonardo Bras <leo.bras@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Leonardo Bras <leo.bras@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
	Joey Gouly <joey.gouly@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Shuah Khan <shuah@kernel.org>, Oliver Upton <oupton@kernel.org>,
	Fuad Tabba <fuad.tabba@linux.dev>,
	Peter Maydell <peter.maydell@linaro.org>,
	Wei-Lin Chang <weilin.chang@arm.com>,
	Yao Yuan <yaoyuan@linux.alibaba.com>,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-kselftest@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v20 03/14] KVM: arm64: Manage GCS access and registers for guests
Date: Wed,  2 Sep 2026 17:44:18 +0100	[thread overview]
Message-ID: <aphSYqKrgUq5Qycu@LeoBrasDK> (raw)
In-Reply-To: <20260901-arm64-gcs-v20-3-f31750bdfadb@kernel.org>

Hi Mark,

On Tue, Sep 01, 2026 at 10:47:01PM +0100, Mark Brown wrote:
> GCS introduces a number of system registers, on systems with GCS we need
> to context switch them and expose them to VMMs to allow guests to use
> GCS.
> 
> In order to allow guests to use GCS we also need to configure
> HCRX_EL2.GCSEn, if this is not set GCS instructions will be noops and
> CHKFEAT will report GCS as disabled.
> 

Everything you do seems the correct approach, and all the loads/saves 
are symmetrical, except for VEL2, for which the reason was made known 
in v19 discussion.

That being said, I may have missed something as I am still not very much 
used to NV code. So, FWIW:

Reviewed-by: Leonardo Bras <leo.bras@arm.com>

Nit:
Reading this patch, it feels like it should have been two different 
patches: one for adding the registers to kvm infra, and the other for 
loading/saving it in the code (with GCSEn). If you later decide to split 
it, feel free to add my R-b in both of them.

Thanks!
Leo




  parent reply	other threads:[~2026-09-02 16:44 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-01 21:46 [PATCH v20 00/14] KVM: arm64: Provide guest support for GCS Mark Brown
2026-09-01 21:46 ` [PATCH v20 01/14] arm64/gcs: Ensure FGTs for EL1 GCS instructions are disabled Mark Brown
2026-09-03 16:10   ` Lorenzo Stoakes (ARM)
2026-09-01 21:47 ` [PATCH v20 02/14] KVM: arm64: Fix FGT mapping for HFGITR_EL2.nGCSEPP Mark Brown
2026-09-03 16:23   ` Lorenzo Stoakes (ARM)
2026-09-03 19:29     ` Mark Brown
2026-09-15 22:25   ` (subset) " Oliver Upton
2026-09-01 21:47 ` [PATCH v20 03/14] KVM: arm64: Manage GCS access and registers for guests Mark Brown
2026-09-01 22:00   ` sashiko-bot
2026-09-02 16:44   ` Leonardo Bras [this message]
2026-09-03 20:52     ` Mark Brown
2026-09-03 18:13   ` Lorenzo Stoakes (ARM)
2026-09-03 20:41     ` Mark Brown
2026-09-04  8:54       ` Lorenzo Stoakes (ARM)
2026-09-04 21:07         ` Mark Brown
2026-09-07 14:14           ` Lorenzo Stoakes (ARM)
2026-09-07 14:55             ` Mark Brown
2026-09-09 11:34               ` Lorenzo Stoakes (ARM)
2026-09-01 21:47 ` [PATCH v20 04/14] KVM: arm64: Ensure GCS memory effects are visible Mark Brown
2026-09-01 22:06   ` sashiko-bot
2026-09-02 16:30   ` Leonardo Bras
2026-09-04 12:16   ` Lorenzo Stoakes (ARM)
2026-09-01 21:47 ` [PATCH v20 05/14] KVM: arm64: Set PSTATE.EXLOCK when entering an exception Mark Brown
2026-09-01 22:06   ` sashiko-bot
2026-09-03 14:25   ` Leonardo Bras
2026-09-03 16:20     ` Mark Brown
2026-09-03 16:40       ` Leonardo Bras
2026-09-04 13:04   ` Lorenzo Stoakes (ARM)
2026-09-01 21:47 ` [PATCH v20 06/14] KVM: arm64: Validate GCS exception lock when emulating ERET Mark Brown
2026-09-03 15:37   ` Leonardo Bras
2026-09-03 19:22     ` Mark Brown
2026-09-04 13:16       ` Leonardo Bras
2026-09-04 21:56         ` Mark Brown
2026-09-07 10:55           ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 07/14] KVM: arm64: Forward GCS exceptions to nested guests Mark Brown
2026-09-01 22:09   ` sashiko-bot
2026-09-09 13:00   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 08/14] KVM: arm64: Enforce EXLOCK for SPSR and ELR Mark Brown
2026-09-01 22:15   ` sashiko-bot
2026-09-01 22:48     ` Mark Brown
2026-09-09 14:35   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 09/14] KVM: arm64: Allow GCS to be enabled for guests Mark Brown
2026-09-09 16:34   ` Leonardo Bras
2026-09-09 16:45     ` Mark Brown
2026-09-01 21:47 ` [PATCH v20 10/14] KVM: selftests: arm64: Add GCS registers to get-reg-list Mark Brown
2026-09-01 22:05   ` sashiko-bot
2026-09-09 16:46   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 11/14] KVM: selftests: arm64: Add GCS to set_id_regs Mark Brown
2026-09-09 16:55   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 12/14] KVM: selftests: arm64: Only restore SPSR_EL1 and ELR_EL1 if they change Mark Brown
2026-09-09 17:03   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 13/14] tools: Synchronise the kernel esr.h Mark Brown
2026-09-01 22:08   ` sashiko-bot
2026-09-10 11:10   ` Leonardo Bras
2026-09-01 21:47 ` [PATCH v20 14/14] KVM: selftests: arm64: Add GCS EXLOCK exception emulation test Mark Brown
2026-09-01 22:16   ` sashiko-bot
2026-09-10 17:20   ` Leonardo Bras
2026-09-10 18:26     ` Mark Brown
2026-09-11 11:02       ` Leonardo Bras

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