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Some POWER5+ machines can do 64k hardware pages for normal memory but not for cache-inhibited pages. This patch lets us use 64k hardware pages for most user processes on such machines (assuming the kernel has been configured with CONFIG_PPC_64K_PAGES=y). User processes start out using 64k pages and get switched to 4k pages if they use any non-cacheable mappings. With this, we use 64k pages for the vmalloc region and 4k pages for the imalloc region. If anything creates a non-cacheable mapping in the vmalloc region, the vmalloc region will get switched to 4k pages. I don't know of any driver other than the DRM that would do this, though, and these machines don't have AGP. When a region gets switched from 64k pages to 4k pages, we do not have to clear out all the 64k HPTEs from the hash table immediately. We use the _PAGE_COMBO bit in the Linux PTE to indicate whether the page was hashed in as a 64k page or a set of 4k pages. If hash_page is trying to insert a 4k page for a Linux PTE and it sees that it has already been inserted as a 64k page, it first invalidates the 64k HPTE before inserting the 4k HPTE. The hash invalidation routines also use the _PAGE_COMBO bit, to determine whether to look for a 64k HPTE or a set of 4k HPTEs to remove. With those two changes, we can tolerate a mix of 4k and 64k HPTEs in the hash table, and they will all get removed when the address space is torn down. Signed-off-by: Paul Mackerras <paulus@samba.org>
67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
/*
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* MMU context allocation for 64-bit kernels.
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*
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* Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <linux/config.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/spinlock.h>
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#include <linux/idr.h>
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#include <asm/mmu_context.h>
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static DEFINE_SPINLOCK(mmu_context_lock);
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static DEFINE_IDR(mmu_context_idr);
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int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
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{
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int index;
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int err;
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again:
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if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL))
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return -ENOMEM;
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spin_lock(&mmu_context_lock);
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err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
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spin_unlock(&mmu_context_lock);
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if (err == -EAGAIN)
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goto again;
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else if (err)
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return err;
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if (index > MAX_CONTEXT) {
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idr_remove(&mmu_context_idr, index);
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return -ENOMEM;
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}
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mm->context.id = index;
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mm->context.user_psize = mmu_virtual_psize;
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mm->context.sllp = SLB_VSID_USER |
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mmu_psize_defs[mmu_virtual_psize].sllp;
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return 0;
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}
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void destroy_context(struct mm_struct *mm)
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{
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spin_lock(&mmu_context_lock);
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idr_remove(&mmu_context_idr, mm->context.id);
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spin_unlock(&mmu_context_lock);
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mm->context.id = NO_CONTEXT;
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}
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