[PATCH v11 05/16] eal: use umonitor umwait and tpause intrinsics

[Bruce Richardson]

On Fri, Aug 11, 2023 at 12:20:47PM -0700, Tyler Retzlaff wrote:
> Inline assembly is not supported for MSVC x64 instead use _umonitor,
> _umwait and _tpause intrinsics.
> 
> Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> Acked-by: Konstantin Ananyev <konstantin.v.ananyev at yandex.ru>
> ---
>  lib/eal/x86/rte_power_intrinsics.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/eal/x86/rte_power_intrinsics.c b/lib/eal/x86/rte_power_intrinsics.c
> index f749da9..4066d13 100644
> --- a/lib/eal/x86/rte_power_intrinsics.c
> +++ b/lib/eal/x86/rte_power_intrinsics.c
> @@ -109,9 +109,13 @@
>  	 */
>  
>  	/* set address for UMONITOR */
> +#if defined(RTE_TOOLCHAIN_MSVC) || defined(__WAITPKG__)
> +	_umonitor(pmc->addr);
> +#else

This change is unfortunately giving build errors on system with WAITPKG,
since the intrinsics do not take volatile parameters, unlike the inline ASM
which works fine with both volatile and non-volatile variables. This is the
error I see:

../lib/eal/x86/rte_power_intrinsics.c: In function 'rte_power_monitor':
../lib/eal/x86/rte_power_intrinsics.c:113:22: error: passing argument 1 of '_umonitor' discards 'volatile' qualifier from pointer target type [-Werror=discarded-qualifiers]
  113 |         _umonitor(pmc->addr);
      |                   ~~~^~~~~~

The easy fix for now seems to be just dropping the "||
defined(__WAITPKG__)" part of the #ifdef, and leave the intrinsic for MSVC
only.
Any objections?

/Bruce