[v2] x86: drop use of E801 memory "map" (and alike)

Commit Message

Jan Beulich Jan. 5, 2021, 3:26 p.m. UTC

ACPI mandates use of E820 (or newer, e.g. EFI), and in fact firmware
has been observed to include E820_ACPI ranges in what E801 reports as
available (really "configured") memory. Since all 64-bit systems ought
to support ACPI, drop our use of older BIOS and boot loader interfaces.

Signed-off-by: Jan Beulich <[e-mail]>
---
v2: Drop all use of E801 (and older).

Patch

--- a/xen/arch/x86/boot/mem.S
+++ b/xen/arch/x86/boot/mem.S
@@ -4,8 +4,6 @@ 
 #define E820_BIOS_MAX 128
 
 get_memory_map:
-
-.Lmeme820:
         xorl    %ebx, %ebx                      # continuation counter
         movw    $bootsym(bios_e820map), %di     # point into the whitelist
                                                 # so we can have the bios
@@ -17,14 +15,14 @@  get_memory_map:
         pushw   %ds                             # data record.
         popw    %es
         int     $0x15
-        jc      .Lmem88
+        jc      .Ldone
 
         cmpl    $SMAP,%eax                      # check the return is `SMAP'
-        jne     .Lmem88
+        jne     .Ldone
 
         incw    bootsym(bios_e820nr)
         cmpw    $E820_BIOS_MAX, bootsym(bios_e820nr) # up to this many entries
-        jae     .Lmem88
+        jae     .Ldone
 
         movw    %di,%ax
         addw    $20,%ax
@@ -32,38 +30,7 @@  get_memory_map:
         testl   %ebx,%ebx                       # check to see if
         jnz     1b                              # %ebx is set to EOF
 
-.Lmem88:
-        movb    $0x88, %ah
-        int     $0x15
-        movw    %ax,bootsym(highmem_kb)
-
-.Lmeme801:
-        stc                                     # fix to work around buggy
-        xorw    %cx,%cx                         # BIOSes which don't clear/set
-        xorw    %dx,%dx                         # carry on pass/error of
-                                                # e801h memory size call
-                                                # or merely pass cx,dx though
-                                                # without changing them.
-        movw    $0xe801, %ax
-        int     $0x15
-        jc      .Lint12
-
-        testw   %cx, %cx                        # Kludge to handle BIOSes
-        jnz     1f                              # which report their extended
-        testw   %dx, %dx                        # memory in AX/BX rather than
-        jnz     1f                              # CX/DX.  The spec I have read
-        movw    %ax, %cx                        # seems to indicate AX/BX 
-        movw    %bx, %dx                        # are more reasonable anyway...
-1:      movzwl  %dx, %edx
-        shll    $6,%edx                         # and go from 64k to 1k chunks
-        movzwl  %cx, %ecx
-        addl    %ecx, %edx                      # add in lower memory
-        movl    %edx,bootsym(highmem_kb)        # store extended memory size
-
-.Lint12:
-        int     $0x12
-        movw    %ax,bootsym(lowmem_kb)
-
+.Ldone:
         ret
 
         .align  4
@@ -71,7 +38,3 @@  GLOBAL(bios_e820map)
         .fill   E820_BIOS_MAX*20,1,0
 GLOBAL(bios_e820nr)
         .long   0
-GLOBAL(lowmem_kb)
-        .long   0
-GLOBAL(highmem_kb)
-        .long   0
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1059,28 +1059,6 @@  void __init noreturn __start_xen(unsigne
             bytes += map->size + 4;
         }
     }
-    else if ( bootsym(lowmem_kb) )
-    {
-        memmap_type = "Xen-e801";
-        e820_raw.map[0].addr = 0;
-        e820_raw.map[0].size = bootsym(lowmem_kb) << 10;
-        e820_raw.map[0].type = E820_RAM;
-        e820_raw.map[1].addr = 0x100000;
-        e820_raw.map[1].size = bootsym(highmem_kb) << 10;
-        e820_raw.map[1].type = E820_RAM;
-        e820_raw.nr_map = 2;
-    }
-    else if ( mbi->flags & MBI_MEMLIMITS )
-    {
-        memmap_type = "Multiboot-e801";
-        e820_raw.map[0].addr = 0;
-        e820_raw.map[0].size = mbi->mem_lower << 10;
-        e820_raw.map[0].type = E820_RAM;
-        e820_raw.map[1].addr = 0x100000;
-        e820_raw.map[1].size = mbi->mem_upper << 10;
-        e820_raw.map[1].type = E820_RAM;
-        e820_raw.nr_map = 2;
-    }
     else
         panic("Bootloader provided no memory information\n");
 
--- a/xen/include/asm-x86/e820.h
+++ b/xen/include/asm-x86/e820.h
@@ -36,7 +36,6 @@  extern struct e820map e820;
 extern struct e820map e820_raw;
 
 /* These symbols live in the boot trampoline. */
-extern unsigned int lowmem_kb, highmem_kb;
 extern struct e820map bios_e820map[];
 extern unsigned int bios_e820nr;