From d783e0bd02e700e7a893ef4fa71c69438ac1c276 Mon Sep 17 00:00:00 2001 From: Marta Rybczynska Date: Tue, 22 Mar 2016 16:02:06 +0100 Subject: [PATCH] nvme: avoid cqe corruption when update at the same time as read Make sure the CQE phase (validity) is read before the rest of the structure. The phase bit is the highest address and the CQE read will happen on most platforms from lower to upper addresses and will be done by multiple non-atomic loads. If the structure is updated by PCI during the reads from the processor, the processor may get a corrupted copy. The addition of the new nvme_cqe_valid function that verifies the validity bit also allows refactoring of the other CQE read sequences. Signed-off-by: Marta Rybczynska Reviewed-by: Johannes Thumshirn Reviewed-by: Christoph Hellwig Reviewed-by: Keith Busch Signed-off-by: Jens Axboe --- drivers/nvme/host/pci.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index f8db70ae172d..24ccda303efb 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -723,6 +723,13 @@ static void nvme_complete_rq(struct request *req) blk_mq_end_request(req, error); } +/* We read the CQE phase first to check if the rest of the entry is valid */ +static inline bool nvme_cqe_valid(struct nvme_queue *nvmeq, u16 head, + u16 phase) +{ + return (le16_to_cpu(nvmeq->cqes[head].status) & 1) == phase; +} + static void __nvme_process_cq(struct nvme_queue *nvmeq, unsigned int *tag) { u16 head, phase; @@ -730,13 +737,10 @@ static void __nvme_process_cq(struct nvme_queue *nvmeq, unsigned int *tag) head = nvmeq->cq_head; phase = nvmeq->cq_phase; - for (;;) { + while (nvme_cqe_valid(nvmeq, head, phase)) { struct nvme_completion cqe = nvmeq->cqes[head]; - u16 status = le16_to_cpu(cqe.status); struct request *req; - if ((status & 1) != phase) - break; if (++head == nvmeq->q_depth) { head = 0; phase = !phase; @@ -767,7 +771,7 @@ static void __nvme_process_cq(struct nvme_queue *nvmeq, unsigned int *tag) req = blk_mq_tag_to_rq(*nvmeq->tags, cqe.command_id); if (req->cmd_type == REQ_TYPE_DRV_PRIV && req->special) memcpy(req->special, &cqe, sizeof(cqe)); - blk_mq_complete_request(req, status >> 1); + blk_mq_complete_request(req, le16_to_cpu(cqe.status) >> 1); } @@ -808,18 +812,16 @@ static irqreturn_t nvme_irq(int irq, void *data) static irqreturn_t nvme_irq_check(int irq, void *data) { struct nvme_queue *nvmeq = data; - struct nvme_completion cqe = nvmeq->cqes[nvmeq->cq_head]; - if ((le16_to_cpu(cqe.status) & 1) != nvmeq->cq_phase) - return IRQ_NONE; - return IRQ_WAKE_THREAD; + if (nvme_cqe_valid(nvmeq, nvmeq->cq_head, nvmeq->cq_phase)) + return IRQ_WAKE_THREAD; + return IRQ_NONE; } static int nvme_poll(struct blk_mq_hw_ctx *hctx, unsigned int tag) { struct nvme_queue *nvmeq = hctx->driver_data; - if ((le16_to_cpu(nvmeq->cqes[nvmeq->cq_head].status) & 1) == - nvmeq->cq_phase) { + if (nvme_cqe_valid(nvmeq, nvmeq->cq_head, nvmeq->cq_phase)) { spin_lock_irq(&nvmeq->q_lock); __nvme_process_cq(nvmeq, &tag); spin_unlock_irq(&nvmeq->q_lock);