powerpc/iommu: Limit number of TCEs to 512 for H_STUFF_TCE hcall

Currently in tce_freemulti_pSeriesLP() there is no limit on how many TCEs are passed to the H_STUFF_TCE hcall. This has not caused an issue until now, but newer firmware releases have started enforcing a limit of 512 TCEs per call. The limit is correct per the specification (PAPR v2.12 § 14.5.4.2.3). The code has been in it's current form since it was initially merged. Cc: [email protected] Signed-off-by: Gaurav Batra <[email protected]> Reviewed-by: Brian King <[email protected]> [mpe: Tweak change log wording & add PAPR reference] Signed-off-by: Michael Ellerman <[email protected]> Link: https://msgid.link/[email protected]
jbrandeb · May 30, 2023 · 9d2ccf0 · 9d2ccf0
1 parent 81d358b
commit 9d2ccf0
Showing 1 changed file with 11 additions and 2 deletions.
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
@@ -317,13 +317,22 @@ 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");