powerpc: Use 64k pages without needing cache-inhibited large pages
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>
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index b43ed92e..d03fd2b 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -92,10 +92,15 @@
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 @@
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 @@
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 @@
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 @@
#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 @@
#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);