powerpc/papr_scm: Use the correct bind address

When binding an SCM volume to a physical address the hypervisor has the
option to return early with a continue token with the expectation that
the guest will resume the bind operation until it completes. A quirk of
this interface is that the bind address will only be returned by the
first bind h-call and the subsequent calls will return
0xFFFF_FFFF_FFFF_FFFF for the bind address.

We currently do not save the address returned by the first h-call. As a
result we will use the junk address as the base of the bound region if
the hypervisor decides to split the bind across multiple h-calls. This
bug was found when testing with very large SCM volumes where the bind
process would take more time than they hypervisor's internal h-call time
limit would allow. This patch fixes the issue by saving the bind address
from the first call.

Cc: stable@vger.kernel.org
Fixes: b5beae5e224f ("powerpc/pseries: Add driver for PAPR SCM regions")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 7d6457ab5d3450f0db4d6cc25e2067c80db59f13..bba281b1fe1b0730f8a0d31fc469f324118a8933 100644 (file)
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -43,6 +43,7 @@ static int drc_pmem_bind(struct papr_scm_priv *p)
 {
        unsigned long ret[PLPAR_HCALL_BUFSIZE];
        uint64_t rc, token;
+       uint64_t saved = 0;
 
        /*
         * When the hypervisor cannot map all the requested memory in a single
@@ -56,6 +57,8 @@ static int drc_pmem_bind(struct papr_scm_priv *p)
                rc = plpar_hcall(H_SCM_BIND_MEM, ret, p->drc_index, 0,
                                p->blocks, BIND_ANY_ADDR, token);
                token = ret[0];
+               if (!saved)
+                       saved = ret[1];
                cond_resched();
        } while (rc == H_BUSY);
 
@@ -64,7 +67,7 @@ static int drc_pmem_bind(struct papr_scm_priv *p)
                return -ENXIO;
        }
 
-       p->bound_addr = ret[1];
+       p->bound_addr = saved;
 
        dev_dbg(&p->pdev->dev, "bound drc %x to %pR\n", p->drc_index, &p->res);