Re: [PATCH v2 4/5] hw/nvme: fix mmio read

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 7/13/21 9:24 PM, Klaus Jensen wrote:
> From: Klaus Jensen <k.jensen@samsung.com>
> 
> The new PMR test unearthed a long-standing issue with MMIO reads on
> big-endian hosts.
> 
> Fix this by unconditionally storing all controller registers in little
> endian.
> 
> Cc: Gollu Appalanaidu <anaidu.gollu@samsung.com>
> Reported-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> ---
>  hw/nvme/ctrl.c | 304 ++++++++++++++++++++++++++++---------------------
>  1 file changed, 174 insertions(+), 130 deletions(-)
> 
> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index 0449cc4dee9b..ddac9344a74e 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -439,10 +439,12 @@ static uint8_t nvme_sq_empty(NvmeSQueue *sq)
>  
>  static void nvme_irq_check(NvmeCtrl *n)
>  {
> +    uint32_t intms = le32_to_cpu(n->bar.intms);
> +
>      if (msix_enabled(&(n->parent_obj))) {
>          return;
>      }
> -    if (~n->bar.intms & n->irq_status) {
> +    if (~intms & n->irq_status) {
>          pci_irq_assert(&n->parent_obj);
>      } else {
>          pci_irq_deassert(&n->parent_obj);
> @@ -1289,7 +1291,7 @@ static void nvme_post_cqes(void *opaque)
>          if (ret) {
>              trace_pci_nvme_err_addr_write(addr);
>              trace_pci_nvme_err_cfs();
> -            n->bar.csts = NVME_CSTS_FAILED;
> +            n->bar.csts = cpu_to_le64(NVME_CSTS_FAILED);

The load/store API is safer than the cpu_to_X() one because
it removes alignment problems. Here it becomes:

               stq_le_p(&n->bar.csts, NVME_CSTS_FAILED);

>              break;
>          }
>          QTAILQ_REMOVE(&cq->req_list, req, entry);
> @@ -4022,7 +4024,7 @@ static uint16_t nvme_create_sq(NvmeCtrl *n, NvmeRequest *req)
>          trace_pci_nvme_err_invalid_create_sq_sqid(sqid);
>          return NVME_INVALID_QID | NVME_DNR;
>      }
> -    if (unlikely(!qsize || qsize > NVME_CAP_MQES(n->bar.cap))) {
> +    if (unlikely(!qsize || qsize > NVME_CAP_MQES(le64_to_cpu(n->bar.cap)))) {

And here:

 if (unlikely(!qsize || qsize > NVME_CAP_MQES(ldq_le_p(&n->bar.cap)))) {

>          trace_pci_nvme_err_invalid_create_sq_size(qsize);
>          return NVME_MAX_QSIZE_EXCEEDED | NVME_DNR;
>      }

However for the BAR is likely aligned, so using the cpu_to() API
shouldn't be a problem until we try to deprecate/remove it.