powerpc/papr_scm: Force a scm-unbind if initial scm-bind fails

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@gmail.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190629160610.23402-4-vaibhav@linux.ibm.com

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 82568a7..2c07908 100644 (file)
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -44,8 +44,9 @@ 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
@@ -65,6 +66,10 @@ 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;
        }
@@ -404,6 +409,14 @@ 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 says drc memory still bound then force unbound and retry */
+       if (rc == -EBUSY) {
+               dev_warn(&pdev->dev, "Retrying bind after unbinding\n");
+               drc_pmem_unbind(p);
+               rc = drc_pmem_bind(p);
+       }
+
        if (rc)
                goto err;