Baptiste Le Duc 861e44a3ba xen/riscv: make Zihintpause no longer a required extension ...

Zihintpause is in required_extensions[] so Xen panics when it is missing,
while it does not strictly require hardware support for it.

The PAUSE hint (Zihintpause extension) is encoded as FENCE W, 0
(0x0100000F). In accordance with the RISC-V Unprivileged ISA, HINTs are
encoded in the space of valid standard instructions. On platforms without
Zihintpause support, executing 0x0100000F is treated as a standard FENCE
with an empty successor set, which acts as a NOP and never generates an
illegal instruction trap.

Zihintpause is therefore purely an optimization hint. Drop it from
required_extensions[] so Xen can still boot on systems that don't advertise
it, and print a warning in that case.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Baptiste Le Duc <baptiste.le-duc@vates.tech>
Reviewed-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

2026-09-30 15:00:48 +02:00

..

booting.txt

xen/riscv: make Zihintpause no longer a required extension

2026-09-30 15:00:48 +02:00