4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
commit c6bb0b8d426a8cf865ca9c8a532cc3a2927cfceb upstream.
On radix, the process table entry we want to clear when destroying a
context is entry 0, not entry 1. This has no *immediate* consequence
on Power9, but it can cause other bugs to become worse.
Fixes: 7e381c0ff618 ("powerpc/mm/radix: Add mmu context handling callback for radix")
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/mm/mmu_context_book3s64.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -167,9 +167,15 @@ void destroy_context(struct mm_struct *m
mm->context.cop_lockp = NULL;
#endif /* CONFIG_PPC_ICSWX */
- if (radix_enabled())
- process_tb[mm->context.id].prtb1 = 0;
- else
+ if (radix_enabled()) {
+ /*
+ * Radix doesn't have a valid bit in the process table
+ * entries. However we know that at least P9 implementation
+ * will avoid caching an entry with an invalid RTS field,
+ * and 0 is invalid. So this will do.
+ */
+ process_tb[mm->context.id].prtb0 = 0;
+ } else
subpage_prot_free(mm);
destroy_pagetable_page(mm);
__destroy_context(mm->context.id);