From: Keith Busch <kbusch@kernel.org>
To: linux-nvme@lists.infradead.org, hch@lst.de, sagi@grimberg.me
Cc: Keith Busch <kbusch@kernel.org>
Subject: [PATCHv2] nvme-pci: remove volatile cqes
Date: Tue, 28 Apr 2020 07:21:56 -0700 [thread overview]
Message-ID: <20200428142156.2269926-1-kbusch@kernel.org> (raw)
The completion queue entry is not volatile once the phase is confirmed.
Remove the volatile keywords and check the phase using the appropriate
READ_ONCE() accessor, allowing the compiler to optimize the remaining
completion path.
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
v1->v2: Split long line into a more readable format (Christoph)
drivers/nvme/host/pci.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 8ebcf40f04fe..eef5d6ab7565 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -166,7 +166,7 @@ struct nvme_queue {
void *sq_cmds;
/* only used for poll queues: */
spinlock_t cq_poll_lock ____cacheline_aligned_in_smp;
- volatile struct nvme_completion *cqes;
+ struct nvme_completion *cqes;
dma_addr_t sq_dma_addr;
dma_addr_t cq_dma_addr;
u32 __iomem *q_db;
@@ -908,8 +908,9 @@ static void nvme_pci_complete_rq(struct request *req)
/* We read the CQE phase first to check if the rest of the entry is valid */
static inline bool nvme_cqe_pending(struct nvme_queue *nvmeq)
{
- return (le16_to_cpu(nvmeq->cqes[nvmeq->cq_head].status) & 1) ==
- nvmeq->cq_phase;
+ struct nvme_completion *hcqe = &nvmeq->cqes[nvmeq->cq_head];
+
+ return (le16_to_cpu(READ_ONCE(hcqe->status)) & 1) == nvmeq->cq_phase;
}
static inline void nvme_ring_cq_doorbell(struct nvme_queue *nvmeq)
@@ -930,7 +931,7 @@ static inline struct blk_mq_tags *nvme_queue_tagset(struct nvme_queue *nvmeq)
static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
{
- volatile struct nvme_completion *cqe = &nvmeq->cqes[idx];
+ struct nvme_completion *cqe = &nvmeq->cqes[idx];
struct request *req;
if (unlikely(cqe->command_id >= nvmeq->q_depth)) {
--
2.24.1
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next reply other threads:[~2020-04-28 14:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 14:21 Keith Busch [this message]
2020-04-29 0:07 ` [PATCHv2] nvme-pci: remove volatile cqes Sagi Grimberg
2020-05-01 12:46 ` Christoph Hellwig
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