Re: [PATCH] RISC-V: KVM: Fix builds without CONFIG_RISCV_ISA_V

[Ze Huang]

On Thu Oct 22, 2026 at 1:31 AM CST, slack up wrote:
> From: Xiaochun Yu <yxcnew@xxxxxxxxxxx>
>
> Commit b5060a4aa33d ("RISC-V: KVM: fix vcpu vector context
> handling for kernel-mode vector") made the KVM vCPU load and put paths
> call get_cpu_vector_context() and put_cpu_vector_context()
> unconditionally.  It also added an unconditional call to
> __kvm_riscv_vector_restore() on the guest entry path.
>
> The no-op definitions of the first two helpers live in <asm/vector.h>,
> but <asm/kvm_vcpu_vector.h> includes that header only when
> CONFIG_RISCV_ISA_V is enabled.  The KVM header also does not provide a
> no-op __kvm_riscv_vector_restore() in its disabled branch.  As a result,
> a KVM build without CONFIG_RISCV_ISA_V fails with missing helper
> declarations.
>
> Include <asm/vector.h> unconditionally to reuse its existing no-op
> helpers, and provide the missing KVM restore stub when Vector support is
> disabled.  This does not change the Vector-enabled path.
>
> Fixes: b5060a4aa33d ("RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Xiaochun Yu <yxcnew@xxxxxxxxxxx>
> ---
> This single patch fixes a build regression when KVM is enabled without the
> RISC-V Vector extension.
>
> Tested on base a804c5742bff (Torvalds master):
>
> - CONFIG_RISCV_ISA_V=n, CONFIG_KVM=m: full Image modules build passed.
> - CONFIG_RISCV_ISA_V=y, CONFIG_KVM=m: vcpu.o and vcpu_vector.o rebuilt.

Tested-by: Ze Huang <ze.huang@xxxxxxxxxxxxxxxx>

Tested on commit a804c5742bff with gcc 16.2.1 and clang 23.1.3:

CONFIG_RISCV_ISA_V=n, CONFIG_KVM=m: full Image + modules build passes
(before the patch: 3 implicit-declaration errors with gcc, 5 with clang)

> ---
>  arch/riscv/include/asm/kvm_vcpu_vector.h | 6 +++++-
>  1 file changed, 5 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..ebc619ed67dd 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 +55,10 @@ static inline void kvm_riscv_v_exit(void)
>  
>  struct kvm_cpu_context;
>  
> +static 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: a804c5742bff224d4cb4d25dd383554d598be32b
> change-id: 20261021-ospp-c1-b4-submit-e22dc09faf5a
>
> Best regards,