Patch "powerpc/mm/radix: Properly clear process table entry" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

powerpc/mm/radix: Properly clear process table entry

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-mm-radix-properly-clear-process-table-entry.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Benjamin Herrenschmidt <[email protected]>
Date: Sat, 8 Jul 2017 07:45:32 -0500
Subject: powerpc/mm/radix: Properly clear process table entry

From: Benjamin Herrenschmidt <[email protected]>

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.

---
 arch/powerpc/mm/mmu_context_book3s64.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

@@ -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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/powerpc-mm-radix-properly-clear-process-table-entry.patch