powerpc/fsl_booke: Enable reloading of TLBCAM without switching to AS1

Avoid switching to AS1 when reloading TLBCAM after init for
STRICT_KERNEL_RWX.

When we setup AS1 we expect the entire accessible memory to be mapped
through one entry, this is not the case anymore at the end of init.

We are not changing the size of TLBCAMs, only flags, so no need to
switch to AS1.

So change loadcam_multi() to not switch to AS1 when the given
temporary tlb entry in 0.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a9d517fbfbc940f56103c46b323f6eb8f4485571.1634292136.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/mm/nohash/tlb_low.S b/arch/powerpc/mm/nohash/tlb_low.S
index 5add4a5..dd39074 100644 (file)
--- a/arch/powerpc/mm/nohash/tlb_low.S
+++ b/arch/powerpc/mm/nohash/tlb_low.S
@@ -369,7 +369,7 @@ _GLOBAL(_tlbivax_bcast)
  * extern void loadcam_entry(unsigned int index)
  *
  * Load TLBCAM[index] entry in to the L2 CAM MMU
- * Must preserve r7, r8, r9, r10 and r11
+ * Must preserve r7, r8, r9, r10, r11, r12
  */
 _GLOBAL(loadcam_entry)
        mflr    r5
@@ -401,7 +401,7 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_BIG_PHYS)
  *
  * r3 = first entry to write
  * r4 = number of entries to write
- * r5 = temporary tlb entry
+ * r5 = temporary tlb entry (0 means no switch to AS1)
  */
 _GLOBAL(loadcam_multi)
        mflr    r8
@@ -409,6 +409,8 @@ _GLOBAL(loadcam_multi)
        mfmsr   r11
        andi.   r11,r11,MSR_IS
        bne     10f
+       mr.     r12, r5
+       beq     10f
 
        /*
         * Set up temporary TLB entry that is the same as what we're
@@ -446,6 +448,8 @@ _GLOBAL(loadcam_multi)
        /* Don't return to AS=0 if we were in AS=1 at function start */
        andi.   r11,r11,MSR_IS
        bne     3f
+       cmpwi   r12, 0
+       beq     3f
 
        /* Return to AS=0 and clear the temporary entry */
        mfmsr   r6