/*
- * linux/arch/i386/mm/init.c
*
* Copyright (C) 1995 Linus Torvalds
*
unsigned int __VMALLOC_RESERVE = 128 << 20;
+unsigned long max_pfn_mapped;
+
DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
unsigned long highstart_pfn, highend_pfn;
/*
* Map with big pages if possible, otherwise
* create normal page tables:
+ *
+ * Don't use a large page for the first 2/4MB of memory
+ * because there are often fixed size MTRRs in there
+ * and overlapping MTRRs into large pages can cause
+ * slowdowns.
*/
- if (cpu_has_pse) {
+ if (cpu_has_pse && !(pgd_idx == 0 && pmd_idx == 0)) {
unsigned int addr2;
pgprot_t prot = PAGE_KERNEL_LARGE;
set_pmd(pmd, pfn_pmd(pfn, prot));
pfn += PTRS_PER_PTE;
+ max_pfn_mapped = pfn;
continue;
}
pte = one_page_table_init(pmd);
set_pte(pte, pfn_pte(pfn, prot));
}
+ max_pfn_mapped = pfn;
}
}
}
return 0;
}
+/*
+ * devmem_is_allowed() checks to see if /dev/mem access to a certain address
+ * is valid. The argument is a physical page number.
+ *
+ *
+ * On x86, access has to be given to the first megabyte of ram because that area
+ * contains bios code and data regions used by X and dosemu and similar apps.
+ * Access has to be given to non-kernel-ram areas as well, these contain the PCI
+ * mmio resources as well as potential bios/acpi data regions.
+ */
+int devmem_is_allowed(unsigned long pagenr)
+{
+ if (pagenr <= 256)
+ return 1;
+ if (!page_is_ram(pagenr))
+ return 1;
+ return 0;
+}
+
#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
pgprot_t kmap_prot;