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

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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.

Signed-off-by: Andy Whitcroft<apw@xxxxxxxxxxxxx>
  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)

   You could instead use:


+	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 = {
+						"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",


MBR, Sergei
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