On Mon, Apr 14, 2025 at 01:11:44PM +0200, Peter Zijlstra wrote:
> +u64 hv_pg_hypercall(u64 control, u64 param1, u64 param2)
> +{
> + u64 hv_status;
> +
> + if (!hv_hypercall_pg)
> + return U64_MAX;
> +
> + register u64 __r8 asm("r8") = param2;
> + asm volatile (CALL_NOSPEC
> + : "=a" (hv_status), ASM_CALL_CONSTRAINT,
> + "+c" (control), "+d" (param1)
> + : "r" (__r8),
> + THUNK_TARGET(hv_hypercall_pg)
> + : "cc", "memory", "r9", "r10", "r11");
> +
> + return hv_status;
> +}
I've tried making this a tail-call, but even without the
ASM_CALL_CONSTRAINT on it confuses the compiler (objtool warns on
frame-pointer builds about non-matching stack).
I could of course have written the entire thing in asm, but meh.
