x86: allow early use of fixmaps

As a prerequisite for adding an EHCI debug port based console
implementation, set up the page tables needed for (a sub-portion of)
the fixmaps together with other boot time page table construction.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -3,6 +3,7 @@
 #include <public/xen.h>
 #include <asm/asm_defns.h>
 #include <asm/desc.h>
+#include <asm/fixmap.h>
 #include <asm/page.h>
 #include <asm/msr.h>
 
@@ -121,6 +122,9 @@ __start:
         add     $8,%edx
         add     $(1<<L2_PAGETABLE_SHIFT),%eax
         loop    1b
+        /* Initialise L2 fixmap page directory entry. */
+        mov     $(sym_phys(l1_fixmap)+7),%eax
+        mov     %eax,sym_phys(l2_fixmap) + l2_table_offset(FIXADDR_TOP-1)*8
         /* Initialise L3 identity-map page directory entries. */
         mov     $sym_phys(l3_identmap),%edi
         mov     $(sym_phys(l2_identmap)+7),%eax
@@ -129,9 +133,11 @@ __start:
         add     $8,%edi
         add     $PAGE_SIZE,%eax
         loop    1b
-        /* Initialise L3 xen-map page directory entry. */
+        /* Initialise L3 xen-map and fixmap page directory entries. */
         mov     $(sym_phys(l2_xenmap)+7),%eax
         mov     %eax,sym_phys(l3_xenmap) + l3_table_offset(XEN_VIRT_START)*8
+        mov     $(sym_phys(l2_fixmap)+7),%eax
+        mov     %eax,sym_phys(l3_xenmap) + l3_table_offset(FIXADDR_TOP-1)*8
         /* Initialise L3 boot-map page directory entry. */
         mov     $(sym_phys(l2_bootmap)+7),%eax
         mov     %eax,sym_phys(l3_bootmap) + 0*8
@@ -157,6 +163,9 @@ __start:
         add     $(1<<L2_PAGETABLE_SHIFT),%eax
         cmp     $(16<<20)+0xe3,%eax
         jne     1b
+        /* Initialise L2 fixmap page directory entry. */
+        mov     $(sym_phys(l1_fixmap)+7),%eax
+        mov     %eax,sym_phys(idle_pg_table_l2) + l2_table_offset(FIXADDR_TOP-1)*8
 #endif
 
         /* Initialize 4kB mappings of first 2MB or 4MB of memory. */
--- a/xen/arch/x86/efi/boot.c
+++ b/xen/arch/x86/efi/boot.c
@@ -17,6 +17,9 @@
 #include <xen/vga.h>
 #include <asm/e820.h>
 #include <asm/edd.h>
+#define __ASSEMBLY__ /* avoid pulling in ACPI stuff (conflicts with EFI) */
+#include <asm/fixmap.h>
+#undef __ASSEMBLY__
 #include <asm/mm.h>
 #include <asm/msr.h>
 #include <asm/processor.h>
@@ -1123,14 +1126,19 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
         slot &= L2_PAGETABLE_ENTRIES - 1;
         l2_bootmap[slot] = l2e_from_paddr(addr, __PAGE_HYPERVISOR|_PAGE_PSE);
     }
+    /* Initialise L2 fixmap page directory entry. */
+    l2_fixmap[l2_table_offset(FIXADDR_TOP - 1)] =
+        l2e_from_paddr((UINTN)l1_fixmap, __PAGE_HYPERVISOR);
     /* Initialise L3 identity-map page directory entries. */
     for ( i = 0; i < ARRAY_SIZE(l2_identmap) / L2_PAGETABLE_ENTRIES; ++i )
         l3_identmap[i] = l3e_from_paddr((UINTN)(l2_identmap +
                                                 i * L2_PAGETABLE_ENTRIES),
                                         __PAGE_HYPERVISOR);
-    /* Initialise L3 xen-map page directory entry. */
+    /* Initialise L3 xen-map and fixmap page directory entries. */
     l3_xenmap[l3_table_offset(XEN_VIRT_START)] =
         l3e_from_paddr((UINTN)l2_xenmap, __PAGE_HYPERVISOR);
+    l3_xenmap[l3_table_offset(FIXADDR_TOP - 1)] =
+        l3e_from_paddr((UINTN)l2_fixmap, __PAGE_HYPERVISOR);
     /* Initialise L3 boot-map page directory entries. */
     l3_bootmap[l3_table_offset(xen_phys_start)] =
         l3e_from_paddr((UINTN)l2_bootmap, __PAGE_HYPERVISOR);
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -130,6 +130,10 @@
 l1_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
     l1_identmap[L1_PAGETABLE_ENTRIES];
 
+/* Mapping of the fixmap space needed early. */
+l1_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
+    l1_fixmap[L1_PAGETABLE_ENTRIES];
+
 #define MEM_LOG(_f, _a...) gdprintk(XENLOG_WARNING , _f "\n" , ## _a)
 
 /*
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -65,6 +65,10 @@ l3_pgentry_t __attribute__ ((__section__
 l2_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
     l2_xenmap[L2_PAGETABLE_ENTRIES];
 
+/* Enough page directories to map the early fixmap space. */
+l2_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
+    l2_fixmap[L2_PAGETABLE_ENTRIES];
+
 /* Enough page directories to map into the bottom 1GB. */
 l3_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
     l3_bootmap[L3_PAGETABLE_ENTRIES];
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -315,7 +315,11 @@ extern unsigned char boot_edid_info[128]
 #define MACHPHYS_MBYTES         16 /* 1 MB needed per 1 GB memory */
 #define FRAMETABLE_MBYTES       (MACHPHYS_MBYTES * 6)
 
+#ifndef __ASSEMBLY__
 #define IOREMAP_VIRT_END	0UL
+#else
+#define IOREMAP_VIRT_END	0
+#endif
 #define IOREMAP_VIRT_START	(IOREMAP_VIRT_END - (IOREMAP_MBYTES<<20))
 #define DIRECTMAP_VIRT_END	IOREMAP_VIRT_START
 #define DIRECTMAP_VIRT_START	(DIRECTMAP_VIRT_END - (DIRECTMAP_MBYTES<<20))
--- a/xen/include/asm-x86/fixmap.h
+++ b/xen/include/asm-x86/fixmap.h
@@ -13,12 +13,17 @@
 #define _ASM_FIXMAP_H
 
 #include <xen/config.h>
+#include <asm/page.h>
+
+#define FIXADDR_TOP (IOREMAP_VIRT_END - PAGE_SIZE)
+
+#ifndef __ASSEMBLY__
+
 #include <xen/pfn.h>
 #include <xen/kexec.h>
 #include <xen/iommu.h>
 #include <asm/apicdef.h>
 #include <asm/acpi.h>
-#include <asm/page.h>
 #include <asm/amd-iommu.h>
 #include <asm/msi.h>
 #include <acpi/apei.h>
@@ -66,7 +71,6 @@ enum fixed_addresses {
     __end_of_fixed_addresses
 };
 
-#define FIXADDR_TOP   (IOREMAP_VIRT_END - PAGE_SIZE)
 #define FIXADDR_SIZE  (__end_of_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
 
@@ -90,4 +94,6 @@ static inline unsigned long virt_to_fix(
     return __virt_to_fix(vaddr);
 }
 
+#endif /* __ASSEMBLY__ */
+
 #endif
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -306,13 +306,15 @@ extern l2_pgentry_t   idle_pg_table_l2[
 extern l2_pgentry_t  *compat_idle_pg_table_l2;
 extern unsigned int   m2p_compat_vstart;
 extern l2_pgentry_t l2_xenmap[L2_PAGETABLE_ENTRIES],
+    l2_fixmap[L2_PAGETABLE_ENTRIES],
     l2_bootmap[L2_PAGETABLE_ENTRIES];
 extern l3_pgentry_t l3_xenmap[L3_PAGETABLE_ENTRIES],
     l3_identmap[L3_PAGETABLE_ENTRIES],
     l3_bootmap[L3_PAGETABLE_ENTRIES];
 #endif
 extern l2_pgentry_t l2_identmap[4*L2_PAGETABLE_ENTRIES];
-extern l1_pgentry_t l1_identmap[L1_PAGETABLE_ENTRIES];
+extern l1_pgentry_t l1_identmap[L1_PAGETABLE_ENTRIES],
+    l1_fixmap[L1_PAGETABLE_ENTRIES];
 void paging_init(void);
 void setup_idle_pagetable(void);
 #endif /* !defined(__ASSEMBLY__) */