Виктор Мясников ( Victor Miasnikov)

==
The virtual motherboard that is used by Hyper-V has a dual port, dual channel IDE controller based on the 440BX chipset.
This motherboard was chosen as the baseline platform for emulation due to the extensive driver support present across a
wide variety of operating systems.
When a virtual machine boots on Hyper-V, it is required to boot off the IDE disk (as the paravirtualized SCSI controller
isn’t recognized by the virtualized BIOS).
Therefore, when the ata_piix module gets loaded in Linux, it recognizes the hard disk connected to it.
When the Hyper-V guest-side drivers are loaded (specifically hv_storvsc),
it enumerates both the IDE as well as SCSI busses that are present in the system and provides faster access to those
disks using the paravirtualized device model.
==

{
Linux v3.1 Era:

==
The virtual motherboard that is used by Hyper-V has a dual port, dual channel IDE controller based on the 440BX chipset.
This motherboard was chosen as the baseline platform for emulation due to the extensive driver support present across a
wide variety of operating systems.
When a virtual machine boots on Hyper-V, it is required to boot off the IDE disk (as the paravirtualized SCSI controller
isn’t recognized by the virtualized BIOS).
Therefore, when the ata_piix module gets loaded in Linux, it recognizes the hard disk connected to it.
When the Hyper-V guest-side drivers ( hv_storvsc, about hv_blkvsc see later) are loaded ,
it enumerates [VVM: only] SCSI buss[es] that are present in the system and provides faster access to those disks using
the
paravirtualized device model.
In this case, all the drivers are working as intended – there is [ VVM: _really_ ] no bug here.

But if the Hyper-V guest-side _run_ driver hv_blkvsc
it enumerates ATA(IDE) buss[es] that are present in the system and provides faster access to those disks using the
paravirtualized device model.

In this case, we are get the problem is that ata_piix and hv_blkvsc both claim the (virtual) hard disk. i.e. bug ( i.e.
variant "issue described by Maksim Kramarenko" see later).
==

}


{
Linux v3.2 . . v3.4.2 Era
( except OpenSUSE , Ubuntu 12.04 , etc. with 1b) db63a4c8115a libata 1) cd006086fa5d ata_piix ):

==
The virtual motherboard that is used by Hyper-V has a dual port, dual channel IDE controller based on the 440BX chipset.
This motherboard was chosen as the baseline platform for emulation due to the extensive driver support present across a
wide variety of operating systems.
When a virtual machine boots on Hyper-V, it is required to boot off the IDE disk (as the paravirtualized SCSI controller
isn’t recognized by the virtualized BIOS).
Therefore, when the ata_piix module gets loaded in Linux, it recognizes the hard disk connected to it.
When the Hyper-V guest-side drivers are loaded (specifically hv_storvsc),
it enumerates both the IDE as well as SCSI busses that are present in the system and provides faster access to those
disks using the paravirtualized device model.

No "In this case, all the drivers are working as intended – there is no bug here."
but we are has problem:

—– Original Message —–
From: "Jonathan Nieder"
To: . . . Cc: . . .
Sent: Tuesday, June 05, 2012 7:59 AM
Subject: Re: [PATCH 2/2] ata_piix: defer disks to the Hyper-V drivers by default

. . .

If I understand correctly,
the problem is that ata_piix and hv_storvsc both claim the (virtual) hard disk.
==

and
==
+ see tranlate from Russian language issue described by Maksim Kramarenko:
http://lists.debian.org/debian-russian/2012/01/msg00324.html

. . .

>> Errors do not interfere with work, but sneaking suspicion about
>> future problems with the hard drive …
[...]
>> in general, the source of the problem as follows:
>> After [VVM: turn On in kernel source] Hyper-V modules [compile and
>> start use], a hard disk was determined as 2 with the same UUID.
[...]
>> connected to a drive:
>> http://www.k-max.name/wp-content/uploads/2012/01/hdd-e1327750214479.png
>> it is defined as a 2:
>> http://www.k-max.name/wp-content/uploads/2012/01/2hdd.png
>> Naturally, the same UUID:
>> http://www.k-max.name/wp-content/uploads/2012/01/blkid.png
>> That’s what tells us the directory / dev:
>> http://www.k-max.name/wp-content/uploads/2012/01/uuid.png

==



==
}


{
Linux v3.5 Era + v3.4.3 – v3.4.X and OpenSUSE , Ubuntu 12.04 :

==
The virtual motherboard that is used by Hyper-V has a dual port, dual channel IDE controller based on the 440BX chipset.
This motherboard was chosen as the baseline platform for emulation due to the extensive driver support present across a
wide variety of operating systems.
When a virtual machine boots on Hyper-V, it is required to boot off the IDE disk (as the paravirtualized SCSI controller
isn’t recognized by the virtualized BIOS).
Therefore, when the ata_piix module [ VVM: _with_ 1b) db63a4c8115a libata 1) cd006086fa5d ata_piix] gets loaded in
Linux, it recognizes what the hard disk [VVM: handled by hv_storvsc].

The patch [ VVM: patches 1b) db63a4c8115a libata 1) cd006086fa5d ata_piix] that Andy has submitted is an enhancement to
the ata_piix module
that will detect if the OS is running on top of a Hyper-V hypervisor
and defer the block device handling in favor of letting hv_storvsc enumerate and handle the disks attached to the IDE
ports.


When the Hyper-V guest-side drivers are loaded (specifically hv_storvsc),
it enumerates both the IDE as well as SCSI busses that are present in the system and provides faster access to those
disks using the paravirtualized device model.
In this case, all the drivers are working as intended – there is [ VVM: _really_ ] no bug here.

==

}