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Re: [Qemu-devel] [PATCH v3 05/16] pc: Make -no-fd-bootchk stick across b
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v3 05/16] pc: Make -no-fd-bootchk stick across boot order changes |
Date: |
Tue, 18 Jun 2013 13:39:25 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) |
Anthony Liguori <address@hidden> writes:
> Markus Armbruster <address@hidden> writes:
>
>> Option -no-fd-bootchk asks the BIOS to attempt booting from a floppy
>> even when the boot sector signature isn't there, by setting a bit in
>> RTC CMOS. It was added back in 2006 (commit 52ca8d6a).
>>
>> Two years later, commit 0ecdffbb added monitor command boot_set.
>> Implemented by new function pc_boot_set(). It unconditionally clears
>> the floppy signature bit in CMOS.
>>
>> Commit e0f084bf added -boot option once to automatically change the
>> boot order on first reset. Reuses pc_boot_set(), thus also clears the
>> floppy signature bit. Commit d9346e81 took care to preserve this
>> behavior.
>
> Quite a history there :-)
>
> Does anyone still use no-fd-bootchk?
No idea.
> Do you know what the original
> use-case was?
Its commit message is of no help. Best we got is the option
documentation:
Disable boot signature checking for floppy disks in Bochs BIOS. It
may be needed to boot from old floppy disks.
As far as I can tell, SeaBIOS implements this, too.
>> Thus, -no-fd-bootchk applies to any number of boots. Except it
>> applies just to the first boot with -boot once, and never after
>> boot_set. Weird. Make it stick instead: set the bit according to
>> -no-fd-bootchk in pc_boot_set().
>>
>> Signed-off-by: Markus Armbruster <address@hidden>
>
> Reviewed-by: Anthony Liguori <address@hidden>
Thanks!
- [Qemu-devel] [PATCH v3 04/16] vl: Rename *boot_devices to *boot_order, for consistency, (continued)
- [Qemu-devel] [PATCH v3 04/16] vl: Rename *boot_devices to *boot_order, for consistency, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 02/16] qemu-option: check_params() is now unused, drop it, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 01/16] vl: Clean up parsing of -boot option argument, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 10/16] boot-order-test: Cover -boot once in ppc tests, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 05/16] pc: Make -no-fd-bootchk stick across boot order changes, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 07/16] qtest: Don't reset on qtest chardev connect, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 13/16] boot-order-test: Add tests for PowerPC PREP, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 08/16] boot-order-test: New; covering just PC for now, Markus Armbruster, 2013/06/14
- [Qemu-devel] [PATCH v3 03/16] vl: Fix -boot order and once regressions, and related bugs, Markus Armbruster, 2013/06/14