linux-kernel - Re: [PATCH 2/2] ata_piix: defer disks to the Hyper-V drivers by default

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Date:	Thu, 19 Apr 2012 19:54:17 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Andy Whitcroft <apw@...onical.com>
CC:	Jeff Garzik <jgarzik@...ox.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Mike Sterling <Mike.Sterling@...rosoft.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 2/2] ata_piix: defer disks to the Hyper-V drivers by default

Hello.

On 04/19/2012 06:33 PM, Andy Whitcroft wrote:

> When we are hosted on a Microsoft Hyper-V hypervisor the guest disks
> are exposed both via the Hyper-V paravirtualised drivers and via an
> emulated SATA disk drive.  In this case we want to use the paravirtualised
> drivers if we can as they are much more efficient.  Note that the Hyper-V
> paravirtualised drivers only expose the virtual hard disk devices, the
> CDROM/DVD devices must still be enumerated.

> Mark the host controller ATA_HOST_IGNORE_ATA to prevent enumeration of
> disk devices.

> BugLink: http://bugs.launchpad.net/bugs/929545
> BugLink: http://bugs.launchpad.net/bugs/942316
> Signed-off-by: Andy Whitcroft<apw@...onical.com>
> ---
>   drivers/ata/ata_piix.c |   36 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 36 insertions(+)

> diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
> index 68013f9..c410ba9 100644
> --- a/drivers/ata/ata_piix.c
> +++ b/drivers/ata/ata_piix.c
> @@ -1552,6 +1552,39 @@ static bool piix_broken_system_poweroff(struct pci_dev *pdev)
>   	return false;
>   }
>
> +static int prefer_ms_hyperv = 1;
> +module_param(prefer_ms_hyperv, int, 0);
> +
> +static void piix_ignore_devices_quirk(struct ata_host *host)
> +{
> +#if defined(CONFIG_HYPERV_STORAGE) || defined(CONFIG_HYPERV_STORAGE_MODULE)

    You could instead use:

#if IS_ENABLED(CONFIG_HYPERV_STORAGE)

> +	static const struct dmi_system_id ignore_hyperv[] = {
> +		{
> +			/* 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.
> +			 */
> +			.ident = "Hyper-V Virtual Machine",
> +			.matches = {
> +				DMI_MATCH(DMI_SYS_VENDOR,
> +						"Microsoft Corporation"),
> +				DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
> +			},
> +		},
> +		{ }	/* terminate list */
> +	};
> +	const struct dmi_system_id *dmi = dmi_first_match(ignore_hyperv);
> +
> +	if (dmi&&  prefer_ms_hyperv) {
> +		host->flags |= ATA_HOST_IGNORE_ATA;
> +		dev_info(host->dev, "%s detected, SATA device ignore set\n",

    s/SATA/ATA/.

MBR, Sergei
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