From: Marc Zyngier <maz@kernel.org>
To: Ard Biesheuvel <ardb@google.com>
Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
will@kernel.org, mark.rutland@arm.com,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH] arm64: Avoid enabling KPTI unnecessarily
Date: Mon, 27 Nov 2023 10:33:59 +0000 [thread overview]
Message-ID: <86h6l7cwo8.wl-maz@kernel.org> (raw)
In-Reply-To: <20231127102141.2241123-2-ardb@google.com>
On Mon, 27 Nov 2023 10:21:42 +0000,
Ard Biesheuvel <ardb@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Commit 42c5a3b04bf6 refactored the KPTI init code in a way that results
> in the use of non-global kernel mappings even on systems that have no
> need for it, and even when KPTI has been disabled explicitly via the
> command line.
>
> Ensure that this only happens when we have decided (based on the
> detected CPU features) that KPTI should be enabled.
>
> Fixes: 42c5a3b04bf6 ("arm64: Split kpti_install_ng_mappings()")
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/arm64/kernel/cpufeature.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 646591c67e7a..4b1762b9c37c 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -3352,7 +3352,8 @@ void __init setup_system_features(void)
> */
> enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);
>
> - kpti_install_ng_mappings();
> + if (arm64_kernel_unmapped_at_el0())
> + kpti_install_ng_mappings();
>
> sve_setup();
> sme_setup();
Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2023-11-27 10:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-27 10:21 [PATCH] arm64: Avoid enabling KPTI unnecessarily Ard Biesheuvel
2023-11-27 10:33 ` Marc Zyngier [this message]
2023-11-27 10:55 ` Ard Biesheuvel
2023-11-27 11:10 ` Mark Rutland
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