MIPS: 64-bit: Detect virtual memory size

Linux kernel 2.6.32 and later allocate address space from the top of the
kernel virtual memory address space.

This patch implements virtual memory size detection for 64 bit MIPS CPUs
to avoid resulting crashes.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/935/
Reviewed-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

4 files changed, 24 insertions, 1 deletions

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 1f4df647c384..272c5ef35bbb 100644
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -191,6 +191,9 @@
 # ifndef cpu_has_64bit_addresses
 # define cpu_has_64bit_addresses        0
 # endif
+# ifndef cpu_vmbits
+# define cpu_vmbits 31
+# endif
 #endif
 
 #ifdef CONFIG_64BIT
@@ -209,6 +212,10 @@
 # ifndef cpu_has_64bit_addresses
 # define cpu_has_64bit_addresses        1
 # endif
+# ifndef cpu_vmbits
+# define cpu_vmbits cpu_data[0].vmbits
+# define __NEED_VMBITS_PROBE
+# endif
 #endif
 
 #if defined(CONFIG_CPU_MIPSR2_IRQ_VI) && !defined(cpu_has_vint)
diff --git a/arch/mips/include/asm/cpu-info.h b/arch/mips/include/asm/cpu-info.h
index 126044308dec..b39def3f6e03 100644
--- a/arch/mips/include/asm/cpu-info.h
+++ b/arch/mips/include/asm/cpu-info.h
@@ -58,6 +58,9 @@ struct cpuinfo_mips {
         struct cache_desc       tcache; /* Tertiary/split secondary cache */
         int                     srsets; /* Shadow register sets */
         int                     core;   /* physical core number */
+#ifdef CONFIG_64BIT
+        int                     vmbits; /* Virtual memory size in bits */
+#endif
 #if defined(CONFIG_MIPS_MT_SMP) || defined(CONFIG_MIPS_MT_SMTC)
         /*
          * In the MIPS MT "SMTC" model, each TC is considered
diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 9cd508993956..8eda30b467da 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -110,7 +110,9 @@
 #define VMALLOC_START           MAP_BASE
 #define VMALLOC_END     \
         (VMALLOC_START + \
-         PTRS_PER_PGD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE - (1UL << 32))
+         min(PTRS_PER_PGD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE, \
+             (1UL << cpu_vmbits)) - (1UL << 32))
+
 #if defined(CONFIG_MODULES) && defined(KBUILD_64BIT_SYM32) && \
         VMALLOC_START != CKSSEG
 /* Load modules into 32bit-compatible segment. */
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 80e202eca056..9c187a64649b 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -284,6 +284,15 @@ static inline int __cpu_has_fpu(void)
         return ((cpu_get_fpu_id() & 0xff00) != FPIR_IMP_NONE);
 }
 
+static inline void cpu_probe_vmbits(struct cpuinfo_mips *c)
+{
+#ifdef __NEED_VMBITS_PROBE
+        write_c0_entryhi(0x3ffffffffffff000ULL);
+        back_to_back_c0_hazard();
+        c->vmbits = fls64(read_c0_entryhi() & 0x3ffffffffffff000ULL);
+#endif
+}
+
 #define R4K_OPTS (MIPS_CPU_TLB | MIPS_CPU_4KEX | MIPS_CPU_4K_CACHE \
                 | MIPS_CPU_COUNTER)
 
@@ -969,6 +978,8 @@ __cpuinit void cpu_probe(void)
                 c->srsets = ((read_c0_srsctl() >> 26) & 0x0f) + 1;
         else
                 c->srsets = 1;
+
+        cpu_probe_vmbits(c);
 }
 
 __cpuinit void cpu_report(void)