Re: [PATCH] RISC-V: KVM: Add kvm-riscv.wfi_trap_policy to control VS-mode WFI trapping

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The use of `early_param` causes a build failure and breaks parameter configuration when KVM is compiled as a loadable module (`CONFIG_KVM=m`).
--

--- Patch [1]: [PATCH] RISC-V: KVM: Add kvm-riscv.wfi_trap_policy to control VS-mode WFI trapping ---
commit 6cc43e03229541ce24e1b37ff0f4554294688af7
Author: Yuhang.chen <yhchen312@gmail.com>

RISC-V: KVM: Add kvm-riscv.wfi_trap_policy to control VS-mode WFI trapping

This commit introduces a new parameter to control whether VS-mode WFI
instructions trap into KVM or execute natively.

> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index cf6e231e76e25..09afbb014b47d 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c

[ ... ]

> @@ -26,6 +27,42 @@
>  
>  static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_former_vcpu);
>  
> +/*
> + * WFI trap policy for VS-mode guests, controllable through the
> + * kvm-riscv.wfi_trap_policy= kernel command-line option.
> + */
> +enum kvm_riscv_wfi_trap_policy {
> +	KVM_RISCV_WFI_TRAP,	/* Default: trap VS-mode WFI into KVM */
> +	KVM_RISCV_WFI_NOTRAP,	/* Let VS-mode WFI execute natively */
> +};
> +
> +static enum kvm_riscv_wfi_trap_policy kvm_riscv_wfi_trap_policy __read_mostly =
> +	KVM_RISCV_WFI_TRAP;
> +
> +static int __init early_kvm_riscv_wfi_trap_policy_cfg(char *arg)
> +{
[ ... ]
> +	if (strcmp(arg, "notrap") == 0) {
> +		kvm_riscv_wfi_trap_policy = KVM_RISCV_WFI_NOTRAP;
> +		return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +early_param("kvm-riscv.wfi_trap_policy", early_kvm_riscv_wfi_trap_policy_cfg);

[Severity: Low]
Since KVM can be compiled as a loadable module (CONFIG_KVM=m), will this
use of early_param() cause a build failure?

In include/linux/init.h, early_param() is undefined when MODULE is defined.
Additionally, since early_param() only parses the early boot command line,
this setup prevents configuring the trap policy via arguments when KVM is
loaded dynamically.

Does this need to use module_param() or similar to ensure it builds correctly
as a module and accepts runtime arguments?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709115610.287420-1-yhchen312@gmail.com?part=1