RE: [PATCH 0/2] Hyper-V disk support V3

[KY Srinivasan <kys@xxxxxxxxxxxxx>]

> -----Original Message-----
> From: Alan Cox [mailto:alan@xxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, April 18, 2012 4:13 PM
> To: KY Srinivasan
> Cc: Andy Whitcroft; Jeff Garzik; linux-ide@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Mike Sterling
> Subject: Re: [PATCH 0/2] Hyper-V disk support V3
> 
> > The notion of "pass through" in Hyper-V  is a little different. IDE devices can be
> configured
> > under either one of the supported controllers and these devices can either be
> virtual disks
> > (VHDs) or physical disks. In either case these will be presented to the guest as
> IDE devices.
> 
> So what ensures that by skipping it at the ATA device level we will
> always find it as a VHD ?

If the Hyper-V storage driver is  present, then the Hyper-V storage driver will
manage the root device (and other devices skipped by the ata driver). 
So, the check if we are running on Hyper-V is not enough
to skip the device in the ata_piix driver; we need to also make sure that the Hyper-V
block driver is available to handle the skipped devices. I think the correct approach here is to
have a kernel (or an ata_piix module parameter) that can be set to override the skipping
of the block device by the ata driver. Distros that are including the Hyper-V storage driver
can set this parameter so that when running on Hyper-V, ata can skip the block device.

Regards,

K. Y
> 
> Alan
> 
> 



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