Re: [PATCH v2 03/39] xen/riscv: set the guest's XLEN explicitly in hstatus.VSXL

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.08.2026 17:20, Oleksii Kurochko wrote:
> --- a/xen/arch/riscv/domain.c
> +++ b/xen/arch/riscv/domain.c
> @@ -88,7 +88,13 @@ static void vcpu_csr_init(struct vcpu *v)
>  {
>      v->arch.hedeleg = HEDELEG_DEFAULT & csr_masks.hedeleg;
>  
> -    vcpu_guest_cpu_user_regs(v)->hstatus = HSTATUS_SPV | HSTATUS_SPVP;
> +    /*
> +     * Xen supports 64-bit guests only, so set the guest's XLEN explicitly
> +     * rather than leaving it to the WARL behaviour of hstatus.VSXL, which 
> the
> +     * decoding of a trapped instruction depends on.
> +     */
> +    vcpu_guest_cpu_user_regs(v)->hstatus =
> +        HSTATUS_SPV | HSTATUS_SPVP | MASK_INSR(HSTATUS_VSXL_64, 
> HSTATUS_VSXL);

The comment is correct right now, but the situation better would change
at some point. Can't you arrange for things to be correct here also for
a future where 32- and 128-bit guests would also be supported?

> --- a/xen/arch/riscv/include/asm/riscv_encoding.h
> +++ b/xen/arch/riscv/include/asm/riscv_encoding.h
> @@ -68,6 +68,8 @@
>  #if __riscv_xlen == 64
>  #define HSTATUS_VSXL                 _UL(0x300000000)
>  #define HSTATUS_VSXL_SHIFT           32
> +#define HSTATUS_VSXL_64                      _UL(2)
> +#define HSTATUS_VSXL_32                      _UL(1)
>  #endif

While adding the two #define-s, would you mind considering to remove the
unused (and supposed to remain so) HSTATUS_VSXL_SHIFT?

Jan