linux-kernel - [PATCH 5.5 237/257] powerpc/fsl_booke: Avoid creating duplicate tlb1 entry

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Message-Id: <20200416131355.209900249@linuxfoundation.org>
Date:   Thu, 16 Apr 2020 15:24:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Laurentiu Tudor <laurentiu.tudor@....com>,
        Scott Wood <oss@...error.net>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.5 237/257] powerpc/fsl_booke: Avoid creating duplicate tlb1 entry

From: Laurentiu Tudor <laurentiu.tudor@....com>

commit aa4113340ae6c2811e046f08c2bc21011d20a072 upstream.

In the current implementation, the call to loadcam_multi() is wrapped
between switch_to_as1() and restore_to_as0() calls so, when it tries
to create its own temporary AS=1 TLB1 entry, it ends up duplicating
the existing one created by switch_to_as1(). Add a check to skip
creating the temporary entry if already running in AS=1.

Fixes: d9e1831a4202 ("powerpc/85xx: Load all early TLB entries at once")
Cc: stable@...r.kernel.org # v4.4+
Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
Acked-by: Scott Wood <oss@...error.net>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20200123111914.2565-1-laurentiu.tudor@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/mm/nohash/tlb_low.S |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/arch/powerpc/mm/nohash/tlb_low.S
+++ b/arch/powerpc/mm/nohash/tlb_low.S
@@ -397,7 +397,7 @@ _GLOBAL(set_context)
  * extern void loadcam_entry(unsigned int index)
  *
  * Load TLBCAM[index] entry in to the L2 CAM MMU
- * Must preserve r7, r8, r9, and r10
+ * Must preserve r7, r8, r9, r10 and r11
  */
 _GLOBAL(loadcam_entry)
 	mflr	r5
@@ -433,6 +433,10 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_BIG_PH
  */
 _GLOBAL(loadcam_multi)
 	mflr	r8
+	/* Don't switch to AS=1 if already there */
+	mfmsr	r11
+	andi.	r11,r11,MSR_IS
+	bne	10f
 
 	/*
 	 * Set up temporary TLB entry that is the same as what we're
@@ -458,6 +462,7 @@ _GLOBAL(loadcam_multi)
 	mtmsr	r6
 	isync
 
+10:
 	mr	r9,r3
 	add	r10,r3,r4
 2:	bl	loadcam_entry
@@ -466,6 +471,10 @@ _GLOBAL(loadcam_multi)
 	mr	r3,r9
 	blt	2b
 
+	/* Don't return to AS=0 if we were in AS=1 at function start */
+	andi.	r11,r11,MSR_IS
+	bne	3f
+
 	/* Return to AS=0 and clear the temporary entry */
 	mfmsr	r6
 	rlwinm.	r6,r6,0,~(MSR_IS|MSR_DS)
@@ -481,6 +490,7 @@ _GLOBAL(loadcam_multi)
 	tlbwe
 	isync
 
+3:
 	mtlr	r8
 	blr
 #endif