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, 23 insertions, 12 deletions

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 67966f3..db4adf9 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1011,25 +1011,21 @@ static void build_get_ptep(u32 **p, unsigned int tmp, unsigned int ptr)
 
 static void build_update_entries(u32 **p, unsigned int tmp, unsigned int ptep)
 {
-	/*
-	 * 64bit address support (36bit on a 32bit CPU) in a 32bit
-	 * Kernel is a special case. Only a few CPUs use it.
-	 */
-	if (config_enabled(CONFIG_PHYS_ADDR_T_64BIT) && !cpu_has_64bits) {
+	if (config_enabled(CONFIG_XPA)) {
 		int pte_off_even = sizeof(pte_t) / 2;
 		int pte_off_odd = pte_off_even + sizeof(pte_t);
-#ifdef CONFIG_XPA
 		const int scratch = 1; /* Our extra working register */
 
 		uasm_i_addu(p, scratch, 0, ptep);
-#endif
+
 		uasm_i_lw(p, tmp, pte_off_even, ptep); /* even pte */
-		uasm_i_lw(p, ptep, pte_off_odd, ptep); /* odd pte */
 		UASM_i_ROTR(p, tmp, tmp, ilog2(_PAGE_GLOBAL));
-		UASM_i_ROTR(p, ptep, ptep, ilog2(_PAGE_GLOBAL));
 		UASM_i_MTC0(p, tmp, C0_ENTRYLO0);
+
+		uasm_i_lw(p, ptep, pte_off_odd, ptep); /* odd pte */
+		UASM_i_ROTR(p, ptep, ptep, ilog2(_PAGE_GLOBAL));
 		UASM_i_MTC0(p, ptep, C0_ENTRYLO1);
-#ifdef CONFIG_XPA
+
 		uasm_i_lw(p, tmp, 0, scratch);
 		uasm_i_lw(p, ptep, sizeof(pte_t), scratch);
 		uasm_i_lui(p, scratch, 0xff);
@@ -1038,7 +1034,22 @@ static void build_update_entries(u32 **p, unsigned int tmp, unsigned int ptep)
 		uasm_i_and(p, ptep, scratch, ptep);
 		uasm_i_mthc0(p, tmp, C0_ENTRYLO0);
 		uasm_i_mthc0(p, ptep, C0_ENTRYLO1);
-#endif
+		return;
+	}
+
+	/*
+	 * 64bit address support (36bit on a 32bit CPU) in a 32bit
+	 * Kernel is a special case. Only a few CPUs use it.
+	 */
+	if (config_enabled(CONFIG_PHYS_ADDR_T_64BIT) && !cpu_has_64bits) {
+		int pte_off_even = sizeof(pte_t) / 2;
+		int pte_off_odd = pte_off_even + sizeof(pte_t);
+
+		uasm_i_lw(p, tmp, pte_off_even, ptep); /* even pte */
+		UASM_i_MTC0(p, tmp, C0_ENTRYLO0);
+
+		uasm_i_lw(p, ptep, pte_off_odd, ptep); /* odd pte */
+		UASM_i_MTC0(p, ptep, C0_ENTRYLO1);
 		return;
 	}
 
@@ -1637,7 +1648,7 @@ iPTE_SW(u32 **p, struct uasm_reloc **r, unsigned int pte, unsigned int ptr,
 #ifdef CONFIG_PHYS_ADDR_T_64BIT
 	unsigned int hwmode = mode & (_PAGE_VALID | _PAGE_DIRTY);
 
-	if (!cpu_has_64bits) {
+	if (config_enabled(CONFIG_XPA) && !cpu_has_64bits) {
 		const int scratch = 1; /* Our extra working register */
 
 		uasm_i_lui(p, scratch, (mode >> 16));