Yichen Wang <yichen.w...@bytedance.com> writes:
> From: Hao Xiang <hao.xi...@linux.dev>
>
> * 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...@linux.dev>
> Signed-off-by: Bryan Zhang <bryan.zh...@bytedance.com>
> Signed-off-by: Yichen Wang <yichen.w...@bytedance.com>
> ---
> include/qemu/dsa.h | 14 +++++
> util/dsa.c | 125 +++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 135 insertions(+), 4 deletions(-)
>
> diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> index cb407b8b49..8284804a32 100644
> --- a/include/qemu/dsa.h
> +++ b/include/qemu/dsa.h
> @@ -123,6 +123,20 @@ buffer_zero_batch_task_init(int batch_size);
> */
> void buffer_zero_batch_task_destroy(QemuDsaBatchTask *task);
>
> +/**
> + * @brief Performs buffer zero comparison on a DSA batch task synchronously.
> + *
> + * @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_sync(QemuDsaBatchTask *batch_task,
> + const void **buf, size_t count, size_t len);
> +
> #else
>
> typedef struct QemuDsaBatchTask {} QemuDsaBatchTask;
> diff --git a/util/dsa.c b/util/dsa.c
> index 408c163195..50f53ec24b 100644
> --- a/util/dsa.c
> +++ b/util/dsa.c
> @@ -433,6 +433,42 @@ poll_completion(struct dsa_completion_record *completion,
> return 0;
> }
>
> +/**
> + * @brief Helper function to use CPU to complete a single
> + * zero page checking task.
> + *
> + * @param completion A pointer to a DSA task completion record.
> + * @param descriptor A pointer to a DSA task descriptor.
> + * @param result A pointer to the result of a zero page checking.
> + */
> +static void
> +task_cpu_fallback_int(struct dsa_completion_record *completion,
> + struct dsa_hw_desc *descriptor, bool *result)
> +{
> + 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) {
> + *result = false;
> + return;
> + }
> +
> + /* Let's fallback to use CPU to complete it. */
> + buf = (const uint8_t *)descriptor->src_addr;
> + len = descriptor->xfer_size;
> + *result = buffer_is_zero(buf + completion->bytes_completed,
> + len - completion->bytes_completed);
> +}
> +
> /**
> * @brief Complete a single DSA task in the batch task.
> *
> @@ -561,7 +597,7 @@ dsa_completion_loop(void *opaque)
> (QemuDsaCompletionThread *)opaque;
> QemuDsaBatchTask *batch_task;
> QemuDsaDeviceGroup *group = thread_context->group;
> - int ret;
> + int ret = 0;
>
> rcu_register_thread();
>
> @@ -829,7 +865,6 @@ buffer_zero_batch_task_set(QemuDsaBatchTask *batch_task,
> *
> * @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)
> @@ -848,7 +883,6 @@ buffer_zero_dsa_async(QemuDsaBatchTask *task,
> * @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)
> @@ -879,13 +913,61 @@ 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(QemuDsaBatchTask *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(QemuDsaBatchTask *batch_task)
> +{
> + if (batch_task->task_type == QEMU_DSA_TASK) {
> + if (batch_task->completions[0].status == DSA_COMP_SUCCESS) {
> + return;
> + }
> + task_cpu_fallback_int(&batch_task->completions[0],
> + &batch_task->descriptors[0],
> + &batch_task->results[0]);
> + } else if (batch_task->task_type == QEMU_DSA_BATCH_TASK) {
> + struct dsa_completion_record *batch_completion =
> + &batch_task->batch_completion;
> + struct dsa_completion_record *completion;
> + uint8_t status;
> + 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;
> +
> + assert(status == DSA_COMP_SUCCESS ||
> + status == DSA_COMP_PAGE_FAULT_NOBOF);
> +
> + task_cpu_fallback_int(completion,
> + &batch_task->descriptors[i],
> + &results[i]);
> + }
> + }
> +}
> +
> /**
> * @brief Initializes a buffer zero comparison DSA task.
> *
> @@ -962,3 +1044,38 @@ buffer_zero_batch_task_destroy(QemuDsaBatchTask *task)
> qemu_sem_destroy(&task->sem_task_complete);
> qemu_vfree(task);
> }
> +
> +/**
> + * @brief Performs buffer zero comparison on a DSA batch task synchronously.
> + *
> + * @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_sync(QemuDsaBatchTask *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);
batch_task is already dereferenced above.
> + 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;
> +}
