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powerpc: Use 64k pages without needing cache-inhibited large pages

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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>
This commit is contained in:
Paul Mackerras
2006-06-15 10:45:18 +10:00
parent 31925323b1
commit bf72aeba2f
13 changed files with 160 additions and 39 deletions
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84
arch/powerpc/mm/hash_utils_64.c
View File

@@ -92,10 +92,15 @@ unsigned long htab_size_bytes;
unsigned long htab_hash_mask;
int mmu_linear_psize = MMU_PAGE_4K;
int mmu_virtual_psize = MMU_PAGE_4K;
int mmu_vmalloc_psize = MMU_PAGE_4K;
int mmu_io_psize = MMU_PAGE_4K;
#ifdef CONFIG_HUGETLB_PAGE
int mmu_huge_psize = MMU_PAGE_16M;
unsigned int HPAGE_SHIFT;
#endif
#ifdef CONFIG_PPC_64K_PAGES
int mmu_ci_restrictions;
#endif
/* There are definitions of page sizes arrays to be used when none
* is provided by the firmware.
@@ -308,20 +313,31 @@ static void __init htab_init_page_sizes(void)
else if (mmu_psize_defs[MMU_PAGE_1M].shift)
mmu_linear_psize = MMU_PAGE_1M;
#ifdef CONFIG_PPC_64K_PAGES
/*
* Pick a size for the ordinary pages. Default is 4K, we support
* 64K if cache inhibited large pages are supported by the
* processor
* 64K for user mappings and vmalloc if supported by the processor.
* We only use 64k for ioremap if the processor
* (and firmware) support cache-inhibited large pages.
* If not, we use 4k and set mmu_ci_restrictions so that
* hash_page knows to switch processes that use cache-inhibited
* mappings to 4k pages.
*/
#ifdef CONFIG_PPC_64K_PAGES
if (mmu_psize_defs[MMU_PAGE_64K].shift &&
cpu_has_feature(CPU_FTR_CI_LARGE_PAGE))
if (mmu_psize_defs[MMU_PAGE_64K].shift) {
mmu_virtual_psize = MMU_PAGE_64K;
mmu_vmalloc_psize = MMU_PAGE_64K;
if (cpu_has_feature(CPU_FTR_CI_LARGE_PAGE))
mmu_io_psize = MMU_PAGE_64K;
else
mmu_ci_restrictions = 1;
}
#endif
printk(KERN_DEBUG "Page orders: linear mapping = %d, others = %d\n",
printk(KERN_DEBUG "Page orders: linear mapping = %d, "
"virtual = %d, io = %d\n",
mmu_psize_defs[mmu_linear_psize].shift,
mmu_psize_defs[mmu_virtual_psize].shift);
mmu_psize_defs[mmu_virtual_psize].shift,
mmu_psize_defs[mmu_io_psize].shift);
#ifdef CONFIG_HUGETLB_PAGE
/* Init large page size. Currently, we pick 16M or 1M depending
@@ -556,6 +572,7 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
pte_t *ptep;
cpumask_t tmp;
int rc, user_region = 0, local = 0;
int psize;
DBG_LOW("hash_page(ea=%016lx, access=%lx, trap=%lx\n",
ea, access, trap);
@@ -575,10 +592,15 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
return 1;
}
vsid = get_vsid(mm->context.id, ea);
psize = mm->context.user_psize;
break;
case VMALLOC_REGION_ID:
mm = &init_mm;
vsid = get_kernel_vsid(ea);
if (ea < VMALLOC_END)
psize = mmu_vmalloc_psize;
else
psize = mmu_io_psize;
break;
default:
/* Not a valid range
@@ -629,7 +651,40 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
#ifndef CONFIG_PPC_64K_PAGES
rc = __hash_page_4K(ea, access, vsid, ptep, trap, local);
#else
if (mmu_virtual_psize == MMU_PAGE_64K)
if (mmu_ci_restrictions) {
/* If this PTE is non-cacheable, switch to 4k */
if (psize == MMU_PAGE_64K &&
(pte_val(*ptep) & _PAGE_NO_CACHE)) {
if (user_region) {
psize = MMU_PAGE_4K;
mm->context.user_psize = MMU_PAGE_4K;
mm->context.sllp = SLB_VSID_USER |
mmu_psize_defs[MMU_PAGE_4K].sllp;
} else if (ea < VMALLOC_END) {
/*
* some driver did a non-cacheable mapping
* in vmalloc space, so switch vmalloc
* to 4k pages
*/
printk(KERN_ALERT "Reducing vmalloc segment "
"to 4kB pages because of "
"non-cacheable mapping\n");
psize = mmu_vmalloc_psize = MMU_PAGE_4K;
}
}
if (user_region) {
if (psize != get_paca()->context.user_psize) {
get_paca()->context = mm->context;
slb_flush_and_rebolt();
}
} else if (get_paca()->vmalloc_sllp !=
mmu_psize_defs[mmu_vmalloc_psize].sllp) {
get_paca()->vmalloc_sllp =
mmu_psize_defs[mmu_vmalloc_psize].sllp;
slb_flush_and_rebolt();
}
}
if (psize == MMU_PAGE_64K)
rc = __hash_page_64K(ea, access, vsid, ptep, trap, local);
else
rc = __hash_page_4K(ea, access, vsid, ptep, trap, local);
@@ -681,7 +736,18 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
#ifndef CONFIG_PPC_64K_PAGES
__hash_page_4K(ea, access, vsid, ptep, trap, local);
#else
if (mmu_virtual_psize == MMU_PAGE_64K)
if (mmu_ci_restrictions) {
/* If this PTE is non-cacheable, switch to 4k */
if (mm->context.user_psize == MMU_PAGE_64K &&
(pte_val(*ptep) & _PAGE_NO_CACHE)) {
mm->context.user_psize = MMU_PAGE_4K;
mm->context.sllp = SLB_VSID_USER |
mmu_psize_defs[MMU_PAGE_4K].sllp;
get_paca()->context = mm->context;
slb_flush_and_rebolt();
}
}
if (mm->context.user_psize == MMU_PAGE_64K)
__hash_page_64K(ea, access, vsid, ptep, trap, local);
else
__hash_page_4K(ea, access, vsid, ptep, trap, local);