[PATCH] riscv: KVM: Fix compilation when CONFIG_RISCV_ISA_V=n

[Charlie Jenkins]

On Tue, Oct 06, 2026 at 04:39:03PM -0700, Charlie Jenkins wrote:
> Fix the KVM code to use stubbed out versions of vector functions when
> vector is not enabled instead of failing to compile. An alternative
> approach would be to ifdef out the vector code but since a handful of
> the vector code already just uses stubbed functions to tell the compiler
> to drop the implementation, follow the same pattern.
> 
> Fixes: b5060a4aa33d ("RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector")
> Signed-off-by: Charlie Jenkins <thecharlesjenkins at gmail.com>

Should have looked at the lists first, this wa already sent
https://lore.kernel.org/all/20260922021823.44251-2-zhangzhanpeng.jasper@bytedance.com/.

> ---
> I was reviewing [1] and noticed that when I disabled FPU and tried to
> compile that vector got disabled and the kernel failed to compile.
> 
> [1] https://lore.kernel.org/all/20261006075303.205216-1-radim.krcmar@oss.qualcomm.com/
> ---
>  arch/riscv/include/asm/kvm_vcpu_vector.h | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/kvm_vcpu_vector.h b/arch/riscv/include/asm/kvm_vcpu_vector.h
> index 6371d5ea5392..1c9efc6048bb 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_vector.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_vector.h
> @@ -11,9 +11,9 @@
>  #define __KVM_VCPU_RISCV_VECTOR_H
>  
>  #include <linux/types.h>
> +#include <asm/vector.h>
>  
>  #ifdef CONFIG_RISCV_ISA_V
> -#include <asm/vector.h>
>  #include <asm/kvm_host.h>
>  
>  static __always_inline void __kvm_riscv_vector_save(struct kvm_cpu_context *context)
> @@ -55,6 +55,14 @@ static inline void kvm_riscv_v_exit(void)
>  
>  struct kvm_cpu_context;
>  
> +static __always_inline void __kvm_riscv_vector_save(struct kvm_cpu_context *context)
> +{
> +}
> +
> +static __always_inline void __kvm_riscv_vector_restore(struct kvm_cpu_context *context)
> +{
> +}
> +
>  static inline void kvm_riscv_vcpu_vector_reset(struct kvm_vcpu *vcpu)
>  {
>  }
> 
> ---
> base-commit: a90ee4305c4a5df72c11b31dacfdc76e00fcf78a
> change-id: 20261006-vector_off_fix-938d61b1f906
> 
> Best regards,
> --  
> - Charlie
>