powerpc/mm/radix: Properly clear process table entry

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@kernel.crashing.org>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 73bf6e14c3aa04c082921c3691c2cd48320c2892..a006f822b1540f0755de1bfdb3ef4e9e137eb6cc 100644 (file)
--- 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 *mm)
        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);