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authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/arch/cris/arch-v10/mm
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/arch/cris/arch-v10/mm')
-rw-r--r--kernel/arch/cris/arch-v10/mm/Makefile6
-rw-r--r--kernel/arch/cris/arch-v10/mm/fault.c95
-rw-r--r--kernel/arch/cris/arch-v10/mm/init.c263
-rw-r--r--kernel/arch/cris/arch-v10/mm/tlb.c176
4 files changed, 540 insertions, 0 deletions
diff --git a/kernel/arch/cris/arch-v10/mm/Makefile b/kernel/arch/cris/arch-v10/mm/Makefile
new file mode 100644
index 000000000..588b4baee
--- /dev/null
+++ b/kernel/arch/cris/arch-v10/mm/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for the linux cris-specific parts of the memory manager.
+#
+
+obj-y := fault.o init.o tlb.o
+
diff --git a/kernel/arch/cris/arch-v10/mm/fault.c b/kernel/arch/cris/arch-v10/mm/fault.c
new file mode 100644
index 000000000..ed60588f8
--- /dev/null
+++ b/kernel/arch/cris/arch-v10/mm/fault.c
@@ -0,0 +1,95 @@
+/*
+ * linux/arch/cris/mm/fault.c
+ *
+ * Low level bus fault handler
+ *
+ *
+ * Copyright (C) 2000-2007 Axis Communications AB
+ *
+ * Authors: Bjorn Wesen
+ *
+ */
+
+#include <linux/mm.h>
+#include <asm/uaccess.h>
+#include <asm/pgtable.h>
+#include <arch/svinto.h>
+#include <asm/mmu_context.h>
+
+/* debug of low-level TLB reload */
+#undef DEBUG
+
+#ifdef DEBUG
+#define D(x) x
+#else
+#define D(x)
+#endif
+
+extern const struct exception_table_entry
+ *search_exception_tables(unsigned long addr);
+
+asmlinkage void do_page_fault(unsigned long address, struct pt_regs *regs,
+ int protection, int writeaccess);
+
+/* fast TLB-fill fault handler
+ * this is called from entry.S with interrupts disabled
+ */
+
+void
+handle_mmu_bus_fault(struct pt_regs *regs)
+{
+ int cause;
+ int select;
+#ifdef DEBUG
+ int index;
+ int page_id;
+ int acc, inv;
+#endif
+ pgd_t* pgd = (pgd_t*)per_cpu(current_pgd, smp_processor_id());
+ pmd_t *pmd;
+ pte_t pte;
+ int miss, we, writeac;
+ unsigned long address;
+ unsigned long flags;
+
+ cause = *R_MMU_CAUSE;
+
+ address = cause & PAGE_MASK; /* get faulting address */
+ select = *R_TLB_SELECT;
+
+#ifdef DEBUG
+ page_id = IO_EXTRACT(R_MMU_CAUSE, page_id, cause);
+ acc = IO_EXTRACT(R_MMU_CAUSE, acc_excp, cause);
+ inv = IO_EXTRACT(R_MMU_CAUSE, inv_excp, cause);
+ index = IO_EXTRACT(R_TLB_SELECT, index, select);
+#endif
+ miss = IO_EXTRACT(R_MMU_CAUSE, miss_excp, cause);
+ we = IO_EXTRACT(R_MMU_CAUSE, we_excp, cause);
+ writeac = IO_EXTRACT(R_MMU_CAUSE, wr_rd, cause);
+
+ D(printk("bus_fault from IRP 0x%lx: addr 0x%lx, miss %d, inv %d, we %d, acc %d, dx %d pid %d\n",
+ regs->irp, address, miss, inv, we, acc, index, page_id));
+
+ /* leave it to the MM system fault handler */
+ if (miss)
+ do_page_fault(address, regs, 0, writeac);
+ else
+ do_page_fault(address, regs, 1, we);
+
+ /* Reload TLB with new entry to avoid an extra miss exception.
+ * do_page_fault may have flushed the TLB so we have to restore
+ * the MMU registers.
+ */
+ local_irq_save(flags);
+ pmd = (pmd_t *)(pgd + pgd_index(address));
+ if (pmd_none(*pmd))
+ goto exit;
+ pte = *pte_offset_kernel(pmd, address);
+ if (!pte_present(pte))
+ goto exit;
+ *R_TLB_SELECT = select;
+ *R_TLB_HI = cause;
+ *R_TLB_LO = pte_val(pte);
+exit:
+ local_irq_restore(flags);
+}
diff --git a/kernel/arch/cris/arch-v10/mm/init.c b/kernel/arch/cris/arch-v10/mm/init.c
new file mode 100644
index 000000000..e7f806610
--- /dev/null
+++ b/kernel/arch/cris/arch-v10/mm/init.c
@@ -0,0 +1,263 @@
+/*
+ * linux/arch/cris/arch-v10/mm/init.c
+ *
+ */
+#include <linux/mmzone.h>
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/mm.h>
+#include <asm/pgtable.h>
+#include <asm/page.h>
+#include <asm/types.h>
+#include <asm/mmu.h>
+#include <asm/io.h>
+#include <asm/mmu_context.h>
+#include <arch/svinto.h>
+
+extern void tlb_init(void);
+
+/*
+ * The kernel is already mapped with a kernel segment at kseg_c so
+ * we don't need to map it with a page table. However head.S also
+ * temporarily mapped it at kseg_4 so we should set up the ksegs again,
+ * clear the TLB and do some other paging setup stuff.
+ */
+
+void __init
+paging_init(void)
+{
+ int i;
+ unsigned long zones_size[MAX_NR_ZONES];
+
+ printk("Setting up paging and the MMU.\n");
+
+ /* clear out the init_mm.pgd that will contain the kernel's mappings */
+
+ for(i = 0; i < PTRS_PER_PGD; i++)
+ swapper_pg_dir[i] = __pgd(0);
+
+ /* make sure the current pgd table points to something sane
+ * (even if it is most probably not used until the next
+ * switch_mm)
+ */
+
+ per_cpu(current_pgd, smp_processor_id()) = init_mm.pgd;
+
+ /* initialise the TLB (tlb.c) */
+
+ tlb_init();
+
+ /* see README.mm for details on the KSEG setup */
+
+#ifdef CONFIG_CRIS_LOW_MAP
+ /* Etrax-100 LX version 1 has a bug so that we cannot map anything
+ * across the 0x80000000 boundary, so we need to shrink the user-virtual
+ * area to 0x50000000 instead of 0xb0000000 and map things slightly
+ * different. The unused areas are marked as paged so that we can catch
+ * freak kernel accesses there.
+ *
+ * The ARTPEC chip is mapped at 0xa so we pass that segment straight
+ * through. We cannot vremap it because the vmalloc area is below 0x8
+ * and Juliette needs an uncached area above 0x8.
+ *
+ * Same thing with 0xc and 0x9, which is memory-mapped I/O on some boards.
+ * We map them straight over in LOW_MAP, but use vremap in LX version 2.
+ */
+
+#define CACHED_BOOTROM (KSEG_F | 0x08000000UL)
+
+ *R_MMU_KSEG = ( IO_STATE(R_MMU_KSEG, seg_f, seg ) | /* bootrom */
+ IO_STATE(R_MMU_KSEG, seg_e, page ) |
+ IO_STATE(R_MMU_KSEG, seg_d, page ) |
+ IO_STATE(R_MMU_KSEG, seg_c, page ) |
+ IO_STATE(R_MMU_KSEG, seg_b, seg ) | /* kernel reg area */
+#ifdef CONFIG_JULIETTE
+ IO_STATE(R_MMU_KSEG, seg_a, seg ) | /* ARTPEC etc. */
+#else
+ IO_STATE(R_MMU_KSEG, seg_a, page ) |
+#endif
+ IO_STATE(R_MMU_KSEG, seg_9, seg ) | /* LED's on some boards */
+ IO_STATE(R_MMU_KSEG, seg_8, seg ) | /* CSE0/1, flash and I/O */
+ IO_STATE(R_MMU_KSEG, seg_7, page ) | /* kernel vmalloc area */
+ IO_STATE(R_MMU_KSEG, seg_6, seg ) | /* kernel DRAM area */
+ IO_STATE(R_MMU_KSEG, seg_5, seg ) | /* cached flash */
+ IO_STATE(R_MMU_KSEG, seg_4, page ) | /* user area */
+ IO_STATE(R_MMU_KSEG, seg_3, page ) | /* user area */
+ IO_STATE(R_MMU_KSEG, seg_2, page ) | /* user area */
+ IO_STATE(R_MMU_KSEG, seg_1, page ) | /* user area */
+ IO_STATE(R_MMU_KSEG, seg_0, page ) ); /* user area */
+
+ *R_MMU_KBASE_HI = ( IO_FIELD(R_MMU_KBASE_HI, base_f, 0x3 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_e, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_d, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_c, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_b, 0xb ) |
+#ifdef CONFIG_JULIETTE
+ IO_FIELD(R_MMU_KBASE_HI, base_a, 0xa ) |
+#else
+ IO_FIELD(R_MMU_KBASE_HI, base_a, 0x0 ) |
+#endif
+ IO_FIELD(R_MMU_KBASE_HI, base_9, 0x9 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_8, 0x8 ) );
+
+ *R_MMU_KBASE_LO = ( IO_FIELD(R_MMU_KBASE_LO, base_7, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_6, 0x4 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_5, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_4, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_3, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_2, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_1, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_0, 0x0 ) );
+#else
+ /* This code is for the corrected Etrax-100 LX version 2... */
+
+#define CACHED_BOOTROM (KSEG_A | 0x08000000UL)
+
+ *R_MMU_KSEG = ( IO_STATE(R_MMU_KSEG, seg_f, seg ) | /* cached flash */
+ IO_STATE(R_MMU_KSEG, seg_e, seg ) | /* uncached flash */
+ IO_STATE(R_MMU_KSEG, seg_d, page ) | /* vmalloc area */
+ IO_STATE(R_MMU_KSEG, seg_c, seg ) | /* kernel area */
+ IO_STATE(R_MMU_KSEG, seg_b, seg ) | /* kernel reg area */
+ IO_STATE(R_MMU_KSEG, seg_a, seg ) | /* bootrom */
+ IO_STATE(R_MMU_KSEG, seg_9, page ) | /* user area */
+ IO_STATE(R_MMU_KSEG, seg_8, page ) |
+ IO_STATE(R_MMU_KSEG, seg_7, page ) |
+ IO_STATE(R_MMU_KSEG, seg_6, page ) |
+ IO_STATE(R_MMU_KSEG, seg_5, page ) |
+ IO_STATE(R_MMU_KSEG, seg_4, page ) |
+ IO_STATE(R_MMU_KSEG, seg_3, page ) |
+ IO_STATE(R_MMU_KSEG, seg_2, page ) |
+ IO_STATE(R_MMU_KSEG, seg_1, page ) |
+ IO_STATE(R_MMU_KSEG, seg_0, page ) );
+
+ *R_MMU_KBASE_HI = ( IO_FIELD(R_MMU_KBASE_HI, base_f, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_e, 0x8 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_d, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_c, 0x4 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_b, 0xb ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_a, 0x3 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_9, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_HI, base_8, 0x0 ) );
+
+ *R_MMU_KBASE_LO = ( IO_FIELD(R_MMU_KBASE_LO, base_7, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_6, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_5, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_4, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_3, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_2, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_1, 0x0 ) |
+ IO_FIELD(R_MMU_KBASE_LO, base_0, 0x0 ) );
+#endif
+
+ *R_MMU_CONTEXT = ( IO_FIELD(R_MMU_CONTEXT, page_id, 0 ) );
+
+ /* The MMU has been enabled ever since head.S but just to make
+ * it totally obvious we do it here as well.
+ */
+
+ *R_MMU_CTRL = ( IO_STATE(R_MMU_CTRL, inv_excp, enable ) |
+ IO_STATE(R_MMU_CTRL, acc_excp, enable ) |
+ IO_STATE(R_MMU_CTRL, we_excp, enable ) );
+
+ *R_MMU_ENABLE = IO_STATE(R_MMU_ENABLE, mmu_enable, enable);
+
+ /*
+ * initialize the bad page table and bad page to point
+ * to a couple of allocated pages
+ */
+
+ empty_zero_page = (unsigned long)alloc_bootmem_pages(PAGE_SIZE);
+ memset((void *)empty_zero_page, 0, PAGE_SIZE);
+
+ /* All pages are DMA'able in Etrax, so put all in the DMA'able zone */
+
+ zones_size[0] = ((unsigned long)high_memory - PAGE_OFFSET) >> PAGE_SHIFT;
+
+ for (i = 1; i < MAX_NR_ZONES; i++)
+ zones_size[i] = 0;
+
+ /* Use free_area_init_node instead of free_area_init, because the former
+ * is designed for systems where the DRAM starts at an address substantially
+ * higher than 0, like us (we start at PAGE_OFFSET). This saves space in the
+ * mem_map page array.
+ */
+
+ free_area_init_node(0, zones_size, PAGE_OFFSET >> PAGE_SHIFT, 0);
+}
+
+/* Initialize remaps of some I/O-ports. It is important that this
+ * is called before any driver is initialized.
+ */
+
+static int
+__init init_ioremap(void)
+{
+
+ /* Give the external I/O-port addresses their values */
+
+#ifdef CONFIG_CRIS_LOW_MAP
+ /* Simply a linear map (see the KSEG map above in paging_init) */
+ port_cse1_addr = (volatile unsigned long *)(MEM_CSE1_START |
+ MEM_NON_CACHEABLE);
+ port_csp0_addr = (volatile unsigned long *)(MEM_CSP0_START |
+ MEM_NON_CACHEABLE);
+ port_csp4_addr = (volatile unsigned long *)(MEM_CSP4_START |
+ MEM_NON_CACHEABLE);
+#else
+ /* Note that nothing blows up just because we do this remapping
+ * it's ok even if the ports are not used or connected
+ * to anything (or connected to a non-I/O thing) */
+ port_cse1_addr = (volatile unsigned long *)
+ ioremap((unsigned long)(MEM_CSE1_START | MEM_NON_CACHEABLE), 16);
+ port_csp0_addr = (volatile unsigned long *)
+ ioremap((unsigned long)(MEM_CSP0_START | MEM_NON_CACHEABLE), 16);
+ port_csp4_addr = (volatile unsigned long *)
+ ioremap((unsigned long)(MEM_CSP4_START | MEM_NON_CACHEABLE), 16);
+#endif
+ return 0;
+}
+
+__initcall(init_ioremap);
+
+/* Helper function for the two below */
+
+static inline void
+flush_etrax_cacherange(void *startadr, int length)
+{
+ /* CACHED_BOOTROM is mapped to the boot-rom area (cached) which
+ * we can use to get fast dummy-reads of cachelines
+ */
+
+ volatile short *flushadr = (volatile short *)(((unsigned long)startadr & ~PAGE_MASK) |
+ CACHED_BOOTROM);
+
+ length = length > 8192 ? 8192 : length; /* No need to flush more than cache size */
+
+ while(length > 0) {
+ *flushadr; /* dummy read to flush */
+ flushadr += (32/sizeof(short)); /* a cacheline is 32 bytes */
+ length -= 32;
+ }
+}
+
+/* Due to a bug in Etrax100(LX) all versions, receiving DMA buffers
+ * will occasionally corrupt certain CPU writes if the DMA buffers
+ * happen to be hot in the cache.
+ *
+ * As a workaround, we have to flush the relevant parts of the cache
+ * before (re) inserting any receiving descriptor into the DMA HW.
+ */
+
+void
+prepare_rx_descriptor(struct etrax_dma_descr *desc)
+{
+ flush_etrax_cacherange((void *)desc->buf, desc->sw_len ? desc->sw_len : 65536);
+}
+
+/* Do the same thing but flush the entire cache */
+
+void
+flush_etrax_cache(void)
+{
+ flush_etrax_cacherange(0, 8192);
+}
diff --git a/kernel/arch/cris/arch-v10/mm/tlb.c b/kernel/arch/cris/arch-v10/mm/tlb.c
new file mode 100644
index 000000000..21d78c599
--- /dev/null
+++ b/kernel/arch/cris/arch-v10/mm/tlb.c
@@ -0,0 +1,176 @@
+/*
+ * linux/arch/cris/arch-v10/mm/tlb.c
+ *
+ * Low level TLB handling
+ *
+ *
+ * Copyright (C) 2000-2007 Axis Communications AB
+ *
+ * Authors: Bjorn Wesen (bjornw@axis.com)
+ *
+ */
+
+#include <asm/tlb.h>
+#include <asm/mmu_context.h>
+#include <arch/svinto.h>
+
+#define D(x)
+
+/* The TLB can host up to 64 different mm contexts at the same time.
+ * The running context is R_MMU_CONTEXT, and each TLB entry contains a
+ * page_id that has to match to give a hit. In page_id_map, we keep track
+ * of which mm's we have assigned which page_id's, so that we know when
+ * to invalidate TLB entries.
+ *
+ * The last page_id is never running - it is used as an invalid page_id
+ * so we can make TLB entries that will never match.
+ *
+ * Notice that we need to make the flushes atomic, otherwise an interrupt
+ * handler that uses vmalloced memory might cause a TLB load in the middle
+ * of a flush causing.
+ */
+
+/* invalidate all TLB entries */
+
+void
+flush_tlb_all(void)
+{
+ int i;
+ unsigned long flags;
+
+ /* the vpn of i & 0xf is so we dont write similar TLB entries
+ * in the same 4-way entry group. details...
+ */
+
+ local_irq_save(flags);
+ for(i = 0; i < NUM_TLB_ENTRIES; i++) {
+ *R_TLB_SELECT = ( IO_FIELD(R_TLB_SELECT, index, i) );
+ *R_TLB_HI = ( IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
+ IO_FIELD(R_TLB_HI, vpn, i & 0xf ) );
+
+ *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no ) |
+ IO_STATE(R_TLB_LO, valid, no ) |
+ IO_STATE(R_TLB_LO, kernel,no ) |
+ IO_STATE(R_TLB_LO, we, no ) |
+ IO_FIELD(R_TLB_LO, pfn, 0 ) );
+ }
+ local_irq_restore(flags);
+ D(printk("tlb: flushed all\n"));
+}
+
+/* invalidate the selected mm context only */
+
+void
+flush_tlb_mm(struct mm_struct *mm)
+{
+ int i;
+ int page_id = mm->context.page_id;
+ unsigned long flags;
+
+ D(printk("tlb: flush mm context %d (%p)\n", page_id, mm));
+
+ if(page_id == NO_CONTEXT)
+ return;
+
+ /* mark the TLB entries that match the page_id as invalid.
+ * here we could also check the _PAGE_GLOBAL bit and NOT flush
+ * global pages. is it worth the extra I/O ?
+ */
+
+ local_irq_save(flags);
+ for(i = 0; i < NUM_TLB_ENTRIES; i++) {
+ *R_TLB_SELECT = IO_FIELD(R_TLB_SELECT, index, i);
+ if (IO_EXTRACT(R_TLB_HI, page_id, *R_TLB_HI) == page_id) {
+ *R_TLB_HI = ( IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
+ IO_FIELD(R_TLB_HI, vpn, i & 0xf ) );
+
+ *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no ) |
+ IO_STATE(R_TLB_LO, valid, no ) |
+ IO_STATE(R_TLB_LO, kernel,no ) |
+ IO_STATE(R_TLB_LO, we, no ) |
+ IO_FIELD(R_TLB_LO, pfn, 0 ) );
+ }
+ }
+ local_irq_restore(flags);
+}
+
+/* invalidate a single page */
+
+void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ int page_id = mm->context.page_id;
+ int i;
+ unsigned long flags;
+
+ D(printk("tlb: flush page %p in context %d (%p)\n", addr, page_id, mm));
+
+ if(page_id == NO_CONTEXT)
+ return;
+
+ addr &= PAGE_MASK; /* perhaps not necessary */
+
+ /* invalidate those TLB entries that match both the mm context
+ * and the virtual address requested
+ */
+
+ local_irq_save(flags);
+ for(i = 0; i < NUM_TLB_ENTRIES; i++) {
+ unsigned long tlb_hi;
+ *R_TLB_SELECT = IO_FIELD(R_TLB_SELECT, index, i);
+ tlb_hi = *R_TLB_HI;
+ if (IO_EXTRACT(R_TLB_HI, page_id, tlb_hi) == page_id &&
+ (tlb_hi & PAGE_MASK) == addr) {
+ *R_TLB_HI = IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
+ addr; /* same addr as before works. */
+
+ *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no ) |
+ IO_STATE(R_TLB_LO, valid, no ) |
+ IO_STATE(R_TLB_LO, kernel,no ) |
+ IO_STATE(R_TLB_LO, we, no ) |
+ IO_FIELD(R_TLB_LO, pfn, 0 ) );
+ }
+ }
+ local_irq_restore(flags);
+}
+
+/*
+ * Initialize the context related info for a new mm_struct
+ * instance.
+ */
+
+int
+init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+ mm->context.page_id = NO_CONTEXT;
+ return 0;
+}
+
+/* called in schedule() just before actually doing the switch_to */
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+ struct task_struct *tsk)
+{
+ if (prev != next) {
+ /* make sure we have a context */
+ get_mmu_context(next);
+
+ /* remember the pgd for the fault handlers
+ * this is similar to the pgd register in some other CPU's.
+ * we need our own copy of it because current and active_mm
+ * might be invalid at points where we still need to derefer
+ * the pgd.
+ */
+
+ per_cpu(current_pgd, smp_processor_id()) = next->pgd;
+
+ /* switch context in the MMU */
+
+ D(printk(KERN_DEBUG "switching mmu_context to %d (%p)\n",
+ next->context, next));
+
+ *R_MMU_CONTEXT = IO_FIELD(R_MMU_CONTEXT,
+ page_id, next->context.page_id);
+ }
+}
+