[PATCH] powerpc/papr_scm: Use the correct bind address

[Oliver O'Halloran]

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 at vger.kernel.org
Fixes: b5beae5e224f ("powerpc/pseries: Add driver for PAPR SCM regions")
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 arch/powerpc/platforms/pseries/papr_scm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 7d6457ab5d34..bba281b1fe1b 100644
--- 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);
 
-- 
2.20.1