From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH 2/2] ata_piix: defer disks to the Hyper-V drivers by
 default
Date: Sat, 14 Apr 2012 17:02:23 +0100
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Cc: Jeff Garzik <jgarzik@pobox.com>, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" <kys@microsoft.com>, Mike Sterling <Mike.Sterling@microsoft.com>

O> +#ifdef CONFIG_X86
> +	/* On Hyper-V hypervisors the disks are exposed on both the emulated
> +	 * SATA controller and on the paravirtualised drivers.  The CD/DVD
> +	 * devices are only exposed on the emulated controller.  Request we
> +	 * ignore ATA devices on this host.
> +	 */
> +	if (prefer_ms_hyperv && x86_hyper == &x86_hyper_ms_hyperv) {
> +		host->flags |= ATA_HOST_IGNORE_ATA;
> +		dev_info(&pdev->dev, "Hyper-V hypervisor detected, ignoring ATA disks\n");
> +	}
> +#endif

Does hyper-v not set its own unique and identifable pci
subvendor/subdevice ?

Alan