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>, Fuad Tabba <tabba@google.com>,
Oliver Upton <oupton@kernel.org>,
Peter Maydell <peter.maydell@linaro.org>,
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 v19 01/14] arm64/gcs: Ensure FGTs for EL1 GCS instructions are disabled
Date: Wed, 19 Aug 2026 17:41:35 +0100 [thread overview]
Message-ID: <aoXcv8kx7x3GolaW@LeoBrasDK> (raw)
In-Reply-To: <a6fe8050-18f1-4013-8d6f-38ecc754c7e7@sirena.org.uk>
On Wed, Aug 19, 2026 at 03:21:31PM +0100, Mark Brown wrote:
> On Wed, Aug 19, 2026 at 02:41:13PM +0100, Leonardo Bras wrote:
> > On Wed, Aug 12, 2026 at 08:12:00PM +0100, Mark Brown wrote:
>
> > > + /* Disable traps of GCS instructions at EL1 */
> > > + orr x2, x2, #HFGITR_EL2_nGCSEPP_MASK
> > > + orr x2, x2, #HFGITR_EL2_nGCSSTR_EL1_MASK
> > > + orr x2, x2, #HFGITR_EL2_nGCSPUSHM_EL1_MASK
>
> > Which I understand to be the way of us saying that EL2 will not interfere
> > on nor manage those instructions that let software change the entries of
> > GCS. Is that correct?
>
> Yes, the goal is to allow EL1 to manage things how it wants (there are
> controls for store and push in GCSCR_EL1 too).
>
> > As for the asm routine, x2 at this point have nBRBIALL and nBRBINJ already
> > set, and will be loaded to SYS_HFGITR_EL2 in the next block of
> > instructions.
>
> > Did I get it right? Is there any missing detail here?
>
> That's the idea.
Awesome! FWIW:
Reviewed-by: Leonardo Bras <leo.bras@arm.com>
next prev parent reply other threads:[~2026-08-19 16:41 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-12 19:11 [PATCH v19 00/14] KVM: arm64: Provide guest support for GCS Mark Brown
2026-08-12 19:12 ` [PATCH v19 01/14] arm64/gcs: Ensure FGTs for EL1 GCS instructions are disabled Mark Brown
2026-08-19 13:41 ` Leonardo Bras
2026-08-19 14:21 ` Mark Brown
2026-08-19 16:41 ` Leonardo Bras [this message]
2026-08-12 19:12 ` [PATCH v19 02/14] KVM: arm64: Fix FGT mapping for HFGITR_EL2.nGCSEPP Mark Brown
2026-08-19 13:55 ` Leonardo Bras
2026-08-19 16:42 ` Leonardo Bras
2026-08-12 19:12 ` [PATCH v19 03/14] KVM: arm64: Manage GCS access and registers for guests Mark Brown
2026-08-19 16:32 ` Leonardo Bras
2026-08-19 16:46 ` Mark Brown
2026-08-12 19:12 ` [PATCH v19 04/14] KVM: arm64: Ensure GCS memory effects are visible Mark Brown
2026-08-19 17:23 ` Leonardo Bras
2026-08-19 18:08 ` Mark Brown
2026-08-12 19:12 ` [PATCH v19 05/14] KVM: arm64: Set PSTATE.EXLOCK when entering an exception Mark Brown
2026-08-12 19:12 ` [PATCH v19 06/14] KVM: arm64: Validate GCS exception lock when emulating ERET Mark Brown
2026-08-12 19:12 ` [PATCH v19 07/14] KVM: arm64: Forward GCS exceptions to nested guests Mark Brown
2026-08-12 19:12 ` [PATCH v19 08/14] KVM: arm64: Enforce EXLOCK for SPSR and ELR Mark Brown
2026-08-12 19:12 ` [PATCH v19 09/14] KVM: arm64: Allow GCS to be enabled for guests Mark Brown
2026-08-12 19:12 ` [PATCH v19 10/14] KVM: selftests: arm64: Add GCS registers to get-reg-list Mark Brown
2026-08-12 19:12 ` [PATCH v19 11/14] KVM: selftests: arm64: Add GCS to set_id_regs Mark Brown
2026-08-12 19:12 ` [PATCH v19 12/14] KVM: selftests: arm64: Only restore SPSR_EL1 and ELR_EL1 if they change Mark Brown
2026-08-12 19:12 ` [PATCH v19 13/14] tools: Synchronise the kernel esr.h Mark Brown
2026-08-12 19:12 ` [PATCH v19 14/14] KVM: selftests: arm64: Add GCS EXLOCK exception emulation test Mark Brown
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