* [PATCH] hw/nvme: Add helper functions for qid-db conversion
@ 2022-07-28 8:07 Jinhao Fan
2022-08-02 3:46 ` Jinhao Fan
2022-08-02 6:02 ` Klaus Jensen
0 siblings, 2 replies; 8+ messages in thread
From: Jinhao Fan @ 2022-07-28 8:07 UTC (permalink / raw
To: qemu-devel; +Cc: its, kbusch, Jinhao Fan, open list:nvme
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;
+}
+
+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);
+}
+
+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
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-07-28 8:07 [PATCH] hw/nvme: Add helper functions for qid-db conversion Jinhao Fan
@ 2022-08-02 3:46 ` Jinhao Fan
2022-08-02 6:02 ` Klaus Jensen
1 sibling, 0 replies; 8+ messages in thread
From: Jinhao Fan @ 2022-08-02 3:46 UTC (permalink / raw
To: qemu-devel; +Cc: its, kbusch, open list:nvme
at 4:07 PM, Jinhao Fan <fanjinhao21s@ict.ac.cn> 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;
> +}
> +
> +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);
> +}
> +
> +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
Ping~
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-07-28 8:07 [PATCH] hw/nvme: Add helper functions for qid-db conversion Jinhao Fan
2022-08-02 3:46 ` Jinhao Fan
@ 2022-08-02 6:02 ` Klaus Jensen
2022-08-02 8:31 ` Jinhao Fan
1 sibling, 1 reply; 8+ messages in thread
From: Klaus Jensen @ 2022-08-02 6:02 UTC (permalink / raw
To: Jinhao Fan; +Cc: qemu-devel, kbusch, open list:nvme
[-- Attachment #1: Type: text/plain, Size: 6952 bytes --]
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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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-08-02 6:02 ` Klaus Jensen
@ 2022-08-02 8:31 ` Jinhao Fan
2022-08-02 8:54 ` Klaus Jensen
0 siblings, 1 reply; 8+ messages in thread
From: Jinhao Fan @ 2022-08-02 8:31 UTC (permalink / raw
To: Klaus Jensen; +Cc: qemu-devel, Keith Busch, open list:nvme
at 2:02 PM, Klaus Jensen <its@irrelevant.dk> wrote:
> 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.
>
Yes. But my current code looks more readable to me. Is it necessary to
change to `(offset >> (2 + dstrd)) & 1`.
>> +
>> +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?
Same as above.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-08-02 8:31 ` Jinhao Fan
@ 2022-08-02 8:54 ` Klaus Jensen
2022-08-02 10:05 ` Klaus Jensen
2022-08-03 1:46 ` Jinhao Fan
0 siblings, 2 replies; 8+ messages in thread
From: Klaus Jensen @ 2022-08-02 8:54 UTC (permalink / raw
To: Jinhao Fan; +Cc: qemu-devel, Keith Busch, open list:nvme
[-- Attachment #1: Type: text/plain, Size: 2101 bytes --]
On Aug 2 16:31, Jinhao Fan wrote:
> at 2:02 PM, Klaus Jensen <its@irrelevant.dk> wrote:
>
> > 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.
> >
>
> Yes. But my current code looks more readable to me. Is it necessary to
> change to `(offset >> (2 + dstrd)) & 1`.
>
I am unsure if the compiler will transform that division into the shift
if it can infer that the divisor is a power of two (it most likely
will be able to).
But I see no reason to have a potential division here when we can do
without and to me it is just as readable when you know the definition of
DSTRD is `2 ^ (2 + DSTRD)`.
> >> +
> >> +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?
>
> Same as above.
>
--
One of us - No more doubt, silence or taboo about mental illness.
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-08-02 8:54 ` Klaus Jensen
@ 2022-08-02 10:05 ` Klaus Jensen
2022-08-03 1:46 ` Jinhao Fan
1 sibling, 0 replies; 8+ messages in thread
From: Klaus Jensen @ 2022-08-02 10:05 UTC (permalink / raw
To: Jinhao Fan; +Cc: qemu-devel, Keith Busch, open list:nvme
[-- Attachment #1: Type: text/plain, Size: 2255 bytes --]
On Aug 2 10:54, Klaus Jensen wrote:
> On Aug 2 16:31, Jinhao Fan wrote:
> > at 2:02 PM, Klaus Jensen <its@irrelevant.dk> wrote:
> >
> > > 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.
> > >
> >
> > Yes. But my current code looks more readable to me. Is it necessary to
> > change to `(offset >> (2 + dstrd)) & 1`.
> >
>
> I am unsure if the compiler will transform that division into the shift
> if it can infer that the divisor is a power of two (it most likely
> will be able to).
>
> But I see no reason to have a potential division here when we can do
> without and to me it is just as readable when you know the definition of
> DSTRD is `2 ^ (2 + DSTRD)`.
>
> > >> +
> > >> +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?
> >
> > Same as above.
> >
>
I meant `offset >> (2 + dstrd + 1)` ('+', not '*') like above of course.
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-08-02 8:54 ` Klaus Jensen
2022-08-02 10:05 ` Klaus Jensen
@ 2022-08-03 1:46 ` Jinhao Fan
2022-08-03 2:36 ` Keith Busch
1 sibling, 1 reply; 8+ messages in thread
From: Jinhao Fan @ 2022-08-03 1:46 UTC (permalink / raw
To: Klaus Jensen; +Cc: qemu-devel, Keith Busch, open list:nvme
at 4:54 PM, Klaus Jensen <its@irrelevant.dk> wrote:
> I am unsure if the compiler will transform that division into the shift
> if it can infer that the divisor is a power of two (it most likely
> will be able to).
>
> But I see no reason to have a potential division here when we can do
> without and to me it is just as readable when you know the definition of
> DSTRD is `2 ^ (2 + DSTRD)`.
OK. I will send a new patch with shifts instead of divisions. BTW, why do we
want to avoid divisions?
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] hw/nvme: Add helper functions for qid-db conversion
2022-08-03 1:46 ` Jinhao Fan
@ 2022-08-03 2:36 ` Keith Busch
0 siblings, 0 replies; 8+ messages in thread
From: Keith Busch @ 2022-08-03 2:36 UTC (permalink / raw
To: Jinhao Fan; +Cc: Klaus Jensen, qemu-devel, open list:nvme
On Wed, Aug 03, 2022 at 09:46:05AM +0800, Jinhao Fan wrote:
> at 4:54 PM, Klaus Jensen <its@irrelevant.dk> wrote:
>
> > I am unsure if the compiler will transform that division into the shift
> > if it can infer that the divisor is a power of two (it most likely
> > will be able to).
> >
> > But I see no reason to have a potential division here when we can do
> > without and to me it is just as readable when you know the definition of
> > DSTRD is `2 ^ (2 + DSTRD)`.
>
> OK. I will send a new patch with shifts instead of divisions. BTW, why do we
> want to avoid divisions?
Integer division is at least an order of magnitude more CPU cycles than a
shift. Some archs are worse than others, but historically we go out of the way
to avoid them in a hot path, so shifting is a more familiar coding pattern.
Compilers typically implement division as a shift if you're dividing by a a
power of two integer constant expression (ICE).
This example here isn't an ICE, but it is a shifted constant power-of-two. I
wrote up a simple test to see what my compiler does with that, and it looks
like gcc will properly optimize it, but only if compiled with '-O3'.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-08-03 2:37 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-07-28 8:07 [PATCH] hw/nvme: Add helper functions for qid-db conversion Jinhao Fan
2022-08-02 3:46 ` Jinhao Fan
2022-08-02 6:02 ` Klaus Jensen
2022-08-02 8:31 ` Jinhao Fan
2022-08-02 8:54 ` Klaus Jensen
2022-08-02 10:05 ` Klaus Jensen
2022-08-03 1:46 ` Jinhao Fan
2022-08-03 2:36 ` Keith Busch
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