Re: [PATCH v3 4/4] hw/nvme: fix missing cq eventidx update

[Philippe Mathieu-Daudé]

On 12/12/22 12:32, Klaus Jensen wrote:
> From: Klaus Jensen <k.jensen@samsung.com>
>
> Prior to reading the shadow doorbell cq head, we have to update the
> eventidx. Otherwise, we risk that the driver will skip an mmio doorbell
> write. This happens on riscv64, as reported by Guenter.
>
> Adding the missing update to the cq eventidx fixes the issue.
>
> Fixes: 3f7fe8de3d49 ("hw/nvme: Implement shadow doorbell buffer support")
> Cc: qemu-stable@nongnu.org
> Cc: qemu-riscv@nongnu.org
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> ---
>   hw/nvme/ctrl.c | 17 +++++++++++++++--
>   1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index 8af70f0216f0..3df29ea68b2f 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -1334,10 +1334,22 @@ static inline void nvme_blk_write(BlockBackend *blk, 
> int64_t offset,
>       }
>   }


>   static void nvme_update_cq_head(NvmeCQueue *cq)
>   {
> -    pci_dma_read(PCI_DEVICE(cq->ctrl), cq->db_addr, &cq->head,
> -                 sizeof(cq->head));
> +    uint32_t v;
> +
> +    pci_dma_read(PCI_DEVICE(cq->ctrl), cq->db_addr, &v, sizeof(v));
> +
> +    cq->head = le32_to_cpu(v);
>   

Isn't this be part of the previous patch?

>       trace_pci_nvme_update_cq_head(cq->cqid, cq->head);
>   }