x86, mm: Include the entire kernel memory map in trampoline_pgd

There are various pieces of code in arch/x86 that require a page table
with an identity mapping. Make trampoline_pgd a proper kernel page
table, it currently only includes the kernel text and module space
mapping.

One new feature of trampoline_pgd is that it now has mappings for the
physical I/O device addresses, which are inserted at ioremap()
time. Some broken implementations of EFI firmware require these
mappings to always be around.

Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

2 files changed, 113 insertions, 1 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 2b6b4a3c8beb..fd4404f19d39 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -108,13 +108,13 @@ void sync_global_pgds(unsigned long start, unsigned long end)
         for (address = start; address <= end; address += PGDIR_SIZE) {
                 const pgd_t *pgd_ref = pgd_offset_k(address);
                 struct page *page;
+                pgd_t *pgd;
 
                 if (pgd_none(*pgd_ref))
                         continue;
 
                 spin_lock(&pgd_lock);
                 list_for_each_entry(page, &pgd_list, lru) {
-                        pgd_t *pgd;
                         spinlock_t *pgt_lock;
 
                         pgd = (pgd_t *)page_address(page) + pgd_index(address);
@@ -130,6 +130,13 @@ void sync_global_pgds(unsigned long start, unsigned long end)
 
                         spin_unlock(pgt_lock);
                 }
+
+                pgd = __va(real_mode_header->trampoline_pgd);
+                pgd += pgd_index(address);
+
+                if (pgd_none(*pgd))
+                        set_pgd(pgd, *pgd_ref);
+
                 spin_unlock(&pgd_lock);
         }
 }
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 78fe3f1ac49f..e190f7b56653 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -50,6 +50,107 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
         return err;
 }
 
+#ifdef CONFIG_X86_64
+static void ident_pte_range(unsigned long paddr, unsigned long vaddr,
+                            pmd_t *ppmd, pmd_t *vpmd, unsigned long end)
+{
+        pte_t *ppte = pte_offset_kernel(ppmd, paddr);
+        pte_t *vpte = pte_offset_kernel(vpmd, vaddr);
+
+        do {
+                set_pte(ppte, *vpte);
+        } while (ppte++, vpte++, vaddr += PAGE_SIZE, vaddr != end);
+}
+
+static int ident_pmd_range(unsigned long paddr, unsigned long vaddr,
+                            pud_t *ppud, pud_t *vpud, unsigned long end)
+{
+        pmd_t *ppmd = pmd_offset(ppud, paddr);
+        pmd_t *vpmd = pmd_offset(vpud, vaddr);
+        unsigned long next;
+
+        do {
+                next = pmd_addr_end(vaddr, end);
+
+                if (!pmd_present(*ppmd)) {
+                        pte_t *ppte = (pte_t *)get_zeroed_page(GFP_KERNEL);
+                        if (!ppte)
+                                return 1;
+
+                        set_pmd(ppmd, __pmd(_KERNPG_TABLE | __pa(ppte)));
+                }
+
+                ident_pte_range(paddr, vaddr, ppmd, vpmd, next);
+        } while (ppmd++, vpmd++, vaddr = next, vaddr != end);
+
+        return 0;
+}
+
+static int ident_pud_range(unsigned long paddr, unsigned long vaddr,
+                            pgd_t *ppgd, pgd_t *vpgd, unsigned long end)
+{
+        pud_t *ppud = pud_offset(ppgd, paddr);
+        pud_t *vpud = pud_offset(vpgd, vaddr);
+        unsigned long next;
+
+        do {
+                next = pud_addr_end(vaddr, end);
+
+                if (!pud_present(*ppud)) {
+                        pmd_t *ppmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
+                        if (!ppmd)
+                                return 1;
+
+                        set_pud(ppud, __pud(_KERNPG_TABLE | __pa(ppmd)));
+                }
+
+                if (ident_pmd_range(paddr, vaddr, ppud, vpud, next))
+                        return 1;
+        } while (ppud++, vpud++, vaddr = next, vaddr != end);
+
+        return 0;
+}
+
+static int insert_identity_mapping(resource_size_t paddr, unsigned long vaddr,
+                                    unsigned long size)
+{
+        unsigned long end = vaddr + size;
+        unsigned long next;
+        pgd_t *vpgd, *ppgd;
+
+        /* Don't map over the guard hole. */
+        if (paddr >= 0x800000000000 || paddr + size > 0x800000000000)
+                return 1;
+
+        ppgd = __va(real_mode_header->trampoline_pgd) + pgd_index(paddr);
+
+        vpgd = pgd_offset_k(vaddr);
+        do {
+                next = pgd_addr_end(vaddr, end);
+
+                if (!pgd_present(*ppgd)) {
+                        pud_t *ppud = (pud_t *)get_zeroed_page(GFP_KERNEL);
+                        if (!ppud)
+                                return 1;
+
+                        set_pgd(ppgd, __pgd(_KERNPG_TABLE | __pa(ppud)));
+                }
+
+                if (ident_pud_range(paddr, vaddr, ppgd, vpgd, next))
+                        return 1;
+        } while (ppgd++, vpgd++, vaddr = next, vaddr != end);
+
+        return 0;
+}
+#else
+static inline int insert_identity_mapping(resource_size_t paddr,
+                                          unsigned long vaddr,
+                                          unsigned long size)
+{
+        return 0;
+}
+#endif /* CONFIG_X86_64 */
+
 /*
  * Remap an arbitrary physical address space into the kernel virtual
  * address space. Needed when the kernel wants to access high addresses
@@ -163,6 +264,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
         ret_addr = (void __iomem *) (vaddr + offset);
         mmiotrace_ioremap(unaligned_phys_addr, unaligned_size, ret_addr);
 
+        if (insert_identity_mapping(phys_addr, vaddr, size))
+                printk(KERN_WARNING "ioremap: unable to map 0x%llx in identity pagetable\n",
+                                        (unsigned long long)phys_addr);
+
         /*
          * Check if the request spans more than any BAR in the iomem resource
          * tree.