Re: [PATCH v2 4/6] xen/riscv: make Zihintpause no longer a required extension

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 9/10/26 11:34 AM, Baptiste Le Duc wrote:
> required_extensions[] panics at boot if Zihintpause is missing, but Xen
> never actually depends on it: cpu_relax() only emits the "pause" hint when
> the extension is implemented, otherwise it emits `0x0100000F`, a legally
> valid FENCE instruction (`FENCE W, 0`) rather than a native NOP. FENCE is
> guaranteed by the RISC-V base ISA, so it never raises an illegal
> instruction fault. With an empty successor set, it enforces no
> memory-ordering constraints and thus architecturally behaves as a NOP.
>
> Drop it from required_extensions so hardware without Zihintpause
> still boots.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>
> ---
> Changes since v1:
> - rewrite commit message.
> ---
>   xen/arch/riscv/cpufeature.c | 1 -
>   1 file changed, 1 deletion(-)
Please update also booting.txt?

Thanks.

~ Oleksii