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multiboot: Calculate upper_mem in the ROM

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The upper_mem field of the Multiboot information struct doesn't really
contain the RAM size - 1 MB like we used to calculate it, but only the
memory from 1 MB up to the first (upper) memory hole.

In order to correctly retrieve this information, the multiboot ROM now
looks at the mmap it creates anyway and tries to find the size of
contiguous usable memory from 1 MB.

Drop the multiboot.c definition of lower_mem and upper_mem because both
are queried at runtime now.

Signed-off-by: Kevin Wolf <mail@kevin-wolf.de>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1372018066-21822-3-git-send-email-mail@kevin-wolf.de
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Kevin Wolf 2013-06-23 22:07:45 +02:00 committed by Anthony Liguori
parent 390fb6b471
commit 26a8ec0761
2 changed files with 40 additions and 2 deletions
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2
hw/i386/multiboot.c
View file

@ -315,8 +315,6 @@ int load_multiboot(FWCfgState *fw_cfg,
| MULTIBOOT_FLAGS_CMDLINE
| MULTIBOOT_FLAGS_MODULES
| MULTIBOOT_FLAGS_MMAP);
stl_p(bootinfo + MBI_MEM_LOWER, 640);
stl_p(bootinfo + MBI_MEM_UPPER, (ram_size / 1024) - 1024);
stl_p(bootinfo + MBI_BOOT_DEVICE, 0x8000ffff); /* XXX: use the -boot switch? */
stl_p(bootinfo + MBI_MMAP_ADDR, ADDR_E820_MAP);

40
pc-bios/optionrom/multiboot.S
View file

@ -123,6 +123,46 @@ mmap_store_entry:
jnz mmap_loop
mmap_done:
/* Calculate upper_mem field: The amount of memory between 1 MB and
the first upper memory hole. Get it from the mmap. */
xor %di, %di
mov $0x100000, %edx
upper_mem_entry:
cmp %fs:0x2c, %di
je upper_mem_done
add $4, %di
/* Skip if type != 1 */
cmpl $1, %es:16(%di)
jne upper_mem_next
/* Skip if > 4 GB */
movl %es:4(%di), %eax
test %eax, %eax
jnz upper_mem_next
/* Check for contiguous extension (base <= %edx < base + length) */
movl %es:(%di), %eax
cmp %eax, %edx
jb upper_mem_next
addl %es:8(%di), %eax
cmp %eax, %edx
jae upper_mem_next
/* If so, update %edx, and restart the search (mmap isn't ordered) */
mov %eax, %edx
xor %di, %di
jmp upper_mem_entry
upper_mem_next:
addl %es:-4(%di), %edi
jmp upper_mem_entry
upper_mem_done:
sub $0x100000, %edx
shr $10, %edx
mov %edx, %fs:0x8
real_to_prot:
/* Load the GDT before going into protected mode */
lgdt: