Re: [Qemu-devel] [PATCH for 2.5? 1/1] DSDT: add floppy-related objects

["Denis V. Lunev" <den@openvz.org>]

On 12/14/2015 12:21 PM, Michael S. Tsirkin wrote:
> On Mon, Dec 14, 2015 at 11:22:39AM +0300, Denis V. Lunev wrote:
>> From: Roman Kagan <rkagan@virtuozzo.com>
>>
>> On x86-based systems Linux determines the presence and the type of
>> floppy drives via a query of a CMOS field.  So does SeaBIOS when
>> populating the return data for int 0x13 function 0x08.
>>
>> Windows doesn't; instead, it requests this information from BIOS via int
>> 0x13/0x08 or through ACPI objects _FDE (Floppy Drive Enumerate) and _FDI
>> (Floppy Drive Information).  On UEFI systems only ACPI-based detection
>> is supported.
>>
>> QEMU used not to provide those objects in its DSDT; as a result floppy
>> drives were invisible to Windows on UEFI/OVMF.
>>
>> This patch implements those objects in ASL, making the ACPI interpreter
>> query the CMOS field and populate the objects.  The data values used for
>> _FDI (which, per ACPI spec, is supposed to be equivalent to BIOS int
>> 0x13/0x08) are taken from SeaBIOS.
>>
>> Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Michael S. Tsirkin <mst@redhat.com>
>> CC: Igor Mammedov <imammedo@redhat.com>
>> CC: Paolo Bonzini <pbonzini@redhat.com>
>> CC: Richard Henderson <rth@twiddle.net>
>> CC: Eduardo Habkost <ehabkost@redhat.com>
> This is not a regression, so I'm inclined not to merge this for 2.5.
> Pls correct me if I'm wrong.
>

this was a question actually.

Yes, this is not a regression but user observable bug. The floppy
is not available in Windows UEFI guests and it is not that easy
to get VirtIO drivers in this case installed especially for root
disk.

Den