[ARM] mm 3: separate out supersection mappings, avoid for <4GB
Catalin Marinas at ARM Ltd says:
> The CPU architects in ARM intended supersections only as a way to map
> addresses >= 4GB. Supersections are not mandated by the architecture
> and there is no easy way to detect their hardware support at run-time
> (other than checking for a specific core). From the analysis done in
> ARM, there wasn't a clear performance gain by using supersections
> rather than sections (no significant improvement in the TLB misses).
Therefore, we should avoid using supersections unless there's a real
need (iow, we're mapping addresses >= 4GB).
This means that we can simplify create_mapping() a bit since we will
only use supersection mappings for addresses >= 4GB, which means that
the physical, virtual and length must be multiples of the supersection
mapping size.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index 0ac615c..800855b 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -302,7 +302,7 @@
#ifndef CONFIG_SMP
if (DOMAIN_IO == 0 &&
(((cpu_architecture() >= CPU_ARCH_ARMv6) && (get_cr() & CR_XP)) ||
- cpu_is_xsc3()) &&
+ cpu_is_xsc3()) && pfn >= 0x100000 &&
!((__pfn_to_phys(pfn) | size | addr) & ~SUPERSECTION_MASK)) {
area->flags |= VM_ARM_SECTION_MAPPING;
err = remap_area_supersections(addr, pfn, size, flags);
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index e359f36..3213980 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -398,21 +398,6 @@
}
/*
- * Create a SUPER SECTION PGD between VIRT and PHYS with protection PROT
- */
-static inline void
-alloc_init_supersection(unsigned long virt, unsigned long phys, int prot)
-{
- int i;
-
- for (i = 0; i < 16; i += 1) {
- alloc_init_section(virt, phys, prot | PMD_SECT_SUPER);
-
- virt += (PGDIR_SIZE / 2);
- }
-}
-
-/*
* Add a PAGE mapping between VIRT and PHYS in domain
* DOMAIN with protection PROT. Note that due to the
* way we map the PTEs, we must allocate two PTE_SIZE'd
@@ -436,6 +421,64 @@
set_pte_ext(ptep, pfn_pte(phys >> PAGE_SHIFT, __pgprot(type->prot_pte)), 0);
}
+static void __init create_36bit_mapping(struct map_desc *md,
+ const struct mem_type *type)
+{
+ unsigned long phys, addr, length, end;
+ pgd_t *pgd;
+
+ addr = md->virtual;
+ phys = (unsigned long)__pfn_to_phys(md->pfn);
+ length = PAGE_ALIGN(md->length);
+
+ if (!(cpu_architecture() >= CPU_ARCH_ARMv6 || cpu_is_xsc3())) {
+ printk(KERN_ERR "MM: CPU does not support supersection "
+ "mapping for 0x%08llx at 0x%08lx\n",
+ __pfn_to_phys((u64)md->pfn), addr);
+ return;
+ }
+
+ /* N.B. ARMv6 supersections are only defined to work with domain 0.
+ * Since domain assignments can in fact be arbitrary, the
+ * 'domain == 0' check below is required to insure that ARMv6
+ * supersections are only allocated for domain 0 regardless
+ * of the actual domain assignments in use.
+ */
+ if (type->domain) {
+ printk(KERN_ERR "MM: invalid domain in supersection "
+ "mapping for 0x%08llx at 0x%08lx\n",
+ __pfn_to_phys((u64)md->pfn), addr);
+ return;
+ }
+
+ if ((addr | length | __pfn_to_phys(md->pfn)) & ~SUPERSECTION_MASK) {
+ printk(KERN_ERR "MM: cannot create mapping for "
+ "0x%08llx at 0x%08lx invalid alignment\n",
+ __pfn_to_phys((u64)md->pfn), addr);
+ return;
+ }
+
+ /*
+ * Shift bits [35:32] of address into bits [23:20] of PMD
+ * (See ARMv6 spec).
+ */
+ phys |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20);
+
+ pgd = pgd_offset_k(addr);
+ end = addr + length;
+ do {
+ pmd_t *pmd = pmd_offset(pgd, addr);
+ int i;
+
+ for (i = 0; i < 16; i++)
+ *pmd++ = __pmd(phys | type->prot_sect | PMD_SECT_SUPER);
+
+ addr += SUPERSECTION_SIZE;
+ phys += SUPERSECTION_SIZE;
+ pgd += SUPERSECTION_SIZE >> PGDIR_SHIFT;
+ } while (addr != end);
+}
+
/*
* Create the page directory entries and any necessary
* page tables for the mapping specified by `md'. We
@@ -468,26 +511,9 @@
/*
* Catch 36-bit addresses
*/
- if(md->pfn >= 0x100000) {
- if (type->domain) {
- printk(KERN_ERR "MM: invalid domain in supersection "
- "mapping for 0x%08llx at 0x%08lx\n",
- __pfn_to_phys((u64)md->pfn), md->virtual);
- return;
- }
- if((md->virtual | md->length | __pfn_to_phys(md->pfn))
- & ~SUPERSECTION_MASK) {
- printk(KERN_ERR "MM: cannot create mapping for "
- "0x%08llx at 0x%08lx invalid alignment\n",
- __pfn_to_phys((u64)md->pfn), md->virtual);
- return;
- }
-
- /*
- * Shift bits [35:32] of address into bits [23:20] of PMD
- * (See ARMv6 spec).
- */
- off |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20);
+ if (md->pfn >= 0x100000) {
+ create_36bit_mapping(md, type);
+ return;
}
virt = md->virtual;
@@ -509,40 +535,6 @@
length -= PAGE_SIZE;
}
- /* N.B. ARMv6 supersections are only defined to work with domain 0.
- * Since domain assignments can in fact be arbitrary, the
- * 'domain == 0' check below is required to insure that ARMv6
- * supersections are only allocated for domain 0 regardless
- * of the actual domain assignments in use.
- */
- if ((cpu_architecture() >= CPU_ARCH_ARMv6 || cpu_is_xsc3())
- && type->domain == 0) {
- /*
- * Align to supersection boundary if !high pages.
- * High pages have already been checked for proper
- * alignment above and they will fail the SUPSERSECTION_MASK
- * check because of the way the address is encoded into
- * offset.
- */
- if (md->pfn <= 0x100000) {
- while ((virt & ~SUPERSECTION_MASK ||
- (virt + off) & ~SUPERSECTION_MASK) &&
- length >= (PGDIR_SIZE / 2)) {
- alloc_init_section(virt, virt + off, type->prot_sect);
-
- virt += (PGDIR_SIZE / 2);
- length -= (PGDIR_SIZE / 2);
- }
- }
-
- while (length >= SUPERSECTION_SIZE) {
- alloc_init_supersection(virt, virt + off, type->prot_sect);
-
- virt += SUPERSECTION_SIZE;
- length -= SUPERSECTION_SIZE;
- }
- }
-
/*
* A section mapping covers half a "pgdir" entry.
*/