Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion

[Klaus Jensen <its@irrelevant.dk>]

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On Jul 28 16:07, Jinhao Fan wrote:
> With the introduction of shadow doorbell and ioeventfd, we need to do
> frequent conversion between qid and its doorbell offset. The original
> hard-coded calculation is confusing and error-prone. Add several helper
> functions to do this task.
> 
> Signed-off-by: Jinhao Fan <fanjinhao21s@ict.ac.cn>
> ---
>  hw/nvme/ctrl.c | 61 ++++++++++++++++++++++++++++++++------------------
>  1 file changed, 39 insertions(+), 22 deletions(-)
> 
> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index 533ad14e7a..6116c0e660 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -487,6 +487,29 @@ static int nvme_check_cqid(NvmeCtrl *n, uint16_t cqid)
>  {
>      return cqid < n->conf_ioqpairs + 1 && n->cq[cqid] != NULL ? 0 : -1;
>  }
> +static inline bool nvme_db_offset_is_cq(NvmeCtrl *n, hwaddr offset)
> +{
> +    hwaddr stride = 4 << NVME_CAP_DSTRD(ldq_le_p(&n->bar.cap));
> +    return (offset / stride) & 1;
> +}

This can be changed morphed into `(offset >> (2 + dstrd)) & 1` if I am not
mistaken.


> +
> +static inline uint16_t nvme_db_offset_to_qid(NvmeCtrl *n, hwaddr offset)
> +{
> +    hwaddr stride = 4 << NVME_CAP_DSTRD(ldq_le_p(&n->bar.cap));
> +    return offset / (2 * stride);
> +}

Same, should be able to do `offset >> (2 * dstrd + 1)`, no?

> +
> +static inline hwaddr nvme_cqid_to_db_offset(NvmeCtrl *n, uint16_t cqid)
> +{
> +    hwaddr stride = 4 << NVME_CAP_DSTRD(ldq_le_p(&n->bar.cap));
> +    return stride * (cqid * 2 + 1);
> +}
> +
> +static inline hwaddr nvme_sqid_to_db_offset(NvmeCtrl *n, uint16_t sqid)
> +{
> +    hwaddr stride = 4 << NVME_CAP_DSTRD(ldq_le_p(&n->bar.cap));
> +    return stride * sqid * 2;
> +}
>  
>  static void nvme_inc_cq_tail(NvmeCQueue *cq)
>  {
> @@ -4256,7 +4279,7 @@ static void nvme_cq_notifier(EventNotifier *e)
>  static int nvme_init_cq_ioeventfd(NvmeCQueue *cq)
>  {
>      NvmeCtrl *n = cq->ctrl;
> -    uint16_t offset = (cq->cqid << 3) + (1 << 2);
> +    uint16_t offset = nvme_cqid_to_db_offset(n, cq->cqid);
>      int ret;
>  
>      ret = event_notifier_init(&cq->notifier, 0);
> @@ -4283,7 +4306,7 @@ static void nvme_sq_notifier(EventNotifier *e)
>  static int nvme_init_sq_ioeventfd(NvmeSQueue *sq)
>  {
>      NvmeCtrl *n = sq->ctrl;
> -    uint16_t offset = sq->sqid << 3;
> +    uint16_t offset = nvme_sqid_to_db_offset(n, sq->sqid);
>      int ret;
>  
>      ret = event_notifier_init(&sq->notifier, 0);
> @@ -4300,7 +4323,7 @@ static int nvme_init_sq_ioeventfd(NvmeSQueue *sq)
>  
>  static void nvme_free_sq(NvmeSQueue *sq, NvmeCtrl *n)
>  {
> -    uint16_t offset = sq->sqid << 3;
> +    uint16_t offset = nvme_sqid_to_db_offset(n, sq->sqid);
>  
>      n->sq[sq->sqid] = NULL;
>      timer_free(sq->timer);
> @@ -4379,8 +4402,8 @@ static void nvme_init_sq(NvmeSQueue *sq, NvmeCtrl *n, uint64_t dma_addr,
>      sq->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, nvme_process_sq, sq);
>  
>      if (n->dbbuf_enabled) {
> -        sq->db_addr = n->dbbuf_dbs + (sqid << 3);
> -        sq->ei_addr = n->dbbuf_eis + (sqid << 3);
> +        sq->db_addr = n->dbbuf_dbs + nvme_sqid_to_db_offset(n, sqid);
> +        sq->ei_addr = n->dbbuf_eis + nvme_sqid_to_db_offset(n, sqid);
>  
>          if (n->params.ioeventfd && sq->sqid != 0) {
>              if (!nvme_init_sq_ioeventfd(sq)) {
> @@ -4690,8 +4713,8 @@ static uint16_t nvme_get_log(NvmeCtrl *n, NvmeRequest *req)
>  
>  static void nvme_free_cq(NvmeCQueue *cq, NvmeCtrl *n)
>  {
> -    uint16_t offset = (cq->cqid << 3) + (1 << 2);
> -
> +    uint16_t offset = nvme_cqid_to_db_offset(n, cq->cqid);
> +    
>      n->cq[cq->cqid] = NULL;
>      timer_free(cq->timer);
>      if (cq->ioeventfd_enabled) {
> @@ -4755,8 +4778,8 @@ static void nvme_init_cq(NvmeCQueue *cq, NvmeCtrl *n, uint64_t dma_addr,
>      QTAILQ_INIT(&cq->req_list);
>      QTAILQ_INIT(&cq->sq_list);
>      if (n->dbbuf_enabled) {
> -        cq->db_addr = n->dbbuf_dbs + (cqid << 3) + (1 << 2);
> -        cq->ei_addr = n->dbbuf_eis + (cqid << 3) + (1 << 2);
> +        cq->db_addr = n->dbbuf_dbs + nvme_cqid_to_db_offset(n, cqid);
> +        cq->ei_addr = n->dbbuf_eis + nvme_cqid_to_db_offset(n, cqid);
>  
>          if (n->params.ioeventfd && cqid != 0) {
>              if (!nvme_init_cq_ioeventfd(cq)) {
> @@ -6128,13 +6151,8 @@ static uint16_t nvme_dbbuf_config(NvmeCtrl *n, const NvmeRequest *req)
>          NvmeCQueue *cq = n->cq[i];
>  
>          if (sq) {
> -            /*
> -             * CAP.DSTRD is 0, so offset of ith sq db_addr is (i<<3)
> -             * nvme_process_db() uses this hard-coded way to calculate
> -             * doorbell offsets. Be consistent with that here.
> -             */
> -            sq->db_addr = dbs_addr + (i << 3);
> -            sq->ei_addr = eis_addr + (i << 3);
> +            sq->db_addr = dbs_addr + nvme_sqid_to_db_offset(n, i);
> +            sq->ei_addr = eis_addr + nvme_sqid_to_db_offset(n, i);
>              pci_dma_write(&n->parent_obj, sq->db_addr, &sq->tail,
>                      sizeof(sq->tail));
>  
> @@ -6146,9 +6164,8 @@ static uint16_t nvme_dbbuf_config(NvmeCtrl *n, const NvmeRequest *req)
>          }
>  
>          if (cq) {
> -            /* CAP.DSTRD is 0, so offset of ith cq db_addr is (i<<3)+(1<<2) */
> -            cq->db_addr = dbs_addr + (i << 3) + (1 << 2);
> -            cq->ei_addr = eis_addr + (i << 3) + (1 << 2);
> +            cq->db_addr = dbs_addr + nvme_cqid_to_db_offset(n, i);
> +            cq->ei_addr = eis_addr + nvme_cqid_to_db_offset(n, i);
>              pci_dma_write(&n->parent_obj, cq->db_addr, &cq->head,
>                      sizeof(cq->head));
>  
> @@ -6843,14 +6860,14 @@ static void nvme_process_db(NvmeCtrl *n, hwaddr addr, int val)
>          return;
>      }
>  
> -    if (((addr - 0x1000) >> 2) & 1) {
> +    if (nvme_db_offset_is_cq(n, addr - 0x1000)) {
>          /* Completion queue doorbell write */
>  
>          uint16_t new_head = val & 0xffff;
>          int start_sqs;
>          NvmeCQueue *cq;
>  
> -        qid = (addr - (0x1000 + (1 << 2))) >> 3;
> +        qid = nvme_db_offset_to_qid(n, addr - 0x1000);
>          if (unlikely(nvme_check_cqid(n, qid))) {
>              NVME_GUEST_ERR(pci_nvme_ub_db_wr_invalid_cq,
>                             "completion queue doorbell write"
> @@ -6925,7 +6942,7 @@ static void nvme_process_db(NvmeCtrl *n, hwaddr addr, int val)
>          uint16_t new_tail = val & 0xffff;
>          NvmeSQueue *sq;
>  
> -        qid = (addr - 0x1000) >> 3;
> +        qid = nvme_db_offset_to_qid(n, addr - 0x1000);
>          if (unlikely(nvme_check_sqid(n, qid))) {
>              NVME_GUEST_ERR(pci_nvme_ub_db_wr_invalid_sq,
>                             "submission queue doorbell write"
> -- 
> 2.25.1
> 

-- 
One of us - No more doubt, silence or taboo about mental illness.

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