From 31d1e340f0e8d53804d737571b2f2bb28a74ecc5 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Wed, 23 Apr 2008 11:55:45 -0700 Subject: [PATCH] RDMA/nes: Remove volatile qualifier from struct nes_hw_cq.cq_vbase Remove the volatile qualifier from the cq_vbase member of struct nes_hw_cq, and add an rmb() in the one place where it looks like access order might make a difference. As usual, removing a volatile qualifier in a declaration is actually a bug fix, since a volatile qualifier is not sufficient to make sure that aggressively out-of-order CPUs don't reorder things and cause incorrect results. For example, a CPU might speculatively execute reads of other cqe fields before the NIC hardware has written those fields and before it has set the NES_CQE_VALID bit (even though those reads come after the test of the NES_CQE_VALID bit in program order), but then when the CPU actually executes the conditional test of the NES_CQE_VALID, the bit has been set, and the CPU will proceed with the results of the earlier speculative execution and end up using bogus data. This also gets rid of the warning: drivers/infiniband/hw/nes/nes_verbs.c: In function 'nes_destroy_cq': drivers/infiniband/hw/nes/nes_verbs.c:1978: warning: passing argument 3 of 'pci_free_consistent' discards qualifiers from pointer target type Signed-off-by: Roland Dreier --- drivers/infiniband/hw/nes/nes_hw.h | 2 +- drivers/infiniband/hw/nes/nes_verbs.c | 8 +++++++- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/infiniband/hw/nes/nes_hw.h b/drivers/infiniband/hw/nes/nes_hw.h index b7e2844f096b..8f36e231bdf5 100644 --- a/drivers/infiniband/hw/nes/nes_hw.h +++ b/drivers/infiniband/hw/nes/nes_hw.h @@ -905,7 +905,7 @@ struct nes_hw_qp { }; struct nes_hw_cq { - struct nes_hw_cqe volatile *cq_vbase; /* PCI memory for host rings */ + struct nes_hw_cqe *cq_vbase; /* PCI memory for host rings */ void (*ce_handler)(struct nes_device *nesdev, struct nes_hw_cq *cq); dma_addr_t cq_pbase; /* PCI memory for host rings */ u16 cq_head; diff --git a/drivers/infiniband/hw/nes/nes_verbs.c b/drivers/infiniband/hw/nes/nes_verbs.c index f9a5d4390892..ee74f7c7a6da 100644 --- a/drivers/infiniband/hw/nes/nes_verbs.c +++ b/drivers/infiniband/hw/nes/nes_verbs.c @@ -1976,7 +1976,7 @@ static int nes_destroy_cq(struct ib_cq *ib_cq) if (nescq->cq_mem_size) pci_free_consistent(nesdev->pcidev, nescq->cq_mem_size, - (void *)nescq->hw_cq.cq_vbase, nescq->hw_cq.cq_pbase); + nescq->hw_cq.cq_vbase, nescq->hw_cq.cq_pbase); kfree(nescq); return ret; @@ -3610,6 +3610,12 @@ static int nes_poll_cq(struct ib_cq *ibcq, int num_entries, struct ib_wc *entry) while (cqe_count < num_entries) { if (le32_to_cpu(nescq->hw_cq.cq_vbase[head].cqe_words[NES_CQE_OPCODE_IDX]) & NES_CQE_VALID) { + /* + * Make sure we read CQ entry contents *after* + * we've checked the valid bit. + */ + rmb(); + cqe = nescq->hw_cq.cq_vbase[head]; nescq->hw_cq.cq_vbase[head].cqe_words[NES_CQE_OPCODE_IDX] = 0; u32temp = le32_to_cpu(cqe.cqe_words[NES_CQE_COMP_COMP_CTX_LOW_IDX]);