[dpdk-dev] [PATCH v5 02/10] eal: add power management intrinsics

[David Christensen]

On 10/9/20 9:02 AM, Anatoly Burakov wrote:
> From: Liang Ma <liang.j.ma at intel.com>
> 
> Add two new power management intrinsics, and provide an implementation
> in eal/x86 based on UMONITOR/UMWAIT instructions. The instructions
> are implemented as raw byte opcodes because there is not yet widespread
> compiler support for these instructions.
> 
> The power management instructions provide an architecture-specific
> function to either wait until a specified TSC timestamp is reached, or
> optionally wait until either a TSC timestamp is reached or a memory
> location is written to. The monitor function also provides an optional
> comparison, to avoid sleeping when the expected write has already
> happened, and no more writes are expected.
> 
> For more details, please refer to Intel(R) 64 and IA-32 Architectures
> Software Developer's Manual, Volume 2.
> 
> Signed-off-by: Liang Ma <liang.j.ma at intel.com>
> Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
> ---
> 
> Notes:
>      v5:
>      - Removed return values
>      - Simplified intrinsics and hardcoded C0.2 state
>      - Added other arch stubs
> 

... snip ...

> +++ b/lib/librte_eal/ppc/include/rte_power_intrinsics.h
> @@ -0,0 +1,62 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2020 Intel Corporation
> + */
> +
> +#ifndef _RTE_POWER_INTRINSIC_PPC_H_
> +#define _RTE_POWER_INTRINSIC_PPC_H_
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +#include <rte_atomic.h>
> +#include <rte_common.h>
> +
> +#include "generic/rte_power_intrinsics.h"
> +
> +/**
> + * This function is not supported on PPC64.
> + *
> + * @param p
> + *   Address to monitor for changes. Must be aligned on an 64-byte boundary.
> + * @param expected_value
> + *   Before attempting the monitoring, the `p` address may be read and compared
> + *   against this value. If `value_mask` is zero, this step will be skipped.
> + * @param value_mask
> + *   The 64-bit mask to use to extract current value from `p`.
> + * @param tsc_timestamp
> + *   Maximum TSC timestamp to wait for.
> + *
> + * @return
> + *   - 0 on success
> + */
> +static inline void rte_power_monitor(const volatile void *p,
> +		const uint64_t expected_value, const uint64_t value_mask,
> +		const uint64_t tsc_timestamp)
> +{
> +	RTE_SET_USED(p);
> +	RTE_SET_USED(expected_value);
> +	RTE_SET_USED(value_mask);
> +	RTE_SET_USED(tsc_timestamp);
> +}
> +
> +/**
> + * This function is not supported on PPC64.
> + *
> + * @param tsc_timestamp
> + *   Maximum TSC timestamp to wait for.
> + *
> + * @return
> + *   - 1 if wakeup was due to TSC timeout expiration.
> + *   - 0 if wakeup was due to other reasons.
> + */
> +static inline void rte_power_pause(const uint64_t tsc_timestamp)
> +{
> +	RTE_SET_USED(tsc_timestamp);
> +}
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _RTE_POWER_INTRINSIC_PPC_H_ */

I didn't find an equivalent instruction in the current 3.1 ISA, so not 
supported is correct for POWER.

Acked-by: David Christensen <drc at linux.vnet.ibm.com>