Patch "parisc: Remove unnecessary TLB purges from flush_dcache_page_asm and flush_icache_page_asm" has been added to the 4.8-stable tree

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

parisc: Remove unnecessary TLB purges from flush_dcache_page_asm and flush_icache_page_asm

to the 4.8-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:
parisc-remove-unnecessary-tlb-purges-from-flush_dcache_page_asm-and-flush_icache_page_asm.patch
and it can be found in the queue-4.8 subdirectory.

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

From: John David Anglin <[email protected]>
Date: Tue, 6 Dec 2016 22:02:01 -0500
Subject: parisc: Remove unnecessary TLB purges from flush_dcache_page_asm and flush_icache_page_asm

From: John David Anglin <[email protected]>

commit febe42964fe182281859b3d43d844bb25ca49367 upstream.

We have four routines in pacache.S that use temporary alias pages:
copy_user_page_asm(), clear_user_page_asm(), flush_dcache_page_asm() and flush_icache_page_asm(). copy_user_page_asm() and clear_user_page_asm() don't purge the TLB entry used for the operation. flush_dcache_page_asm() and flush_icache_page_asm do purge the entry.

Presumably, this was thought to optimize TLB use. However, the operation is quite heavy weight on PA 1.X processors as we need to take the TLB lock and a TLB broadcast is sent to all processors.

This patch removes the purges from flush_dcache_page_asm() and flush_icache_page_asm.

---
 arch/parisc/kernel/pacache.S |   22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

@@ -886,19 +886,10 @@ ENTRY(flush_dcache_page_asm)
 	fdc,m		r31(%r28)
 	fdc,m		r31(%r28)
 	fdc,m		r31(%r28)
-	cmpb,COND(<<)		%r28, %r25,1b
+	cmpb,COND(<<)	%r28, %r25,1b
 	fdc,m		r31(%r28)
 
 	sync
-
-#ifdef CONFIG_PA20
-	pdtlb,l		%r0(%r25)
-#else
-	tlb_lock	%r20,%r21,%r22
-	pdtlb		%r0(%r25)
-	tlb_unlock	%r20,%r21,%r22
-#endif
-
 	bv		%r0(%r2)
 	nop
 	.exit

@@ -973,17 +964,6 @@ ENTRY(flush_icache_page_asm)
 	fic,m		%r31(%sr4,%r28)
 
 	sync
-
-#ifdef CONFIG_PA20
-	pdtlb,l		%r0(%r28)
-	pitlb,l         %r0(%sr4,%r25)
-#else
-	tlb_lock        %r20,%r21,%r22
-	pdtlb		%r0(%r28)
-	pitlb           %r0(%sr4,%r25)
-	tlb_unlock      %r20,%r21,%r22
-#endif
-
 	bv		%r0(%r2)
 	nop
 	.exit

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

queue-4.8/parisc-remove-unnecessary-tlb-purges-from-flush_dcache_page_asm-and-flush_icache_page_asm.patch queue-4.8/parisc-purge-tlb-before-setting-pte.patch