MIPS: mm: Fix MIPS32 36b physical addressing (alchemy, netlogic)

There are 2 distinct cases in which a kernel for a MIPS32 CPU
(CONFIG_CPU_MIPS32=y) may use 64 bit physical addresses
(CONFIG_PHYS_ADDR_T_64BIT=y):

  - 36 bit physical addressing as used by RMI Alchemy & Netlogic XLP/XLR
    CPUs.

  - MIPS32r5 eXtended Physical Addressing (XPA).

These 2 cases are distinct in that they require different behaviour from
the kernel - the EntryLo registers have different formats. Until Linux
v4.1 we only supported the first case, with code conditional upon the 2
aforementioned Kconfig variables being set. Commit c5b367835cfc ("MIPS:
Add support for XPA.") added support for the second case, but did so by
modifying the code that existed for the first case rather than treating
the 2 cases as distinct. Since the EntryLo registers have different
formats this breaks the 36 bit Alchemy/XLP/XLR case. Fix this by
splitting the 2 cases, with XPA cases now being conditional upon
CONFIG_XPA and the non-XPA case matching the code as it existed prior to
commit c5b367835cfc ("MIPS: Add support for XPA.").

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reported-by: Manuel Lauss <manuel.lauss@gmail.com>
Tested-by: Manuel Lauss <manuel.lauss@gmail.com>
Fixes: c5b367835cfc ("MIPS: Add support for XPA.")
Cc: James Hogan <james.hogan@imgtec.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Alex Smith <alex.smith@imgtec.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: stable@vger.kernel.org # v4.1+
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13119/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/arch/mips/include/asm/pgtable-bits.h b/arch/mips/include/asm/pgtable-bits.h
index 5bc663d330d2..58e8bf815404 100644
--- a/arch/mips/include/asm/pgtable-bits.h
+++ b/arch/mips/include/asm/pgtable-bits.h
@@ -32,11 +32,11 @@
  * unpredictable things.  The code (when it is written) to deal with
  * this problem will be in the update_mmu_cache() code for the r4k.
  */
-#if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
+#if defined(CONFIG_XPA)
 
 /*
- * Page table bit offsets used for 64 bit physical addressing on MIPS32,
- * for example with Alchemy, Netlogic XLP/XLR or XPA.
+ * Page table bit offsets used for 64 bit physical addressing on
+ * MIPS32r5 with XPA.
  */
 enum pgtable_bits {
 	/* Used by TLB hardware (placed in EntryLo*) */
@@ -59,6 +59,27 @@ enum pgtable_bits {
  */
 #define _PFNX_MASK		0xffffff
 
+#elif defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
+
+/*
+ * Page table bit offsets used for 36 bit physical addressing on MIPS32,
+ * for example with Alchemy or Netlogic XLP/XLR.
+ */
+enum pgtable_bits {
+	/* Used by TLB hardware (placed in EntryLo*) */
+	_PAGE_GLOBAL_SHIFT,
+	_PAGE_VALID_SHIFT,
+	_PAGE_DIRTY_SHIFT,
+	_CACHE_SHIFT,
+
+	/* Used only by software (masked out before writing EntryLo*) */
+	_PAGE_PRESENT_SHIFT = _CACHE_SHIFT + 3,
+	_PAGE_NO_READ_SHIFT,
+	_PAGE_WRITE_SHIFT,
+	_PAGE_ACCESSED_SHIFT,
+	_PAGE_MODIFIED_SHIFT,
+};
+
 #elif defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 
 /* Page table bits used for r3k systems */
@@ -116,7 +137,7 @@ enum pgtable_bits {
 #endif
 
 /* Used by TLB hardware (placed in EntryLo*) */
-#if (defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32))
+#if defined(CONFIG_XPA)
 # define _PAGE_NO_EXEC		(1 << _PAGE_NO_EXEC_SHIFT)
 #elif defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6)
 # define _PAGE_NO_EXEC		(cpu_has_rixi ? (1 << _PAGE_NO_EXEC_SHIFT) : 0)