1 files changed, 131 insertions, 0 deletions
diff --git a/arch/tile/include/asm/mmu_context.h b/arch/tile/include/asm/mmu_context.h
new file mode 100644
index 000000000000..9bc0d0725c28
--- /dev/null
+++ b/arch/tile/include/asm/mmu_context.h
@@ -0,0 +1,131 @@
+/*
+ * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#ifndef _ASM_TILE_MMU_CONTEXT_H
+#define _ASM_TILE_MMU_CONTEXT_H
+
+#include <linux/smp.h>
+#include <asm/setup.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+#include <asm/homecache.h>
+#include <asm-generic/mm_hooks.h>
+
+static inline int
+init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+	return 0;
+}
+
+/* Note that arch/tile/kernel/head.S also calls hv_install_context() */
+static inline void __install_page_table(pgd_t *pgdir, int asid, pgprot_t prot)
+{
+	/* FIXME: DIRECTIO should not always be set. FIXME. */
+	int rc = hv_install_context(__pa(pgdir), prot, asid, HV_CTX_DIRECTIO);
+	if (rc < 0)
+		panic("hv_install_context failed: %d", rc);
+}
+
+static inline void install_page_table(pgd_t *pgdir, int asid)
+{
+	pte_t *ptep = virt_to_pte(NULL, (unsigned long)pgdir);
+	__install_page_table(pgdir, asid, *ptep);
+}
+
+/*
+ * "Lazy" TLB mode is entered when we are switching to a kernel task,
+ * which borrows the mm of the previous task.  The goal of this
+ * optimization is to avoid having to install a new page table.  On
+ * early x86 machines (where the concept originated) you couldn't do
+ * anything short of a full page table install for invalidation, so
+ * handling a remote TLB invalidate required doing a page table
+ * re-install.  Someone clearly decided that it was silly to keep
+ * doing this while in "lazy" TLB mode, so the optimization involves
+ * installing the swapper page table instead the first time one
+ * occurs, and clearing the cpu out of cpu_vm_mask, so the cpu running
+ * the kernel task doesn't need to take any more interrupts.  At that
+ * point it's then necessary to explicitly reinstall it when context
+ * switching back to the original mm.
+ *
+ * On Tile, we have to do a page-table install whenever DMA is enabled,
+ * so in that case lazy mode doesn't help anyway.  And more generally,
+ * we have efficient per-page TLB shootdown, and don't expect to spend
+ * that much time in kernel tasks in general, so just leaving the
+ * kernel task borrowing the old page table, but handling TLB
+ * shootdowns, is a reasonable thing to do.  And importantly, this
+ * lets us use the hypervisor's internal APIs for TLB shootdown, which
+ * means we don't have to worry about having TLB shootdowns blocked
+ * when Linux is disabling interrupts; see the page migration code for
+ * an example of where it's important for TLB shootdowns to complete
+ * even when interrupts are disabled at the Linux level.
+ */
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *t)
+{
+#if CHIP_HAS_TILE_DMA()
+	/*
+	 * We have to do an "identity" page table switch in order to
+	 * clear any pending DMA interrupts.
+	 */
+	if (current->thread.tile_dma_state.enabled)
+		install_page_table(mm->pgd, __get_cpu_var(current_asid));
+#endif
+}
+
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+			     struct task_struct *tsk)
+{
+	if (likely(prev != next)) {
+
+		int cpu = smp_processor_id();
+
+		/* Pick new ASID. */
+		int asid = __get_cpu_var(current_asid) + 1;
+		if (asid > max_asid) {
+			asid = min_asid;
+			local_flush_tlb();
+		}
+		__get_cpu_var(current_asid) = asid;
+
+		/* Clear cpu from the old mm, and set it in the new one. */
+		cpumask_clear_cpu(cpu, &prev->cpu_vm_mask);
+		cpumask_set_cpu(cpu, &next->cpu_vm_mask);
+
+		/* Re-load page tables */
+		install_page_table(next->pgd, asid);
+
+		/* See how we should set the red/black cache info */
+		check_mm_caching(prev, next);
+
+		/*
+		 * Since we're changing to a new mm, we have to flush
+		 * the icache in case some physical page now being mapped
+		 * has subsequently been repurposed and has new code.
+		 */
+		__flush_icache();
+
+	}
+}
+
+static inline void activate_mm(struct mm_struct *prev_mm,
+			       struct mm_struct *next_mm)
+{
+	switch_mm(prev_mm, next_mm, NULL);
+}
+
+#define destroy_context(mm)		do { } while (0)
+#define deactivate_mm(tsk, mm)          do { } while (0)
+
+#endif /* _ASM_TILE_MMU_CONTEXT_H */