This is a request for testers, specifically people whose i386 or
x86_64 systems won't boot properly if CONFIG_EDD=[ym] without the use
of edd=skipmbr. If you're currently using edd=skipmbr, I'd really
appreciate knowing about it, and your results of booting with this
patch.
This patch uses an int13 Get Disk Type call before using a Read
Sectors call to read the MBR. If Get Disk Type fails, this is a good
indication that the BIOS doesn't believe there's a disk there, without
actually trying to do I/O to the disk.
arch/i386/boot/edd.S | 15 ++++++++++++++-
include/linux/edd.h | 2 ++
2 files changed, 16 insertions, 1 deletion
Signed-off-by: Matt Domsch <[email protected]>
Thanks,
Matt
--
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
diff --git a/arch/i386/boot/edd.S b/arch/i386/boot/edd.S
--- a/arch/i386/boot/edd.S
+++ b/arch/i386/boot/edd.S
@@ -55,6 +55,19 @@ done_cl:
# Read the first sector of each BIOS disk device and store the 4-byte signature
edd_mbr_sig_start:
movb $0x80, %dl # from device 80
+edd_get_disk_type:
+ movw $GET_DISK_TYPE, %ax
+ pushw %cx # this clobbers cx and dx
+ pushw %dx #
+ stc # work around buggy BIOSes
+ int $0x13
+ sti # work around buggy BIOSes
+ popw %dx
+ popw %cx
+ jc edd_mbr_sig_done
+ cmpb $GET_DISK_TYPE_DISK, %ah # is this a disk?
+ jne edd_mbr_sig_done
+
movw $EDD_MBR_SIG_BUF, %bx # store buffer ptr in bx
edd_mbr_sig_read:
movl $0xFFFFFFFF, %eax
@@ -82,7 +95,7 @@ edd_mbr_sig_read:
incb %dl # increment to next device
addw $4, %bx # increment sig buffer ptr
cmpb $EDD_MBR_SIG_MAX, (EDD_MBR_SIG_NR_BUF) # Out of space?
- jb edd_mbr_sig_read # keep looping
+ jb edd_get_disk_type # keep looping
edd_mbr_sig_done:
# Do the BIOS Enhanced Disk Drive calls
diff --git a/include/linux/edd.h b/include/linux/edd.h
--- a/include/linux/edd.h
+++ b/include/linux/edd.h
@@ -39,6 +39,8 @@
#define CHECKEXTENSIONSPRESENT 0x41
#define GETDEVICEPARAMETERS 0x48
#define LEGACYGETDEVICEPARAMETERS 0x08
+#define GET_DISK_TYPE 0x1500
+#define GET_DISK_TYPE_DISK 0x03
#define EDDMAGIC1 0x55AA
#define EDDMAGIC2 0xAA55
-
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