Re: [PATCH v6 03/12] util/dsa: Implement DSA device start and stop logic.

[Fabiano Rosas <farosas@suse.de>]

Yichen Wang <yichen.wang@bytedance.com> writes:

> From: Hao Xiang <hao.xiang@linux.dev>
>
> * DSA device open and close.
> * DSA group contains multiple DSA devices.
> * DSA group configure/start/stop/clean.
>
> Signed-off-by: Hao Xiang <hao.xiang@linux.dev>
> Signed-off-by: Bryan Zhang <bryan.zhang@bytedance.com>
> Signed-off-by: Yichen Wang <yichen.wang@bytedance.com>
> ---
>  include/qemu/dsa.h | 103 +++++++++++++++++
>  util/dsa.c         | 282 +++++++++++++++++++++++++++++++++++++++++++++
>  util/meson.build   |   3 +
>  3 files changed, 388 insertions(+)
>  create mode 100644 include/qemu/dsa.h
>  create mode 100644 util/dsa.c
>
> diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> new file mode 100644
> index 0000000000..501bb8c70d
> --- /dev/null
> +++ b/include/qemu/dsa.h
> @@ -0,0 +1,103 @@
> +/*
> + * Interface for using Intel Data Streaming Accelerator to offload certain
> + * background operations.
> + *
> + * Copyright (C) Bytedance Ltd.
> + *
> + * Authors:
> + *  Hao Xiang <hao.xiang@bytedance.com>
> + *  Yichen Wang <yichen.wang@bytedance.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_DSA_H
> +#define QEMU_DSA_H
> +
> +#include "qemu/error-report.h"
> +#include "qemu/thread.h"
> +#include "qemu/queue.h"
> +
> +#ifdef CONFIG_DSA_OPT
> +
> +#pragma GCC push_options
> +#pragma GCC target("enqcmd")
> +
> +#include <linux/idxd.h>
> +#include "x86intrin.h"
> +
> +typedef struct {
> +    void *work_queue;
> +} QemuDsaDevice;
> +
> +typedef QSIMPLEQ_HEAD(QemuDsaTaskQueue, QemuDsaBatchTask) QemuDsaTaskQueue;
> +
> +typedef struct {
> +    QemuDsaDevice *dsa_devices;
> +    int num_dsa_devices;
> +    /* The index of the next DSA device to be used. */
> +    uint32_t device_allocator_index;
> +    bool running;
> +    QemuMutex task_queue_lock;
> +    QemuCond task_queue_cond;
> +    QemuDsaTaskQueue task_queue;
> +} QemuDsaDeviceGroup;
> +
> +/**
> + * @brief Initializes DSA devices.
> + *
> + * @param dsa_parameter A list of DSA device path from migration parameter.
> + *
> + * @return int Zero if successful, otherwise non zero.
> + */
> +int qemu_dsa_init(const strList *dsa_parameter, Error **errp);
> +
> +/**
> + * @brief Start logic to enable using DSA.
> + */
> +void qemu_dsa_start(void);
> +
> +/**
> + * @brief Stop the device group and the completion thread.
> + */
> +void qemu_dsa_stop(void);
> +
> +/**
> + * @brief Clean up system resources created for DSA offloading.
> + */
> +void qemu_dsa_cleanup(void);
> +
> +/**
> + * @brief Check if DSA is running.
> + *
> + * @return True if DSA is running, otherwise false.
> + */
> +bool qemu_dsa_is_running(void);
> +
> +#else
> +
> +static inline bool qemu_dsa_is_running(void)
> +{
> +    return false;
> +}
> +
> +static inline int qemu_dsa_init(const strList *dsa_parameter, Error **errp)
> +{
> +    if (dsa_parameter != NULL && strlen(dsa_parameter) != 0) {
> +        error_setg(errp, "DSA is not supported.");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +static inline void qemu_dsa_start(void) {}
> +
> +static inline void qemu_dsa_stop(void) {}
> +
> +static inline void qemu_dsa_cleanup(void) {}
> +
> +#endif
> +
> +#endif
> diff --git a/util/dsa.c b/util/dsa.c
> new file mode 100644
> index 0000000000..54d0e20c29
> --- /dev/null
> +++ b/util/dsa.c
> @@ -0,0 +1,282 @@
> +/*
> + * Use Intel Data Streaming Accelerator to offload certain background
> + * operations.
> + *
> + * Copyright (C) Bytedance Ltd.
> + *
> + * Authors:
> + *  Hao Xiang <hao.xiang@bytedance.com>
> + *  Bryan Zhang <bryan.zhang@bytedance.com>
> + *  Yichen Wang <yichen.wang@bytedance.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qemu/queue.h"
> +#include "qemu/memalign.h"
> +#include "qemu/lockable.h"
> +#include "qemu/cutils.h"
> +#include "qemu/dsa.h"
> +#include "qemu/bswap.h"
> +#include "qemu/error-report.h"
> +#include "qemu/rcu.h"
> +
> +#pragma GCC push_options
> +#pragma GCC target("enqcmd")
> +
> +#include <linux/idxd.h>
> +#include "x86intrin.h"
> +
> +#define DSA_WQ_PORTAL_SIZE 4096
> +#define MAX_DSA_DEVICES 16
> +
> +uint32_t max_retry_count;
> +static QemuDsaDeviceGroup dsa_group;
> +
> +
> +/**
> + * @brief This function opens a DSA device's work queue and
> + *        maps the DSA device memory into the current process.
> + *
> + * @param dsa_wq_path A pointer to the DSA device work queue's file path.
> + * @return A pointer to the mapped memory, or MAP_FAILED on failure.
> + */
> +static void *
> +map_dsa_device(const char *dsa_wq_path)
> +{
> +    void *dsa_device;
> +    int fd;
> +
> +    fd = open(dsa_wq_path, O_RDWR);
> +    if (fd < 0) {
> +        error_report("Open %s failed with errno = %d.",
> +                dsa_wq_path, errno);
> +        return MAP_FAILED;
> +    }
> +    dsa_device = mmap(NULL, DSA_WQ_PORTAL_SIZE, PROT_WRITE,
> +                      MAP_SHARED | MAP_POPULATE, fd, 0);
> +    close(fd);
> +    if (dsa_device == MAP_FAILED) {
> +        error_report("mmap failed with errno = %d.", errno);
> +        return MAP_FAILED;
> +    }
> +    return dsa_device;
> +}
> +
> +/**
> + * @brief Initializes a DSA device structure.
> + *
> + * @param instance A pointer to the DSA device.
> + * @param work_queue A pointer to the DSA work queue.
> + */
> +static void
> +dsa_device_init(QemuDsaDevice *instance,
> +                void *dsa_work_queue)
> +{
> +    instance->work_queue = dsa_work_queue;
> +}
> +
> +/**
> + * @brief Cleans up a DSA device structure.
> + *
> + * @param instance A pointer to the DSA device to cleanup.
> + */
> +static void
> +dsa_device_cleanup(QemuDsaDevice *instance)
> +{
> +    if (instance->work_queue != MAP_FAILED) {
> +        munmap(instance->work_queue, DSA_WQ_PORTAL_SIZE);
> +    }
> +}
> +
> +/**
> + * @brief Initializes a DSA device group.
> + *
> + * @param group A pointer to the DSA device group.
> + * @param dsa_parameter A list of DSA device path from are separated by space
> + * character migration parameter. Multiple DSA device path.
> + *
> + * @return Zero if successful, non-zero otherwise.
> + */
> +static int
> +dsa_device_group_init(QemuDsaDeviceGroup *group,
> +                      const strList *dsa_parameter,
> +                      Error **errp)
> +{
> +    if (dsa_parameter == NULL) {
> +        error_setg(errp, "dsa device path is not supplied.");
> +        return -1;
> +    }
> +
> +    int ret = 0;
> +    const char *dsa_path[MAX_DSA_DEVICES];
> +    int num_dsa_devices = 0;
> +
> +    while (dsa_parameter) {
> +        dsa_path[num_dsa_devices++] = dsa_parameter->value;
> +        if (num_dsa_devices == MAX_DSA_DEVICES) {
> +            break;
> +        }
> +        dsa_parameter = dsa_parameter->next;
> +    }
> +
> +    group->dsa_devices =
> +        g_new0(QemuDsaDevice, num_dsa_devices);
> +    group->num_dsa_devices = num_dsa_devices;
> +    group->device_allocator_index = 0;
> +
> +    group->running = false;
> +    qemu_mutex_init(&group->task_queue_lock);
> +    qemu_cond_init(&group->task_queue_cond);
> +    QSIMPLEQ_INIT(&group->task_queue);
> +
> +    void *dsa_wq = MAP_FAILED;
> +    for (int i = 0; i < num_dsa_devices; i++) {
> +        dsa_wq = map_dsa_device(dsa_path[i]);
> +        if (dsa_wq == MAP_FAILED) {
> +            error_setg(errp, "map_dsa_device failed MAP_FAILED.");
> +            ret = -1;
> +            goto exit;

This will leave subsequent dsa_devices uninitialized after
map_dsa_device fails for the i-th device, but the loop at
dsa_device_group_cleanup() still passes all of them into
dsa_device_cleanup(), so the check != MAP_FAILED there will be true.

> +        }
> +        dsa_device_init(&dsa_group.dsa_devices[i], dsa_wq);

I think you mean &group->dsa_devices[i] here.

> +    }
> +
> +exit:
> +    return ret;
> +}
> +
> +/**
> + * @brief Starts a DSA device group.
> + *
> + * @param group A pointer to the DSA device group.
> + */
> +static void
> +dsa_device_group_start(QemuDsaDeviceGroup *group)
> +{
> +    group->running = true;
> +}
> +
> +/**
> + * @brief Stops a DSA device group.
> + *
> + * @param group A pointer to the DSA device group.
> + */
> +__attribute__((unused))
> +static void
> +dsa_device_group_stop(QemuDsaDeviceGroup *group)
> +{
> +    group->running = false;
> +}
> +
> +/**
> + * @brief Cleans up a DSA device group.
> + *
> + * @param group A pointer to the DSA device group.
> + */
> +static void
> +dsa_device_group_cleanup(QemuDsaDeviceGroup *group)
> +{
> +    if (!group->dsa_devices) {
> +        return;
> +    }
> +    for (int i = 0; i < group->num_dsa_devices; i++) {
> +        dsa_device_cleanup(&group->dsa_devices[i]);
> +    }
> +    g_free(group->dsa_devices);
> +    group->dsa_devices = NULL;
> +
> +    qemu_mutex_destroy(&group->task_queue_lock);
> +    qemu_cond_destroy(&group->task_queue_cond);
> +}
> +
> +/**
> + * @brief Returns the next available DSA device in the group.
> + *
> + * @param group A pointer to the DSA device group.
> + *
> + * @return struct QemuDsaDevice* A pointer to the next available DSA device
> + *         in the group.
> + */
> +__attribute__((unused))
> +static QemuDsaDevice *
> +dsa_device_group_get_next_device(QemuDsaDeviceGroup *group)
> +{
> +    if (group->num_dsa_devices == 0) {
> +        return NULL;
> +    }
> +    uint32_t current = qatomic_fetch_inc(&group->device_allocator_index);
> +    current %= group->num_dsa_devices;
> +    return &group->dsa_devices[current];
> +}
> +
> +/**
> + * @brief Check if DSA is running.
> + *
> + * @return True if DSA is running, otherwise false.
> + */
> +bool qemu_dsa_is_running(void)
> +{
> +    return false;
> +}
> +
> +static void
> +dsa_globals_init(void)
> +{
> +    max_retry_count = UINT32_MAX;
> +}
> +
> +/**
> + * @brief Initializes DSA devices.
> + *
> + * @param dsa_parameter A list of DSA device path from migration parameter.
> + *
> + * @return int Zero if successful, otherwise non zero.
> + */
> +int qemu_dsa_init(const strList *dsa_parameter, Error **errp)
> +{
> +    dsa_globals_init();
> +
> +    return dsa_device_group_init(&dsa_group, dsa_parameter, errp);
> +}
> +
> +/**
> + * @brief Start logic to enable using DSA.
> + *
> + */
> +void qemu_dsa_start(void)
> +{
> +    if (dsa_group.num_dsa_devices == 0) {
> +        return;
> +    }
> +    if (dsa_group.running) {
> +        return;
> +    }
> +    dsa_device_group_start(&dsa_group);
> +}
> +
> +/**
> + * @brief Stop the device group and the completion thread.
> + *
> + */
> +void qemu_dsa_stop(void)
> +{
> +    QemuDsaDeviceGroup *group = &dsa_group;
> +
> +    if (!group->running) {
> +        return;
> +    }
> +}
> +
> +/**
> + * @brief Clean up system resources created for DSA offloading.
> + *
> + */
> +void qemu_dsa_cleanup(void)
> +{
> +    qemu_dsa_stop();
> +    dsa_device_group_cleanup(&dsa_group);
> +}
> +
> diff --git a/util/meson.build b/util/meson.build
> index 5d8bef9891..3360f62923 100644
> --- a/util/meson.build
> +++ b/util/meson.build
> @@ -88,6 +88,9 @@ if have_block or have_ga
>  endif
>  if have_block
>    util_ss.add(files('aio-wait.c'))
> +  if config_host_data.get('CONFIG_DSA_OPT')
> +    util_ss.add(files('dsa.c'))
> +  endif
>    util_ss.add(files('buffer.c'))
>    util_ss.add(files('bufferiszero.c'))
>    util_ss.add(files('hbitmap.c'))