[PATCH v2] powerpc/iommu: limit number of TCEs to 512 for H_STUFF_TCE hcall

[Gaurav Batra <gbatra@linux.vnet.ibm.com>]

As of now, in tce_freemulti_pSeriesLP(), there is no limit on how many TCEs
are passed to H_STUFF_TCE hcall. This was not an issue until now. Newer
firmware releases have started enforcing this requirement.

The interface has been in it's current form since the beginning.

Cc: stable@vger.kernel.org

Signed-off-by: Gaurav Batra <gbatra@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index c74b71d4733d..f159a195101d 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -306,13 +306,22 @@ static void tce_free_pSeriesLP(unsigned long liobn, long tcenum, long tceshift,
 static void tce_freemulti_pSeriesLP(struct iommu_table *tbl, long tcenum, long npages)
 {
 	u64 rc;
+	long rpages = npages;
+	unsigned long limit;
 
 	if (!firmware_has_feature(FW_FEATURE_STUFF_TCE))
 		return tce_free_pSeriesLP(tbl->it_index, tcenum,
 					  tbl->it_page_shift, npages);
 
-	rc = plpar_tce_stuff((u64)tbl->it_index,
-			     (u64)tcenum << tbl->it_page_shift, 0, npages);
+	do {
+		limit = min_t(unsigned long, rpages, 512);
+
+		rc = plpar_tce_stuff((u64)tbl->it_index,
+			     	(u64)tcenum << tbl->it_page_shift, 0, limit);
+
+		rpages -= limit;
+		tcenum += limit;
+	} while (rpages > 0 && !rc);
 
 	if (rc && printk_ratelimit()) {
 		printk("tce_freemulti_pSeriesLP: plpar_tce_stuff failed\n");
-- 
2.39.2 (Apple Git-143)