[v13,02/11] eal: avoid invalid API usage in power intrinsics

  Currently, the API documentation mandates that if the user wants to use
the power management intrinsics, they need to call the
`rte_cpu_get_intrinsics_support` API and check support for specific
intrinsics.

However, if the user does not do that, it is possible to get illegal
instruction error because we're using raw instruction opcodes, which may
or may not be supported at runtime.

Now that we have everything in a C file, we can check for support at
startup and prevent the user from possibly encountering illegal
instruction errors.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 .../include/generic/rte_power_intrinsics.h    |  3 --
 lib/librte_eal/x86/rte_power_intrinsics.c     | 31 +++++++++++++++++--
 2 files changed, 28 insertions(+), 6 deletions(-)
  

On Fri,  8 Jan 2021 17:42:05 +0000
Anatoly Burakov <anatoly.burakov@intel.com> wrote:

> +static uint8_t wait_supported;

Since it is being used as a flag, bool is more common usage.
  

On 08-Jan-21 7:58 PM, Stephen Hemminger wrote:
> On Fri,  8 Jan 2021 17:42:05 +0000
> Anatoly Burakov <anatoly.burakov@intel.com> wrote:
> 
>> +static uint8_t wait_supported;
> 
> Since it is being used as a flag, bool is more common usage.
> 

Will fix in v14, thanks!
  

> Currently, the API documentation mandates that if the user wants to use
> the power management intrinsics, they need to call the
> `rte_cpu_get_intrinsics_support` API and check support for specific
> intrinsics.
> 
> However, if the user does not do that, it is possible to get illegal
> instruction error because we're using raw instruction opcodes, which may
> or may not be supported at runtime.
> 
> Now that we have everything in a C file, we can check for support at
> startup and prevent the user from possibly encountering illegal
> instruction errors.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> ---
>  .../include/generic/rte_power_intrinsics.h    |  3 --
>  lib/librte_eal/x86/rte_power_intrinsics.c     | 31 +++++++++++++++++--
>  2 files changed, 28 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/librte_eal/include/generic/rte_power_intrinsics.h b/lib/librte_eal/include/generic/rte_power_intrinsics.h
> index 67977bd511..ffa72f7578 100644
> --- a/lib/librte_eal/include/generic/rte_power_intrinsics.h
> +++ b/lib/librte_eal/include/generic/rte_power_intrinsics.h
> @@ -34,7 +34,6 @@
>   *
>   * @warning It is responsibility of the user to check if this function is
>   *   supported at runtime using `rte_cpu_get_intrinsics_support()` API call.
> - *   Failing to do so may result in an illegal CPU instruction error.
>   *
>   * @param p
>   *   Address to monitor for changes.
> @@ -75,7 +74,6 @@ void rte_power_monitor(const volatile void *p,
>   *
>   * @warning It is responsibility of the user to check if this function is
>   *   supported at runtime using `rte_cpu_get_intrinsics_support()` API call.
> - *   Failing to do so may result in an illegal CPU instruction error.
>   *
>   * @param p
>   *   Address to monitor for changes.
> @@ -111,7 +109,6 @@ void rte_power_monitor_sync(const volatile void *p,
>   *
>   * @warning It is responsibility of the user to check if this function is
>   *   supported at runtime using `rte_cpu_get_intrinsics_support()` API call.
> - *   Failing to do so may result in an illegal CPU instruction error.
>   *
>   * @param tsc_timestamp
>   *   Maximum TSC timestamp to wait for. Note that the wait behavior is
> diff --git a/lib/librte_eal/x86/rte_power_intrinsics.c b/lib/librte_eal/x86/rte_power_intrinsics.c
> index 34c5fd9c3e..b48a54ec7f 100644
> --- a/lib/librte_eal/x86/rte_power_intrinsics.c
> +++ b/lib/librte_eal/x86/rte_power_intrinsics.c
> @@ -4,6 +4,8 @@
> 
>  #include "rte_power_intrinsics.h"
> 
> +static uint8_t wait_supported;
> +
>  static inline uint64_t
>  __get_umwait_val(const volatile void *p, const uint8_t sz)
>  {
> @@ -35,6 +37,11 @@ rte_power_monitor(const volatile void *p, const uint64_t expected_value,
>  {
>  	const uint32_t tsc_l = (uint32_t)tsc_timestamp;
>  	const uint32_t tsc_h = (uint32_t)(tsc_timestamp >> 32);
> +
> +	/* prevent user from running this instruction if it's not supported */
> +	if (!wait_supported)
> +		return;
> +
>  	/*
>  	 * we're using raw byte codes for now as only the newest compiler
>  	 * versions support this instruction natively.
> @@ -72,6 +79,11 @@ rte_power_monitor_sync(const volatile void *p, const uint64_t expected_value,
>  {
>  	const uint32_t tsc_l = (uint32_t)tsc_timestamp;
>  	const uint32_t tsc_h = (uint32_t)(tsc_timestamp >> 32);
> +
> +	/* prevent user from running this instruction if it's not supported */
> +	if (!wait_supported)
> +		return;
> +
>  	/*
>  	 * we're using raw byte codes for now as only the newest compiler
>  	 * versions support this instruction natively.
> @@ -112,9 +124,22 @@ rte_power_pause(const uint64_t tsc_timestamp)
>  	const uint32_t tsc_l = (uint32_t)tsc_timestamp;
>  	const uint32_t tsc_h = (uint32_t)(tsc_timestamp >> 32);
> 
> +	/* prevent user from running this instruction if it's not supported */
> +	if (!wait_supported)
> +		return;
> +
>  	/* execute TPAUSE */
>  	asm volatile(".byte 0x66, 0x0f, 0xae, 0xf7;"
> -			: /* ignore rflags */
> -			: "D"(0), /* enter C0.2 */
> -			"a"(tsc_l), "d"(tsc_h));
> +		: /* ignore rflags */
> +		: "D"(0), /* enter C0.2 */
> +		  "a"(tsc_l), "d"(tsc_h));
> +}
> +
> +RTE_INIT(rte_power_intrinsics_init) {
> +	struct rte_cpu_intrinsics i;
> +
> +	rte_cpu_get_intrinsics_support(&i);
> +
> +	if (i.power_monitor && i.power_pause)
> +		wait_supported = 1;
>  }
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

> 2.25.1