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authorSteven J. Hill2013-03-25 11:58:57 -0500
committerRalf Baechle2013-05-08 12:30:10 +0200
commitd532f3d26716a39dfd4b88d687bd344fbe77e390 (patch)
tree64bb16ffd8176e0c9e692817b1d17df717c127ed /arch
parent49bffbdc88fdd8f5eac40306a617252625a0fa35 (diff)
MIPS: Allow ASID size to be determined at boot time.
Original patch by Ralf Baechle and removed by Harold Koerfgen with commit f67e4ffc79905482c3b9b8c8dd65197bac7eb508. This allows for more generic kernels since the size of the ASID and corresponding masks can be determined at run-time. This patch is also required for the new Aptiv cores and has been tested on Malta and Malta Aptiv platforms. [ralf@linux-mips.org: Added relevant part of fix https://patchwork.linux-mips.org/patch/5213/] Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/mips/include/asm/mmu_context.h95
-rw-r--r--arch/mips/kernel/genex.S2
-rw-r--r--arch/mips/kernel/smtc.c10
-rw-r--r--arch/mips/kernel/traps.c6
-rw-r--r--arch/mips/lib/dump_tlb.c5
-rw-r--r--arch/mips/lib/r3k_dump_tlb.c7
-rw-r--r--arch/mips/mm/tlb-r3k.c20
-rw-r--r--arch/mips/mm/tlb-r4k.c2
-rw-r--r--arch/mips/mm/tlb-r8k.c2
-rw-r--r--arch/mips/mm/tlbex.c49
10 files changed, 137 insertions, 61 deletions
diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h
index e81d719efcd1..bab1980bbf0d 100644
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -62,45 +62,68 @@ extern unsigned long pgd_current[];
TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir)
#endif
#endif /* CONFIG_MIPS_PGD_C0_CONTEXT*/
-#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
-#define ASID_INC 0x40
-#define ASID_MASK 0xfc0
-
-#elif defined(CONFIG_CPU_R8000)
-
-#define ASID_INC 0x10
-#define ASID_MASK 0xff0
-
-#elif defined(CONFIG_MIPS_MT_SMTC)
-
-#define ASID_INC 0x1
-extern unsigned long smtc_asid_mask;
-#define ASID_MASK (smtc_asid_mask)
-#define HW_ASID_MASK 0xff
-/* End SMTC/34K debug hack */
-#else /* FIXME: not correct for R6000 */
-
-#define ASID_INC 0x1
-#define ASID_MASK 0xff
+#define ASID_INC(asid) \
+({ \
+ unsigned long __asid = asid; \
+ __asm__("1:\taddiu\t%0,1\t\t\t\t# patched\n\t" \
+ ".section\t__asid_inc,\"a\"\n\t" \
+ ".word\t1b\n\t" \
+ ".previous" \
+ :"=r" (__asid) \
+ :"0" (__asid)); \
+ __asid; \
+})
+#define ASID_MASK(asid) \
+({ \
+ unsigned long __asid = asid; \
+ __asm__("1:\tandi\t%0,%1,0xfc0\t\t\t# patched\n\t" \
+ ".section\t__asid_mask,\"a\"\n\t" \
+ ".word\t1b\n\t" \
+ ".previous" \
+ :"=r" (__asid) \
+ :"r" (__asid)); \
+ __asid; \
+})
+#define ASID_VERSION_MASK \
+({ \
+ unsigned long __asid; \
+ __asm__("1:\taddiu\t%0,$0,0xff00\t\t\t\t# patched\n\t" \
+ ".section\t__asid_version_mask,\"a\"\n\t" \
+ ".word\t1b\n\t" \
+ ".previous" \
+ :"=r" (__asid)); \
+ __asid; \
+})
+#define ASID_FIRST_VERSION \
+({ \
+ unsigned long __asid = asid; \
+ __asm__("1:\tli\t%0,0x100\t\t\t\t# patched\n\t" \
+ ".section\t__asid_first_version,\"a\"\n\t" \
+ ".word\t1b\n\t" \
+ ".previous" \
+ :"=r" (__asid)); \
+ __asid; \
+})
+
+#define ASID_FIRST_VERSION_R3000 0x1000
+#define ASID_FIRST_VERSION_R4000 0x100
+#define ASID_FIRST_VERSION_R8000 0x1000
+#define ASID_FIRST_VERSION_RM9000 0x1000
+#ifdef CONFIG_MIPS_MT_SMTC
+#define SMTC_HW_ASID_MASK 0xff
+extern unsigned int smtc_asid_mask;
#endif
#define cpu_context(cpu, mm) ((mm)->context.asid[cpu])
-#define cpu_asid(cpu, mm) (cpu_context((cpu), (mm)) & ASID_MASK)
+#define cpu_asid(cpu, mm) ASID_MASK(cpu_context((cpu), (mm)))
#define asid_cache(cpu) (cpu_data[cpu].asid_cache)
static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}
-/*
- * All unused by hardware upper bits will be considered
- * as a software asid extension.
- */
-#define ASID_VERSION_MASK ((unsigned long)~(ASID_MASK|(ASID_MASK-1)))
-#define ASID_FIRST_VERSION ((unsigned long)(~ASID_VERSION_MASK) + 1)
-
#ifndef CONFIG_MIPS_MT_SMTC
/* Normal, classic MIPS get_new_mmu_context */
static inline void
@@ -108,7 +131,7 @@ get_new_mmu_context(struct mm_struct *mm, unsigned long cpu)
{
unsigned long asid = asid_cache(cpu);
- if (! ((asid += ASID_INC) & ASID_MASK) ) {
+ if (!ASID_MASK((asid = ASID_INC(asid)))) {
if (cpu_has_vtag_icache)
flush_icache_all();
local_flush_tlb_all(); /* start new asid cycle */
@@ -166,7 +189,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
* free up the ASID value for use and flush any old
* instances of it from the TLB.
*/
- oldasid = (read_c0_entryhi() & ASID_MASK);
+ oldasid = ASID_MASK(read_c0_entryhi());
if(smtc_live_asid[mytlb][oldasid]) {
smtc_live_asid[mytlb][oldasid] &= ~(0x1 << cpu);
if(smtc_live_asid[mytlb][oldasid] == 0)
@@ -177,7 +200,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
* having ASID_MASK smaller than the hardware maximum,
* make sure no "soft" bits become "hard"...
*/
- write_c0_entryhi((read_c0_entryhi() & ~HW_ASID_MASK) |
+ write_c0_entryhi((read_c0_entryhi() & ~SMTC_HW_ASID_MASK) |
cpu_asid(cpu, next));
ehb(); /* Make sure it propagates to TCStatus */
evpe(mtflags);
@@ -230,15 +253,15 @@ activate_mm(struct mm_struct *prev, struct mm_struct *next)
#ifdef CONFIG_MIPS_MT_SMTC
/* See comments for similar code above */
mtflags = dvpe();
- oldasid = read_c0_entryhi() & ASID_MASK;
+ oldasid = ASID_MASK(read_c0_entryhi());
if(smtc_live_asid[mytlb][oldasid]) {
smtc_live_asid[mytlb][oldasid] &= ~(0x1 << cpu);
if(smtc_live_asid[mytlb][oldasid] == 0)
smtc_flush_tlb_asid(oldasid);
}
/* See comments for similar code above */
- write_c0_entryhi((read_c0_entryhi() & ~HW_ASID_MASK) |
- cpu_asid(cpu, next));
+ write_c0_entryhi((read_c0_entryhi() & ~SMTC_HW_ASID_MASK) |
+ cpu_asid(cpu, next));
ehb(); /* Make sure it propagates to TCStatus */
evpe(mtflags);
#else
@@ -275,14 +298,14 @@ drop_mmu_context(struct mm_struct *mm, unsigned cpu)
#ifdef CONFIG_MIPS_MT_SMTC
/* See comments for similar code above */
prevvpe = dvpe();
- oldasid = (read_c0_entryhi() & ASID_MASK);
+ oldasid = ASID_MASK(read_c0_entryhi());
if (smtc_live_asid[mytlb][oldasid]) {
smtc_live_asid[mytlb][oldasid] &= ~(0x1 << cpu);
if(smtc_live_asid[mytlb][oldasid] == 0)
smtc_flush_tlb_asid(oldasid);
}
/* See comments for similar code above */
- write_c0_entryhi((read_c0_entryhi() & ~HW_ASID_MASK)
+ write_c0_entryhi((read_c0_entryhi() & ~SMTC_HW_ASID_MASK)
| cpu_asid(cpu, mm));
ehb(); /* Make sure it propagates to TCStatus */
evpe(prevvpe);
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index ecb347ce1b3d..5360b1db337d 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -480,7 +480,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
.set noreorder
/* check if TLB contains a entry for EPC */
MFC0 k1, CP0_ENTRYHI
- andi k1, 0xff /* ASID_MASK */
+ andi k1, 0xff /* ASID_MASK patched at run-time!! */
MFC0 k0, CP0_EPC
PTR_SRL k0, _PAGE_SHIFT + 1
PTR_SLL k0, _PAGE_SHIFT + 1
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c
index 7186222dc5bb..31d22f3121c9 100644
--- a/arch/mips/kernel/smtc.c
+++ b/arch/mips/kernel/smtc.c
@@ -111,7 +111,7 @@ static int vpe0limit;
static int ipibuffers;
static int nostlb;
static int asidmask;
-unsigned long smtc_asid_mask = 0xff;
+unsigned int smtc_asid_mask = 0xff;
static int __init vpe0tcs(char *str)
{
@@ -1395,7 +1395,7 @@ void smtc_get_new_mmu_context(struct mm_struct *mm, unsigned long cpu)
asid = asid_cache(cpu);
do {
- if (!((asid += ASID_INC) & ASID_MASK) ) {
+ if (!ASID_MASK(ASID_INC(asid))) {
if (cpu_has_vtag_icache)
flush_icache_all();
/* Traverse all online CPUs (hack requires contiguous range) */
@@ -1414,7 +1414,7 @@ void smtc_get_new_mmu_context(struct mm_struct *mm, unsigned long cpu)
mips_ihb();
}
tcstat = read_tc_c0_tcstatus();
- smtc_live_asid[tlb][(tcstat & ASID_MASK)] |= (asiduse)(0x1 << i);
+ smtc_live_asid[tlb][ASID_MASK(tcstat)] |= (asiduse)(0x1 << i);
if (!prevhalt)
write_tc_c0_tchalt(0);
}
@@ -1423,7 +1423,7 @@ void smtc_get_new_mmu_context(struct mm_struct *mm, unsigned long cpu)
asid = ASID_FIRST_VERSION;
local_flush_tlb_all(); /* start new asid cycle */
}
- } while (smtc_live_asid[tlb][(asid & ASID_MASK)]);
+ } while (smtc_live_asid[tlb][ASID_MASK(asid)]);
/*
* SMTC shares the TLB within VPEs and possibly across all VPEs.
@@ -1461,7 +1461,7 @@ void smtc_flush_tlb_asid(unsigned long asid)
tlb_read();
ehb();
ehi = read_c0_entryhi();
- if ((ehi & ASID_MASK) == asid) {
+ if (ASID_MASK(ehi) == asid) {
/*
* Invalidate only entries with specified ASID,
* makiing sure all entries differ.
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index c3abb88170fc..4b6b607b0179 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1547,6 +1547,7 @@ void __cpuinit per_cpu_trap_init(bool is_boot_cpu)
unsigned int cpu = smp_processor_id();
unsigned int status_set = ST0_CU0;
unsigned int hwrena = cpu_hwrena_impl_bits;
+ unsigned long asid = 0;
#ifdef CONFIG_MIPS_MT_SMTC
int secondaryTC = 0;
int bootTC = (cpu == 0);
@@ -1630,8 +1631,9 @@ void __cpuinit per_cpu_trap_init(bool is_boot_cpu)
}
#endif /* CONFIG_MIPS_MT_SMTC */
- if (!cpu_data[cpu].asid_cache)
- cpu_data[cpu].asid_cache = ASID_FIRST_VERSION;
+ asid = ASID_FIRST_VERSION;
+ cpu_data[cpu].asid_cache = asid;
+ TLBMISS_HANDLER_SETUP();
atomic_inc(&init_mm.mm_count);
current->active_mm = &init_mm;
diff --git a/arch/mips/lib/dump_tlb.c b/arch/mips/lib/dump_tlb.c
index 32b9f21bfd85..8a12d00908e0 100644
--- a/arch/mips/lib/dump_tlb.c
+++ b/arch/mips/lib/dump_tlb.c
@@ -11,6 +11,7 @@
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/tlbdebug.h>
+#include <asm/mmu_context.h>
static inline const char *msk2str(unsigned int mask)
{
@@ -55,7 +56,7 @@ static void dump_tlb(int first, int last)
s_pagemask = read_c0_pagemask();
s_entryhi = read_c0_entryhi();
s_index = read_c0_index();
- asid = s_entryhi & 0xff;
+ asid = ASID_MASK(s_entryhi);
for (i = first; i <= last; i++) {
write_c0_index(i);
@@ -85,7 +86,7 @@ static void dump_tlb(int first, int last)
printk("va=%0*lx asid=%02lx\n",
width, (entryhi & ~0x1fffUL),
- entryhi & 0xff);
+ ASID_MASK(entryhi));
printk("\t[pa=%0*llx c=%d d=%d v=%d g=%d] ",
width,
(entrylo0 << 6) & PAGE_MASK, c0,
diff --git a/arch/mips/lib/r3k_dump_tlb.c b/arch/mips/lib/r3k_dump_tlb.c
index 91615c2ef0cf..8327698b9937 100644
--- a/arch/mips/lib/r3k_dump_tlb.c
+++ b/arch/mips/lib/r3k_dump_tlb.c
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <asm/mipsregs.h>
+#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/tlbdebug.h>
@@ -21,7 +22,7 @@ static void dump_tlb(int first, int last)
unsigned int asid;
unsigned long entryhi, entrylo0;
- asid = read_c0_entryhi() & 0xfc0;
+ asid = ASID_MASK(read_c0_entryhi());
for (i = first; i <= last; i++) {
write_c0_index(i<<8);
@@ -35,7 +36,7 @@ static void dump_tlb(int first, int last)
/* Unused entries have a virtual address of KSEG0. */
if ((entryhi & 0xffffe000) != 0x80000000
- && (entryhi & 0xfc0) == asid) {
+ && (ASID_MASK(entryhi) == asid)) {
/*
* Only print entries in use
*/
@@ -44,7 +45,7 @@ static void dump_tlb(int first, int last)
printk("va=%08lx asid=%08lx"
" [pa=%06lx n=%d d=%d v=%d g=%d]",
(entryhi & 0xffffe000),
- entryhi & 0xfc0,
+ ASID_MASK(entryhi),
entrylo0 & PAGE_MASK,
(entrylo0 & (1 << 11)) ? 1 : 0,
(entrylo0 & (1 << 10)) ? 1 : 0,
diff --git a/arch/mips/mm/tlb-r3k.c b/arch/mips/mm/tlb-r3k.c
index a63d1ed0827f..4a13c150f31b 100644
--- a/arch/mips/mm/tlb-r3k.c
+++ b/arch/mips/mm/tlb-r3k.c
@@ -51,7 +51,7 @@ void local_flush_tlb_all(void)
#endif
local_irq_save(flags);
- old_ctx = read_c0_entryhi() & ASID_MASK;
+ old_ctx = ASID_MASK(read_c0_entryhi());
write_c0_entrylo0(0);
entry = r3k_have_wired_reg ? read_c0_wired() : 8;
for (; entry < current_cpu_data.tlbsize; entry++) {
@@ -87,13 +87,13 @@ void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
#ifdef DEBUG_TLB
printk("[tlbrange<%lu,0x%08lx,0x%08lx>]",
- cpu_context(cpu, mm) & ASID_MASK, start, end);
+ ASID_MASK(cpu_context(cpu, mm)), start, end);
#endif
local_irq_save(flags);
size = (end - start + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
if (size <= current_cpu_data.tlbsize) {
- int oldpid = read_c0_entryhi() & ASID_MASK;
- int newpid = cpu_context(cpu, mm) & ASID_MASK;
+ int oldpid = ASID_MASK(read_c0_entryhi());
+ int newpid = ASID_MASK(cpu_context(cpu, mm));
start &= PAGE_MASK;
end += PAGE_SIZE - 1;
@@ -166,10 +166,10 @@ void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
#ifdef DEBUG_TLB
printk("[tlbpage<%lu,0x%08lx>]", cpu_context(cpu, vma->vm_mm), page);
#endif
- newpid = cpu_context(cpu, vma->vm_mm) & ASID_MASK;
+ newpid = ASID_MASK(cpu_context(cpu, vma->vm_mm));
page &= PAGE_MASK;
local_irq_save(flags);
- oldpid = read_c0_entryhi() & ASID_MASK;
+ oldpid = ASID_MASK(read_c0_entryhi());
write_c0_entryhi(page | newpid);
BARRIER;
tlb_probe();
@@ -197,10 +197,10 @@ void __update_tlb(struct vm_area_struct *vma, unsigned long address, pte_t pte)
if (current->active_mm != vma->vm_mm)
return;
- pid = read_c0_entryhi() & ASID_MASK;
+ pid = ASID_MASK(read_c0_entryhi());
#ifdef DEBUG_TLB
- if ((pid != (cpu_context(cpu, vma->vm_mm) & ASID_MASK)) || (cpu_context(cpu, vma->vm_mm) == 0)) {
+ if ((pid != ASID_MASK(cpu_context(cpu, vma->vm_mm))) || (cpu_context(cpu, vma->vm_mm) == 0)) {
printk("update_mmu_cache: Wheee, bogus tlbpid mmpid=%lu tlbpid=%d\n",
(cpu_context(cpu, vma->vm_mm)), pid);
}
@@ -241,7 +241,7 @@ void add_wired_entry(unsigned long entrylo0, unsigned long entrylo1,
local_irq_save(flags);
/* Save old context and create impossible VPN2 value */
- old_ctx = read_c0_entryhi() & ASID_MASK;
+ old_ctx = ASID_MASK(read_c0_entryhi());
old_pagemask = read_c0_pagemask();
w = read_c0_wired();
write_c0_wired(w + 1);
@@ -264,7 +264,7 @@ void add_wired_entry(unsigned long entrylo0, unsigned long entrylo1,
#endif
local_irq_save(flags);
- old_ctx = read_c0_entryhi() & ASID_MASK;
+ old_ctx = ASID_MASK(read_c0_entryhi());
write_c0_entrylo0(entrylo0);
write_c0_entryhi(entryhi);
write_c0_index(wired);
diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 493131c81a29..3d03a2ccebaa 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -285,7 +285,7 @@ void __update_tlb(struct vm_area_struct * vma, unsigned long address, pte_t pte)
ENTER_CRITICAL(flags);
- pid = read_c0_entryhi() & ASID_MASK;
+ pid = ASID_MASK(read_c0_entryhi());
address &= (PAGE_MASK << 1);
write_c0_entryhi(address | pid);
pgdp = pgd_offset(vma->vm_mm, address);
diff --git a/arch/mips/mm/tlb-r8k.c b/arch/mips/mm/tlb-r8k.c
index 91c2499f806a..122f9207f49e 100644
--- a/arch/mips/mm/tlb-r8k.c
+++ b/arch/mips/mm/tlb-r8k.c
@@ -195,7 +195,7 @@ void __update_tlb(struct vm_area_struct * vma, unsigned long address, pte_t pte)
if (current->active_mm != vma->vm_mm)
return;
- pid = read_c0_entryhi() & ASID_MASK;
+ pid = ASID_MASK(read_c0_entryhi());
local_irq_save(flags);
address &= PAGE_MASK;
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 820e6612d744..e2a9e3687c45 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -29,6 +29,7 @@
#include <linux/init.h>
#include <linux/cache.h>
+#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/pgtable.h>
#include <asm/war.h>
@@ -305,6 +306,48 @@ static struct uasm_reloc relocs[128] __cpuinitdata;
static int check_for_high_segbits __cpuinitdata;
#endif
+static void __cpuinit insn_fixup(unsigned int **start, unsigned int **stop,
+ unsigned int i_const)
+{
+ unsigned int **p, *ip;
+
+ for (p = start; p < stop; p++) {
+ ip = *p;
+ *ip = (*ip & 0xffff0000) | i_const;
+ }
+ local_flush_icache_range((unsigned long)*p, (unsigned long)((*p) + 1));
+}
+
+#define asid_insn_fixup(section, const) \
+do { \
+ extern unsigned int *__start_ ## section; \
+ extern unsigned int *__stop_ ## section; \
+ insn_fixup(&__start_ ## section, &__stop_ ## section, const); \
+} while(0)
+
+/*
+ * Caller is assumed to flush the caches before the first context switch.
+ */
+static void __cpuinit setup_asid(unsigned int inc, unsigned int mask,
+ unsigned int version_mask,
+ unsigned int first_version)
+{
+ extern asmlinkage void handle_ri_rdhwr_vivt(void);
+ unsigned long *vivt_exc;
+
+ asid_insn_fixup(__asid_inc, inc);
+ asid_insn_fixup(__asid_mask, mask);
+ asid_insn_fixup(__asid_version_mask, version_mask);
+ asid_insn_fixup(__asid_first_version, first_version);
+
+ /* Patch up the 'handle_ri_rdhwr_vivt' handler. */
+ vivt_exc = (unsigned long *) &handle_ri_rdhwr_vivt;
+ vivt_exc++;
+ *vivt_exc = (*vivt_exc & ~mask) | mask;
+
+ current_cpu_data.asid_cache = first_version;
+}
+
static int check_for_high_segbits __cpuinitdata;
static unsigned int kscratch_used_mask __cpuinitdata;
@@ -2162,6 +2205,7 @@ void __cpuinit build_tlb_refill_handler(void)
case CPU_TX3922:
case CPU_TX3927:
#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
+ setup_asid(0x40, 0xfc0, 0xf000, ASID_FIRST_VERSION_R3000);
build_r3000_tlb_refill_handler();
if (!run_once) {
build_r3000_tlb_load_handler();
@@ -2184,6 +2228,11 @@ void __cpuinit build_tlb_refill_handler(void)
break;
default:
+#ifndef CONFIG_MIPS_MT_SMTC
+ setup_asid(0x1, 0xff, 0xff00, ASID_FIRST_VERSION_R4000);
+#else
+ setup_asid(0x1, smtc_asid_mask, 0xff00, ASID_FIRST_VERSION_R4000);
+#endif
if (!run_once) {
scratch_reg = allocate_kscratch();
#ifdef CONFIG_MIPS_PGD_C0_CONTEXT