Re: [PATCH v3 1/5] hw/nvme: split pmrmsc register into upper and lower

[Peter Maydell]

On Wed, 14 Jul 2021 at 07:01, Klaus Jensen <its@irrelevant.dk> wrote:
>
> From: Klaus Jensen <k.jensen@samsung.com>
>
> The specification uses a set of 32 bit PMRMSCL and PMRMSCU registers to
> make up the 64 bit logical PMRMSC register.
>
> Make it so.
>
> Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> ---
>  include/block/nvme.h | 31 ++++++++++++++++---------------
>  hw/nvme/ctrl.c       |  9 +++++----
>  2 files changed, 21 insertions(+), 19 deletions(-)

> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index 2f0524e12a36..28299c6f3764 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -5916,11 +5916,12 @@ static void nvme_write_bar(NvmeCtrl *n, hwaddr 
> offset, uint64_t data,
>              return;
>          }
>
> -        n->bar.pmrmsc = (n->bar.pmrmsc & ~0xffffffff) | (data & 0xffffffff);
> +        n->bar.pmrmscl = data & 0xffffffff;
>          n->pmr.cmse = false;
>
> -        if (NVME_PMRMSC_CMSE(n->bar.pmrmsc)) {
> -            hwaddr cba = NVME_PMRMSC_CBA(n->bar.pmrmsc) << PMRMSC_CBA_SHIFT;
> +        if (NVME_PMRMSCL_CMSE(n->bar.pmrmscl)) {
> +            hwaddr cba = n->bar.pmrmscu |
> +                (NVME_PMRMSCL_CBA(n->bar.pmrmscl) << PMRMSCL_CBA_SHIFT);

Don't we need to shift n->bar.pmrmscu left by 32 before we OR it in
with the pmrmscl part?

>              if (cba + int128_get64(n->pmr.dev->mr.size) < cba) {
>                  NVME_PMRSTS_SET_CBAI(n->bar.pmrsts, 1);
>                  return;
> @@ -5936,7 +5937,7 @@ static void nvme_write_bar(NvmeCtrl *n, hwaddr offset, 
> uint64_t data,
>              return;
>          }
>
> -        n->bar.pmrmsc = (n->bar.pmrmsc & 0xffffffff) | (data << 32);
> +        n->bar.pmrmscu = data & 0xffffffff;
>          return;

Not an issue with this patch, but why don't we need to do the
"update cba" stuff for a write to the U register that we do for
a write to the L register? Does the spec mandate that guests
do the writes in the order H then L and only the L change makes
it take effect?

thanks
-- PMM