[PATCH v2 3/3] powerpc/papr_scm: Force a scm-unbind if initial scm-bind fails

[Oliver O'Halloran]

On Tue, Jun 25, 2019 at 10:27 PM Vaibhav Jain <vaibhav at linux.ibm.com> wrote:
>
> In some cases initial bind of scm memory for an lpar can fail if
> previously it wasn't released using a scm-unbind hcall. This situation
> can arise due to panic of the previous kernel or forced lpar
> fadump. In such cases the H_SCM_BIND_MEM return a H_OVERLAP error.
>
> To mitigate such cases the patch updates papr_scm_probe() to force a
> call to drc_pmem_unbind() in case the initial bind of scm memory fails
> with EBUSY error. In case scm-bind operation again fails after the
> forced scm-unbind then we follow the existing error path. We also
> update drc_pmem_bind() to handle the H_OVERLAP error returned by phyp
> and indicate it as a EBUSY error back to the caller.
>
> Suggested-by: "Oliver O'Halloran" <oohall at gmail.com>
> Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
> ---
> Change-log:
>
> v2:
> * Moved the retry code from drc_pmem_bind() to papr_scm_probe()
>   [Oliver]
> * Changed the type of variable 'rc' in drc_pmem_bind() to
>   int64_t. [Oliver]
> ---
>  arch/powerpc/platforms/pseries/papr_scm.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index a4e1674bb15c..2c90cbe88313 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -43,8 +43,9 @@ struct papr_scm_priv {
>  static int drc_pmem_bind(struct papr_scm_priv *p)
>  {
>         unsigned long ret[PLPAR_HCALL_BUFSIZE];
> -       uint64_t rc, token;
>         uint64_t saved = 0;
> +       uint64_t token;
> +       int64_t rc;
>
>         /*
>          * When the hypervisor cannot map all the requested memory in a single
> @@ -64,6 +65,10 @@ static int drc_pmem_bind(struct papr_scm_priv *p)
>         } while (rc == H_BUSY);
>
>         if (rc) {
> +               /* H_OVERLAP needs a separate error path */
> +               if (rc == H_OVERLAP)
> +                       return -EBUSY;
> +
>                 dev_err(&p->pdev->dev, "bind err: %lld\n", rc);
>                 return -ENXIO;
>         }
> @@ -331,6 +336,14 @@ static int papr_scm_probe(struct platform_device *pdev)
>
>         /* request the hypervisor to bind this region to somewhere in memory */
>         rc = drc_pmem_bind(p);
> +
> +       /* If phyp reports drc memory still bound the force unbound and retry */

"the force" should be "then force"?

> +       if (rc == -EBUSY) {
> +               dev_warn(&pdev->dev, "Retrying bind after unbinding\n");


Looks good otherwise,

Reviewed-by: Oliver O'Halloran <oohall at gmail.com>