[PATCH AUTOSEL 5.9 28/55] Revert "nvme-pci: remove last_sq_tail"

Sasha Levin
2020-11-10T04:05:38Z

From: Keith Busch <kbusch@kernel.org>

[ Upstream commit 38210800bf66d7302da1bb5b624ad68638da1562 ]

Multiple CPUs may be mapped to the same hctx, allowing mulitple
submission contexts to attempt commit_rqs(). We need to verify we're
not writing the same doorbell value multiple times since that's a spec
violation.

Revert commit 54b2fcee1db041a83b52b51752dade6090cf952f.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1878596
Reported-by: "B.L. Jones" <brandon.gustav@googlemail.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/nvme/host/pci.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 8984796db0c80..a6af96aaa0eb7 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -198,6 +198,7 @@ struct nvme_queue {
u32 q_depth;
u16 cq_vector;
u16 sq_tail;
+ u16 last_sq_tail;
u16 cq_head;
u16 qid;
u8 cq_phase;
@@ -455,11 +456,24 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)
return 0;
}

-static inline void nvme_write_sq_db(struct nvme_queue *nvmeq)
+/*
+ * Write sq tail if we are asked to, or if the next command would wrap.
+ */
+static inline void nvme_write_sq_db(struct nvme_queue *nvmeq, bool write_sq)
{
+ if (!write_sq) {
+ u16 next_tail = nvmeq->sq_tail + 1;
+
+ if (next_tail == nvmeq->q_depth)
+ next_tail = 0;
+ if (next_tail != nvmeq->last_sq_tail)
+ return;
+ }
+
if (nvme_dbbuf_update_and_check_event(nvmeq->sq_tail,
nvmeq->dbbuf_sq_db, nvmeq->dbbuf_sq_ei))
writel(nvmeq->sq_tail, nvmeq->q_db);
+ nvmeq->last_sq_tail = nvmeq->sq_tail;
}

/**
@@ -476,8 +490,7 @@ static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,
cmd, sizeof(*cmd));
if (++nvmeq->sq_tail == nvmeq->q_depth)
nvmeq->sq_tail = 0;
- if (write_sq)
- nvme_write_sq_db(nvmeq);
+ nvme_write_sq_db(nvmeq, write_sq);
spin_unlock(&nvmeq->sq_lock);
}

@@ -486,7 +499,8 @@ static void nvme_commit_rqs(struct blk_mq_hw_ctx *hctx)
struct nvme_queue *nvmeq = hctx->driver_data;

spin_lock(&nvmeq->sq_lock);
- nvme_write_sq_db(nvmeq);
+ if (nvmeq->sq_tail != nvmeq->last_sq_tail)
+ nvme_write_sq_db(nvmeq, true);
spin_unlock(&nvmeq->sq_lock);
}

@@ -1496,6 +1510,7 @@ static void nvme_init_queue(struct nvme_queue *nvmeq, u16 qid)
struct nvme_dev *dev = nvmeq->dev;

nvmeq->sq_tail = 0;
+ nvmeq->last_sq_tail = 0;
nvmeq->cq_head = 0;
nvmeq->cq_phase = 1;
nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];
--
2.27.0