linux-kernel - Re: [PATCH v2 6/6] KVM: arm64: initialise SCTLR2_EL1 at __kvm_host_psci_cpu

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Message-ID: <86qzxh927n.wl-maz@kernel.org>
Date: Mon, 11 Aug 2025 18:51:08 +0100
From: Marc Zyngier <maz@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com,
	will@...nel.org,
	broonie@...nel.org,
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	linux-arm-kernel@...ts.infradead.org,
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	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v2 6/6] KVM: arm64: initialise SCTLR2_EL1 at __kvm_host_psci_cpu_entry()

On Mon, 11 Aug 2025 17:33:40 +0100,
Yeoreum Yun <yeoreum.yun@....com> wrote:
> 
> initialise SCTLR2_EL1 at __kvm_host_psci_cpu_entry().

Same comment, I don't think this is an acceptable commit message.
Please ask for help if you don't feel confident writing it (I'm sure
some of your colleagues will be happy to help).

> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> ---
>  arch/arm64/kvm/hyp/nvhe/psci-relay.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index c3e196fb8b18..4ed4b7fa57c2 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -4,6 +4,7 @@
>   * Author: David Brazdil <dbrazdil@...gle.com>
>   */
>  
> +#include <asm/alternative.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_hyp.h>
>  #include <asm/kvm_mmu.h>
> @@ -219,6 +220,8 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
>  		release_boot_args(boot_args);
>  
>  	write_sysreg_el1(INIT_SCTLR_EL1_MMU_OFF, SYS_SCTLR);
> +	if (alternative_has_cap_unlikely(ARM64_HAS_SCTLR2))
> +		write_sysreg_el1(INIT_SCTLR2_EL1, SYS_SCTLR2);
>  	write_sysreg(INIT_PSTATE_EL1, SPSR_EL2);
>  
>  	__host_enter(host_ctxt);

This needs to be folded into patch #1.

Otherwise, there is a window of patches where the kernel will not
survive CPU hotplug when booted in protected mode.

	M.

-- 
Without deviation from the norm, progress is not possible.