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Re: [Qemu-devel] [PATCH] multiboot: Fix module loading and setting of mm

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] multiboot: Fix module loading and setting of mmap
Date: Wed, 18 Nov 2009 08:35:42 -0600
User-agent: Thunderbird (X11/20090825)

Adam Lackorzynski wrote:

I need to following to fix multiboot booting for me.

Should linuxboot.bin and multiboot.bin end up in pc-bios instead of

Signed-off-by: Adam Lackorzynski <address@hidden>
 hw/pc.c                       |    4 ++--
 pc-bios/optionrom/multiboot.S |    5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/hw/pc.c b/hw/pc.c
index 7c791c4..1c8f95c 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -661,7 +661,7 @@ static int load_multiboot(void *fw_cfg,
/* append module data at the end of last module */
             mb_kernel_data = qemu_realloc(mb_kernel_data,
-                                          mh_load_addr - mb_mod_end);
+                                          mb_mod_end - mh_load_addr);

That bit looks right.

                        mb_kernel_data + mb_mod_start - mh_load_addr);
@@ -720,7 +720,7 @@ static int load_multiboot(void *fw_cfg,
     fw_cfg_add_bytes(fw_cfg, FW_CFG_INITRD_DATA, mb_bootinfo_data,
- option_rom[nb_option_roms] = "multiboot.bin";
+    option_rom[nb_option_roms] = "optionrom/multiboot.bin";

This bit doesn't. multiboot.bin gets installed in ${prefix}/share/. There is a blob shipped in pc-bios/ so if you do -L $srcdir/pc-bios it should work. However, if you did -L $objdir/pc-bios where $objdir != $srcdir, it would not work without your patch. The same is true for seabios and the other roms.

Your patch would break the first two though. I'm not sure we have a great solution.

return 1; /* yes, we are multiboot */
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S
index be5c9fc..9131837 100644
--- a/pc-bios/optionrom/multiboot.S
+++ b/pc-bios/optionrom/multiboot.S
@@ -62,6 +62,9 @@ run_multiboot:
        add             %eax, %ebx
        movl            %ebx, %gs:GS_GDT_DESC + 2
+ xor %eax, %eax
+       mov             %eax, %es
        /* Read the bootinfo struct into RAM */
@@ -71,7 +74,7 @@ run_multiboot:
        mov             %ax, %fs
/* ES = mmap_addr */
-       mov             %eax, %fs:0x48
+       mov             %fs:48, %eax
        shr             $4, %eax
        mov             %ax, %es

This bit needs to be reviewed/acked by Alex.


Anthony Liguori

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