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/**
 * @brief Provides access to MSR read & write operations
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef _WIN32
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#endif

#include "msr.h"

static int *m_msr_fd = NULL;           /**< MSR driver file descriptors table */
static unsigned m_maxcores = 0;        /**< max number of cores (size of the
                                          table above too) */

int
machine_init(const unsigned max_core_id)
{
#ifndef _WIN32
        unsigned i;

        if (max_core_id == 0)
                return MACHINE_RETVAL_PARAM;

        m_maxcores = max_core_id + 1;

        /**
         * Allocate table to hold MSR driver file descriptors
         * Each file descriptor is for a different core.
         * Core id is an index to the table.
         */
        m_msr_fd = (int *)malloc(m_maxcores * sizeof(m_msr_fd[0]));
        if (m_msr_fd == NULL) {
                m_maxcores = 0;
                return MACHINE_RETVAL_ERROR;
        }

        for (i = 0; i < m_maxcores; i++)
                m_msr_fd[i] = -1;
#endif /* _WIN32 */
        return MACHINE_RETVAL_OK;
}

int
machine_fini(void)
{
#ifndef _WIN32
        unsigned i;

        ASSERT(m_msr_fd != NULL);
        if (m_msr_fd == NULL)
                return MACHINE_RETVAL_ERROR;

        /**
         * Close open file descriptors and free up table memory.
         */
        for (i = 0; i < m_maxcores; i++)
                if (m_msr_fd[i] != -1) {
                        close(m_msr_fd[i]);
                        m_msr_fd[i] = -1;
                }

        free(m_msr_fd);
        m_msr_fd = NULL;
        m_maxcores = 0;
#endif /* _WIN32 */
        return MACHINE_RETVAL_OK;
}

#ifndef _WIN32
/**
 * @brief Returns MSR driver file descriptor for given core id
 *
 * File descriptor could be previously open and comes from
 * m_msr_fd table or is open (& cached) during the call.
 *
 * @param lcore logical core id
 *
 * @return MSR driver file descriptor corresponding \a lcore
 */
static int
msr_file_open(const unsigned lcore)
{
        ASSERT(lcore < m_maxcores);
        ASSERT(m_msr_fd != NULL);

        int fd = m_msr_fd[lcore];

        if (fd < 0) {
                char fname[32];

                memset(fname, 0, sizeof(fname));
                snprintf(fname, sizeof(fname)-1,
                         "/dev/cpu/%u/msr", lcore);
                fd = open(fname, O_RDWR);
                if (fd < 0)
                        fprintf(stderr, "Error opening file '%s'!\n", fname);
                else
                        m_msr_fd[lcore] = fd;
        }

        return fd;
}
#endif /* _WIN32 */

int
msr_read(const unsigned lcore,
         const uint32_t reg,
         uint64_t *value)
{
        int ret = MACHINE_RETVAL_OK;
#ifndef _WIN32
        int fd = -1;
        ssize_t read_ret = 0;

        ASSERT(value != NULL);
        if (value == NULL)
                return MACHINE_RETVAL_PARAM;

        ASSERT(lcore < m_maxcores);
        if (lcore >= m_maxcores)
                return MACHINE_RETVAL_PARAM;

        ASSERT(m_msr_fd != NULL);
        if (m_msr_fd == NULL)
                return MACHINE_RETVAL_ERROR;

        fd = msr_file_open(lcore);
        if (fd < 0)
                return MACHINE_RETVAL_ERROR;

        read_ret = pread(fd, value, sizeof(value[0]), (off_t)reg);

        if (read_ret != sizeof(value[0])) {
                fprintf(stderr, "RDMSR failed for reg[0x%x] on lcore %u\n",
                        (unsigned)reg, lcore);
                ret = MACHINE_RETVAL_ERROR;
        }
#endif /* _WIN32 */
        return ret;
}

int
msr_write(const unsigned lcore,
          const uint32_t reg,
          const uint64_t value)
{
        int ret = MACHINE_RETVAL_OK;
#ifndef _WIN32
        int fd = -1;
        ssize_t write_ret = 0;

        ASSERT(lcore < m_maxcores);
        if (lcore >= m_maxcores)
                return MACHINE_RETVAL_PARAM;

        ASSERT(m_msr_fd != NULL);
        if (m_msr_fd == NULL)
                return MACHINE_RETVAL_ERROR;

        fd = msr_file_open(lcore);
        if (fd < 0)
                return MACHINE_RETVAL_ERROR;

        write_ret = pwrite(fd, &value, sizeof(value), (off_t)reg);

        if (write_ret != sizeof(value)) {
                fprintf(stderr, "WRMSR failed for reg[0x%x] "
                        "<- value[0x%llx] on lcore %u\n",
                        (unsigned)reg, (unsigned long long)value, lcore);
                ret = MACHINE_RETVAL_ERROR;
        }
#endif /* _WIN32 */
        return ret;
}