Re: [External] Re: [PATCH v7 06/12] util/dsa: Implement zero page checking in DSA task.

[Yichen Wang]

On Mon, Nov 25, 2024 at 7:53 AM Fabiano Rosas <farosas@suse.de> wrote:
>
> Yichen Wang <yichen.wang@bytedance.com> writes:
>
> > From: Hao Xiang <hao.xiang@linux.dev>
> >
> > Create DSA task with operation code DSA_OPCODE_COMPVAL.
> > Here we create two types of DSA tasks, a single DSA task and
> > a batch DSA task. Batch DSA task reduces task submission overhead
> > and hence should be the default option. However, due to the way DSA
> > hardware works, a DSA batch task must contain at least two individual
> > tasks. There are times we need to submit a single task and hence a
> > single DSA task submission is also required.
> >
> > 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 |  44 ++++++--
> >  util/dsa.c         | 254 +++++++++++++++++++++++++++++++++++++++++----
> >  2 files changed, 269 insertions(+), 29 deletions(-)
> >
> > diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> > index d24567f0be..cb407b8b49 100644
> > --- a/include/qemu/dsa.h
> > +++ b/include/qemu/dsa.h
> > @@ -16,6 +16,7 @@
> >  #define QEMU_DSA_H
> >
> >  #include "qapi/error.h"
> > +#include "exec/cpu-common.h"
> >  #include "qemu/thread.h"
> >  #include "qemu/queue.h"
> >
> > @@ -70,10 +71,11 @@ typedef struct QemuDsaBatchTask {
> >      QemuDsaTaskStatus status;
> >      int batch_size;
> >      bool *results;
> > +    /* Address of each pages in pages */
> > +    ram_addr_t *addr;
> >      QSIMPLEQ_ENTRY(QemuDsaBatchTask) entry;
> >  } QemuDsaBatchTask;
> >
> > -
> >  /**
> >   * @brief Initializes DSA devices.
> >   *
> > @@ -105,8 +107,26 @@ void qemu_dsa_cleanup(void);
> >   */
> >  bool qemu_dsa_is_running(void);
> >
> > +/**
> > + * @brief Initializes a buffer zero DSA batch task.
> > + *
> > + * @param batch_size The number of zero page checking tasks in the batch.
> > + * @return A pointer to the zero page checking tasks initialized.
> > + */
> > +QemuDsaBatchTask *
> > +buffer_zero_batch_task_init(int batch_size);
> > +
> > +/**
> > + * @brief Performs the proper cleanup on a DSA batch task.
> > + *
> > + * @param task A pointer to the batch task to cleanup.
> > + */
> > +void buffer_zero_batch_task_destroy(QemuDsaBatchTask *task);
> > +
> >  #else
> >
> > +typedef struct QemuDsaBatchTask {} QemuDsaBatchTask;
> > +
> >  static inline bool qemu_dsa_is_running(void)
> >  {
> >      return false;
> > @@ -114,19 +134,27 @@ static inline bool qemu_dsa_is_running(void)
> >
> >  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;
> > +    error_setg(errp, "DSA accelerator is not enabled.");
> > +    return -1;
>
> This should have been fixed in the patch that introduced this function.
>

Will be fixed directly in an earlier patch.

> >  }
> >
> >  static inline void qemu_dsa_start(void) {}
> >
> >  static inline void qemu_dsa_stop(void) {}
> >
> > -static inline void qemu_dsa_cleanup(void) {}
>
> Where did this go?
>

I will add it back in the next patch. Actually in the non-DSA patch,
this function is not being called. But I agree it should be back for
the sake of completeness.

> > +static inline QemuDsaBatchTask *buffer_zero_batch_task_init(int batch_size)
> > +{
> > +    return NULL;
> > +}
> > +
> > +static inline void buffer_zero_batch_task_destroy(QemuDsaBatchTask *task) 
> > {}
> > +
> > +static inline int
> > +buffer_is_zero_dsa_batch_sync(QemuDsaBatchTask *batch_task,
> > +                              const void **buf, size_t count, size_t len)
> > +{
> > +    return -1;
> > +}
> >
> >  #endif
> >
> > diff --git a/util/dsa.c b/util/dsa.c
> > index c3ca71df86..408c163195 100644
> > --- a/util/dsa.c
> > +++ b/util/dsa.c
> > @@ -48,6 +48,7 @@ uint32_t max_retry_count;
> >  static QemuDsaDeviceGroup dsa_group;
> >  static QemuDsaCompletionThread completion_thread;
> >
> > +static void buffer_zero_dsa_completion(void *context);
> >
> >  /**
> >   * @brief This function opens a DSA device's work queue and
> > @@ -174,7 +175,6 @@ dsa_device_group_start(QemuDsaDeviceGroup *group)
> >   *
> >   * @param group A pointer to the DSA device group.
> >   */
> > -__attribute__((unused))
> >  static void
> >  dsa_device_group_stop(QemuDsaDeviceGroup *group)
> >  {
> > @@ -210,7 +210,6 @@ dsa_device_group_cleanup(QemuDsaDeviceGroup *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)
> >  {
> > @@ -283,7 +282,6 @@ dsa_task_enqueue(QemuDsaDeviceGroup *group,
> >   * @param group A pointer to the DSA device group.
> >   * @return QemuDsaBatchTask* The DSA task being dequeued.
> >   */
> > -__attribute__((unused))
> >  static QemuDsaBatchTask *
> >  dsa_task_dequeue(QemuDsaDeviceGroup *group)
> >  {
> > @@ -338,22 +336,6 @@ submit_wi_int(void *wq, struct dsa_hw_desc *descriptor)
> >      return 0;
> >  }
> >
> > -/**
> > - * @brief Synchronously submits a DSA work item to the
> > - *        device work queue.
> > - *
> > - * @param wq A pointer to the DSA work queue's device memory.
> > - * @param descriptor A pointer to the DSA work item descriptor.
> > - *
> > - * @return int Zero if successful, non-zero otherwise.
> > - */
> > -__attribute__((unused))
> > -static int
> > -submit_wi(void *wq, struct dsa_hw_desc *descriptor)
> > -{
> > -    return submit_wi_int(wq, descriptor);
> > -}
> > -
>
> Why is this being removed?
>

This is the same as submit_wi_int(), so I feel like there is no need
for another wrapper.

> >  /**
> >   * @brief Asynchronously submits a DSA work item to the
> >   *        device work queue.
> > @@ -362,7 +344,6 @@ submit_wi(void *wq, struct dsa_hw_desc *descriptor)
> >   *
> >   * @return int Zero if successful, non-zero otherwise.
> >   */
> > -__attribute__((unused))
> >  static int
> >  submit_wi_async(QemuDsaBatchTask *task)
> >  {
> > @@ -391,7 +372,6 @@ submit_wi_async(QemuDsaBatchTask *task)
> >   *
> >   * @return int Zero if successful, non-zero otherwise.
> >   */
> > -__attribute__((unused))
> >  static int
> >  submit_batch_wi_async(QemuDsaBatchTask *batch_task)
> >  {
> > @@ -750,3 +730,235 @@ void qemu_dsa_cleanup(void)
> >      dsa_device_group_cleanup(&dsa_group);
> >  }
> >
> > +
> > +/* Buffer zero comparison DSA task implementations */
> > +/* =============================================== */
> > +
> > +/**
> > + * @brief Sets a buffer zero comparison DSA task.
> > + *
> > + * @param descriptor A pointer to the DSA task descriptor.
> > + * @param buf A pointer to the memory buffer.
> > + * @param len The length of the buffer.
> > + */
> > +static void
> > +buffer_zero_task_set_int(struct dsa_hw_desc *descriptor,
> > +                         const void *buf,
> > +                         size_t len)
> > +{
> > +    struct dsa_completion_record *completion =
> > +        (struct dsa_completion_record *)descriptor->completion_addr;
> > +
> > +    descriptor->xfer_size = len;
> > +    descriptor->src_addr = (uintptr_t)buf;
> > +    completion->status = 0;
> > +    completion->result = 0;
> > +}
> > +
> > +/**
> > + * @brief Resets a buffer zero comparison DSA batch task.
> > + *
> > + * @param task A pointer to the DSA batch task.
> > + */
> > +static void
> > +buffer_zero_task_reset(QemuDsaBatchTask *task)
> > +{
> > +    task->completions[0].status = DSA_COMP_NONE;
> > +    task->task_type = QEMU_DSA_TASK;
> > +    task->status = QEMU_DSA_TASK_READY;
> > +}
> > +
> > +/**
> > + * @brief Resets a buffer zero comparison DSA batch task.
> > + *
> > + * @param task A pointer to the batch task.
> > + * @param count The number of DSA tasks this batch task will contain.
> > + */
> > +static void
> > +buffer_zero_batch_task_reset(QemuDsaBatchTask *task, size_t count)
> > +{
> > +    task->batch_completion.status = DSA_COMP_NONE;
> > +    task->batch_descriptor.desc_count = count;
> > +    task->task_type = QEMU_DSA_BATCH_TASK;
> > +    task->status = QEMU_DSA_TASK_READY;
> > +}
> > +
> > +/**
> > + * @brief Sets a buffer zero comparison DSA task.
> > + *
> > + * @param task A pointer to the DSA task.
> > + * @param buf A pointer to the memory buffer.
> > + * @param len The buffer length.
> > + */
> > +static void
> > +buffer_zero_task_set(QemuDsaBatchTask *task,
> > +                     const void *buf,
> > +                     size_t len)
> > +{
> > +    buffer_zero_task_reset(task);
> > +    buffer_zero_task_set_int(&task->descriptors[0], buf, len);
> > +}
> > +
> > +/**
> > + * @brief Sets a buffer zero comparison batch task.
> > + *
> > + * @param batch_task A pointer to the batch task.
> > + * @param buf An array of memory buffers.
> > + * @param count The number of buffers in the array.
> > + * @param len The length of the buffers.
> > + */
> > +static void
> > +buffer_zero_batch_task_set(QemuDsaBatchTask *batch_task,
> > +                           const void **buf, size_t count, size_t len)
> > +{
> > +    assert(count > 0);
> > +    assert(count <= batch_task->batch_size);
> > +
> > +    buffer_zero_batch_task_reset(batch_task, count);
> > +    for (int i = 0; i < count; i++) {
> > +        buffer_zero_task_set_int(&batch_task->descriptors[i], buf[i], len);
> > +    }
> > +}
> > +
> > +/**
> > + * @brief Asychronously perform a buffer zero DSA operation.
> > + *
> > + * @param task A pointer to the batch task structure.
> > + * @param buf A pointer to the memory buffer.
> > + * @param len The length of the memory buffer.
> > + *
> > + * @return int Zero if successful, otherwise an appropriate error code.
> > + */
> > +__attribute__((unused))
> > +static int
> > +buffer_zero_dsa_async(QemuDsaBatchTask *task,
> > +                      const void *buf, size_t len)
> > +{
> > +    buffer_zero_task_set(task, buf, len);
> > +
> > +    return submit_wi_async(task);
> > +}
> > +
> > +/**
> > + * @brief Sends a memory comparison batch task to a DSA device and wait
> > + *        for completion.
> > + *
> > + * @param batch_task The batch task to be submitted to DSA device.
> > + * @param buf An array of memory buffers to check for zero.
> > + * @param count The number of buffers.
> > + * @param len The buffer length.
> > + */
> > +__attribute__((unused))
> > +static int
> > +buffer_zero_dsa_batch_async(QemuDsaBatchTask *batch_task,
> > +                            const void **buf, size_t count, size_t len)
> > +{
> > +    assert(count <= batch_task->batch_size);
> > +    buffer_zero_batch_task_set(batch_task, buf, count, len);
> > +
> > +    return submit_batch_wi_async(batch_task);
> > +}
> > +
> > +/**
> > + * @brief The completion callback function for buffer zero
> > + *        comparison DSA task completion.
> > + *
> > + * @param context A pointer to the callback context.
> > + */
> > +static void
> > +buffer_zero_dsa_completion(void *context)
> > +{
> > +    assert(context != NULL);
> > +
> > +    QemuDsaBatchTask *task = (QemuDsaBatchTask *)context;
> > +    qemu_sem_post(&task->sem_task_complete);
> > +}
> > +
> > +/**
> > + * @brief Wait for the asynchronous DSA task to complete.
> > + *
> > + * @param batch_task A pointer to the buffer zero comparison batch task.
> > + */
> > +__attribute__((unused))
> > +static void
> > +buffer_zero_dsa_wait(QemuDsaBatchTask *batch_task)
> > +{
> > +    qemu_sem_wait(&batch_task->sem_task_complete);
> > +}
> > +
> > +/**
> > + * @brief Initializes a buffer zero comparison DSA task.
> > + *
> > + * @param descriptor A pointer to the DSA task descriptor.
> > + * @param completion A pointer to the DSA task completion record.
> > + */
> > +static void
> > +buffer_zero_task_init_int(struct dsa_hw_desc *descriptor,
> > +                          struct dsa_completion_record *completion)
> > +{
> > +    descriptor->opcode = DSA_OPCODE_COMPVAL;
> > +    descriptor->flags = IDXD_OP_FLAG_RCR | IDXD_OP_FLAG_CRAV;
> > +    descriptor->comp_pattern = (uint64_t)0;
> > +    descriptor->completion_addr = (uint64_t)completion;
> > +}
> > +
> > +/**
> > + * @brief Initializes a buffer zero DSA batch task.
> > + *
> > + * @param batch_size The number of zero page checking tasks in the batch.
> > + * @return A pointer to the zero page checking tasks initialized.
> > + */
> > +QemuDsaBatchTask *
> > +buffer_zero_batch_task_init(int batch_size)
> > +{
> > +    QemuDsaBatchTask *task = qemu_memalign(64, sizeof(QemuDsaBatchTask));
> > +    int descriptors_size = sizeof(*task->descriptors) * batch_size;
> > +
> > +    memset(task, 0, sizeof(*task));
> > +    task->addr = g_new0(ram_addr_t, batch_size);
> > +    task->results = g_new0(bool, batch_size);
> > +    task->batch_size = batch_size;
> > +    task->descriptors =
> > +        (struct dsa_hw_desc *)qemu_memalign(64, descriptors_size);
> > +    memset(task->descriptors, 0, descriptors_size);
> > +    task->completions = (struct dsa_completion_record *)qemu_memalign(
> > +        32, sizeof(*task->completions) * batch_size);
> > +
> > +    task->batch_completion.status = DSA_COMP_NONE;
> > +    task->batch_descriptor.completion_addr = 
> > (uint64_t)&task->batch_completion;
> > +    /* TODO: Ensure that we never send a batch with count <= 1 */
> > +    task->batch_descriptor.desc_count = 0;
> > +    task->batch_descriptor.opcode = DSA_OPCODE_BATCH;
> > +    task->batch_descriptor.flags = IDXD_OP_FLAG_RCR | IDXD_OP_FLAG_CRAV;
> > +    task->batch_descriptor.desc_list_addr = (uintptr_t)task->descriptors;
> > +    task->status = QEMU_DSA_TASK_READY;
> > +    task->group = &dsa_group;
> > +    task->device = dsa_device_group_get_next_device(&dsa_group);
> > +
> > +    for (int i = 0; i < task->batch_size; i++) {
> > +        buffer_zero_task_init_int(&task->descriptors[i],
> > +                                  &task->completions[i]);
> > +    }
> > +
> > +    qemu_sem_init(&task->sem_task_complete, 0);
> > +    task->completion_callback = buffer_zero_dsa_completion;
> > +
> > +    return task;
> > +}
> > +
> > +/**
> > + * @brief Performs the proper cleanup on a DSA batch task.
> > + *
> > + * @param task A pointer to the batch task to cleanup.
> > + */
> > +void
> > +buffer_zero_batch_task_destroy(QemuDsaBatchTask *task)
> > +{
> > +    g_free(task->addr);
> > +    g_free(task->results);
> > +    qemu_vfree(task->descriptors);
> > +    qemu_vfree(task->completions);
> > +    task->results = NULL;
> > +    qemu_sem_destroy(&task->sem_task_complete);
> > +    qemu_vfree(task);
> > +}