[PATCH 5.15 126/159] powerpc/iommu: Limit number of TCEs to 512 for H_STUFF_TCE hcall

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From: Gaurav Batra <gbatra@xxxxxxxxxxxxxxxxxx>

commit 9d2ccf00bddc268045e3d65a8108d61ada0e4b4e upstream.

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: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gaurav Batra <gbatra@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Brian King <brking@xxxxxxxxxxxxxxxxxx>
[mpe: Tweak change log wording & add PAPR reference]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20230525143454.56878-1-gbatra@xxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/platforms/pseries/iommu.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -311,13 +311,22 @@ static void tce_free_pSeriesLP(unsigned
 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");





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