From: Marc Zyngier <maz@kernel•org>
To: Yeoreum Yun <yeoreum.yun@arm•com>
Cc: linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, kvmarm@lists•linux.dev,
kvm@vger•kernel.org, linux-kselftest@vger•kernel.org,
catalin.marinas@arm•com, will@kernel•org, oupton@kernel•org,
miko.lenczewski@arm•com, kevin.brodsky@arm•com,
broonie@kernel•org, ardb@kernel•org, suzuki.poulose@arm•com,
lpieralisi@kernel•org, joey.gouly@arm•com, yuzenghui@huawei•com
Subject: Re: [PATCH v17 7/8] KVM: arm64: use CAST instruction for swapping guest descriptor
Date: Tue, 17 Mar 2026 11:04:23 +0000 [thread overview]
Message-ID: <86o6km67k8.wl-maz@kernel.org> (raw)
In-Reply-To: <20260314175133.1084528-8-yeoreum.yun@arm.com>
On Sat, 14 Mar 2026 17:51:32 +0000,
Yeoreum Yun <yeoreum.yun@arm•com> wrote:
>
> Use the CAST instruction to swap the guest descriptor when FEAT_LSUI
> is enabled, avoiding the need to clear the PAN bit.
>
> FEAT_LSUI is introduced in Armv9.6, where FEAT_PAN is mandatory. However,
> this assumption may not always hold:
>
> - Some CPUs may advertise FEAT_LSUI but lack FEAT_PAN.
> - Virtualization or ID register overrides may expose invalid feature
> combinations.
>
> Therefore, instead of disabling FEAT_LSUI when FEAT_PAN is absent, wrap
> LSUI instructions with uaccess_ttbr0_enable()/disable() when
> ARM64_SW_TTBR0_PAN is enabled.
>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm•com>
Reviewed-by: Marc Zyngier <maz@kernel•org>
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2026-03-17 11:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-14 17:51 [PATCH v17 0/8] support FEAT_LSUI Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 1/8] arm64: cpufeature: add FEAT_LSUI Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 2/8] KVM: arm64: expose FEAT_LSUI to guest Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 3/8] KVM: arm64: kselftest: set_id_regs: add test for FEAT_LSUI Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 4/8] arm64: futex: refactor futex atomic operation Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 5/8] arm64: futex: support futex with FEAT_LSUI Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 6/8] arm64: armv8_deprecated: disable swp emulation when FEAT_LSUI present Yeoreum Yun
2026-03-14 17:51 ` [PATCH v17 7/8] KVM: arm64: use CAST instruction for swapping guest descriptor Yeoreum Yun
2026-03-17 11:04 ` Marc Zyngier [this message]
2026-03-14 17:51 ` [PATCH v17 8/8] arm64: Kconfig: add support for LSUI Yeoreum Yun
2026-03-27 13:16 ` (subset) [PATCH v17 0/8] support FEAT_LSUI Catalin Marinas
2026-03-27 13:56 ` Yeoreum Yun
2026-03-27 17:18 ` Catalin Marinas
2026-03-27 19:21 ` Catalin Marinas
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