[dpdk-dev] [PATCH v2] Patch introducing API to read/write Intel Architecture Model Specific Registers (MSR)...

[Ananyev, Konstantin]

Hi Wojciech,
Couple of nits, see below.
Konstantin

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Wojciech Andralojc
> Sent: Wednesday, January 20, 2016 10:57 AM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH v2] Patch introducing API to read/write Intel Architecture Model Specific Registers (MSR)...
> 
> Patch rework based on feedback, only x86 specific functions left under lib/librte_eal/common/include/arch/x86/.
> 
> Signed-off-by: Wojciech Andralojc <wojciechx.andralojc at intel.com>
> ---
>  lib/librte_eal/common/include/arch/x86/rte_msr.h | 158 +++++++++++++++++++++++
>  1 file changed, 158 insertions(+)
>  create mode 100644 lib/librte_eal/common/include/arch/x86/rte_msr.h
> 
> diff --git a/lib/librte_eal/common/include/arch/x86/rte_msr.h b/lib/librte_eal/common/include/arch/x86/rte_msr.h
> new file mode 100644
> index 0000000..9d16633
> --- /dev/null
> +++ b/lib/librte_eal/common/include/arch/x86/rte_msr.h
> +
> +#ifndef _RTE_MSR_X86_64_H_
> +#define _RTE_MSR_X86_64_H_
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +#include <fcntl.h> //O_RDONLY
> +#include <unistd.h> //pread

Pls remove '//' comments here.

> +
> +#include <rte_debug.h>
> +#include <rte_log.h>
> +
> +#define CPU_MSR_PATH "/dev/cpu/%u/msr"
> +#define CPU_MSR_PATH_MAX_LEN 32
> +
> +/**
> + * This function should not be called directly.
> + * Function to open CPU's MSR file
> + */
> +static int
> +__msr_open_file(const unsigned lcore, int flags)
> +{
> +	char fname[CPU_MSR_PATH_MAX_LEN] = {0};

Why not just  use PATH_MAX here?

> +	int fd = -1;
> +
> +	snprintf(fname, sizeof(fname) - 1, CPU_MSR_PATH, lcore);
> +
> +	fd = open(fname, flags);
> +
> +	if (fd < 0)
> +		RTE_LOG(ERR, PQOS, "Error opening file '%s'!\n", fname);
> +
> +	return fd;
> +}
> +
> +/**
> + * Function to read CPU's MSR
> + *
> + * @param [in] lcore
> + *  CPU logical core id

Hmm, are you aware that DPDK lcore id != CPU lcore id?
Might be better to use 'cpuid' name here?
Just to avoid confusion.

> + *
> + * @param [in] reg
> + *  MSR reg to read
> + *
> + * @param [out] value
> + *  Read value of MSR reg
> + *
> + * @return
> + *  Operations status
> +*/
> +
> +static inline int
> +rte_msr_read(const unsigned lcore, const uint32_t reg, uint64_t *value)

I don't think there is a need to put rte_msr_read/rte_msr_write() 
Definition into a header file and make them static inline.
Just normal external function definition seems sufficient here.

> +{
> +	int fd = -1;
> +	int ret = -1;
> +
> +	RTE_VERIFY(value != NULL);

That's a a public API.
No need to coredump if one of the input parameters is invalid.

> +	if (value == NULL)
> +		return -1;


Might be better -EINVAL;

> +
> +	fd = __msr_open_file(lcore, O_RDONLY);
> +
> +	if (fd >= 0) {
> +		ssize_t read_ret = 0;
> +
> +		read_ret = pread(fd, value, sizeof(value[0]), (off_t)reg);
> +
> +		if (read_ret != sizeof(value[0])) {
> +			RTE_LOG(ERR, PQOS, "RDMSR failed for reg[0x%x] on lcore %u\n",
> +				(unsigned)reg, lcore);
> +		} else
> +			ret = 0;
> +
> +		close(fd);
> +	}
> +
> +	return ret;
> +}