Hao Xiang <hao.xi...@bytedance.com> writes:
> * Add a DSA task completion callback.
> * DSA completion thread will call the tasks's completion callback
> on every task/batch task completion.
> * DSA submission path to wait for completion.
> * Implement CPU fallback if DSA is not able to complete the task.
>
> Signed-off-by: Hao Xiang <hao.xi...@bytedance.com>
> Signed-off-by: Bryan Zhang <bryan.zh...@bytedance.com>
> ---
> include/qemu/dsa.h | 14 +++++
> util/dsa.c | 153 ++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 164 insertions(+), 3 deletions(-)
>
> diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> index b10e7b8fb7..3f8ee07004 100644
> --- a/include/qemu/dsa.h
> +++ b/include/qemu/dsa.h
> @@ -65,6 +65,20 @@ void buffer_zero_batch_task_init(struct
> buffer_zero_batch_task *task,
> */
> void buffer_zero_batch_task_destroy(struct buffer_zero_batch_task *task);
>
> +/**
> + * @brief Performs buffer zero comparison on a DSA batch task asynchronously.
> + *
> + * @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 buffer length.
> + *
> + * @return Zero if successful, otherwise non-zero.
> + */
> +int
> +buffer_is_zero_dsa_batch_async(struct buffer_zero_batch_task *batch_task,
> + const void **buf, size_t count, size_t len);
> +
> /**
> * @brief Initializes DSA devices.
> *
> diff --git a/util/dsa.c b/util/dsa.c
> index 3cc017b8a0..06c6fbf2ca 100644
> --- a/util/dsa.c
> +++ b/util/dsa.c
> @@ -470,6 +470,41 @@ poll_completion(struct dsa_completion_record *completion,
> return 0;
> }
>
> +/**
> + * @brief Use CPU to complete a single zero page checking task.
> + *
> + * @param task A pointer to the task.
> + */
> +static void
> +task_cpu_fallback(struct buffer_zero_batch_task *task)
> +{
> + assert(task->task_type == DSA_TASK);
> +
> + struct dsa_completion_record *completion = &task->completions[0];
> + const uint8_t *buf;
> + size_t len;
> +
> + if (completion->status == DSA_COMP_SUCCESS) {
> + return;
> + }
> +
> + /*
> + * DSA was able to partially complete the operation. Check the
> + * result. If we already know this is not a zero page, we can
> + * return now.
> + */
> + if (completion->bytes_completed != 0 && completion->result != 0) {
> + task->results[0] = false;
> + return;
> + }
> +
> + /* Let's fallback to use CPU to complete it. */
> + buf = (const uint8_t *)task->descriptors[0].src_addr;
> + len = task->descriptors[0].xfer_size;
> + task->results[0] = buffer_is_zero(buf + completion->bytes_completed,
> + len - completion->bytes_completed);
> +}
> +
> /**
> * @brief Complete a single DSA task in the batch task.
> *
> @@ -548,6 +583,62 @@ poll_batch_task_completion(struct buffer_zero_batch_task
> *batch_task)
> }
> }
>
> +/**
> + * @brief Use CPU to complete the zero page checking batch task.
> + *
> + * @param batch_task A pointer to the batch task.
> + */
> +static void
> +batch_task_cpu_fallback(struct buffer_zero_batch_task *batch_task)
> +{
> + assert(batch_task->task_type == DSA_BATCH_TASK);
> +
> + struct dsa_completion_record *batch_completion =
> + &batch_task->batch_completion;
> + struct dsa_completion_record *completion;
> + uint8_t status;
> + const uint8_t *buf;
> + size_t len;
> + bool *results = batch_task->results;
> + uint32_t count = batch_task->batch_descriptor.desc_count;
> +
> + // DSA is able to complete the entire batch task.
> + if (batch_completion->status == DSA_COMP_SUCCESS) {
> + assert(count == batch_completion->bytes_completed);
> + return;
> + }
> +
> + /*
> + * DSA encounters some error and is not able to complete
> + * the entire batch task. Use CPU fallback.
> + */
> + for (int i = 0; i < count; i++) {
> + completion = &batch_task->completions[i];
> + status = completion->status;
> + if (status == DSA_COMP_SUCCESS) {
> + continue;
> + }
> + assert(status == DSA_COMP_PAGE_FAULT_NOBOF);
> +
> + /*
> + * DSA was able to partially complete the operation. Check the
> + * result. If we already know this is not a zero page, we can
> + * return now.
> + */
> + if (completion->bytes_completed != 0 && completion->result != 0) {
> + results[i] = false;
> + continue;
> + }
> +
> + /* Let's fallback to use CPU to complete it. */
> + buf = (uint8_t *)batch_task->descriptors[i].src_addr;
> + len = batch_task->descriptors[i].xfer_size;
> + results[i] =
> + buffer_is_zero(buf + completion->bytes_completed,
> + len - completion->bytes_completed);
Here the same thing is happening as in other patches, the batch task
operation is just a repeat of the task operation n times. So this whole
inner code here could be nicely replaced by task_cpu_fallback() with
some adjustment of the function arguments. That makes intuitive sense
and removes code duplication.
> + }
> +}
> +
> /**
> * @brief Handles an asynchronous DSA batch task completion.
> *
> @@ -825,7 +916,6 @@ buffer_zero_batch_task_set(struct buffer_zero_batch_task
> *batch_task,
> *
> * @return int Zero if successful, otherwise an appropriate error code.
> */
> -__attribute__((unused))
> static int
> buffer_zero_dsa_async(struct buffer_zero_batch_task *task,
> const void *buf, size_t len)
> @@ -844,7 +934,6 @@ buffer_zero_dsa_async(struct buffer_zero_batch_task *task,
> * @param count The number of buffers.
> * @param len The buffer length.
> */
> -__attribute__((unused))
> static int
> buffer_zero_dsa_batch_async(struct buffer_zero_batch_task *batch_task,
> const void **buf, size_t count, size_t len)
> @@ -876,13 +965,29 @@ buffer_zero_dsa_completion(void *context)
> *
> * @param batch_task A pointer to the buffer zero comparison batch task.
> */
> -__attribute__((unused))
> static void
> buffer_zero_dsa_wait(struct buffer_zero_batch_task *batch_task)
> {
> qemu_sem_wait(&batch_task->sem_task_complete);
> }
>
> +/**
> + * @brief Use CPU to complete the zero page checking task if DSA
> + * is not able to complete it.
> + *
> + * @param batch_task A pointer to the batch task.
> + */
> +static void
> +buffer_zero_cpu_fallback(struct buffer_zero_batch_task *batch_task)
> +{
> + if (batch_task->task_type == DSA_TASK) {
> + task_cpu_fallback(batch_task);
> + } else {
> + assert(batch_task->task_type == DSA_BATCH_TASK);
> + batch_task_cpu_fallback(batch_task);
> + }
> +}
> +
> /**
> * @brief Check if DSA is running.
> *
> @@ -956,6 +1061,41 @@ void dsa_cleanup(void)
> dsa_device_group_cleanup(&dsa_group);
> }
>
> +/**
> + * @brief Performs buffer zero comparison on a DSA batch task asynchronously.
> + *
> + * @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 buffer length.
> + *
> + * @return Zero if successful, otherwise non-zero.
> + */
> +int
> +buffer_is_zero_dsa_batch_async(struct buffer_zero_batch_task *batch_task,
> + const void **buf, size_t count, size_t len)
> +{
> + if (count <= 0 || count > batch_task->batch_size) {
> + return -1;
> + }
> +
> + assert(batch_task != NULL);
> + assert(len != 0);
> + assert(buf != NULL);
> +
> + if (count == 1) {
> + // DSA doesn't take batch operation with only 1 task.
> + buffer_zero_dsa_async(batch_task, buf[0], len);
> + } else {
> + buffer_zero_dsa_batch_async(batch_task, buf, count, len);
> + }
> +
> + buffer_zero_dsa_wait(batch_task);
> + buffer_zero_cpu_fallback(batch_task);
> +
> + return 0;
> +}
> +
> #else
>
> void buffer_zero_batch_task_init(struct buffer_zero_batch_task *task,
> @@ -981,5 +1121,12 @@ void dsa_stop(void) {}
>
> void dsa_cleanup(void) {}
>
> +int
> +buffer_is_zero_dsa_batch_async(struct buffer_zero_batch_task *batch_task,
> + const void **buf, size_t count, size_t len)
> +{
> + exit(1);
> +}
> +
> #endif
