---

yaml
---
r: 344409
b: refs/heads/master
c: d990434
h: refs/heads/master
i:
  344407: a310fa9
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3100d49d3cd236443faae9d81137c81b22d36003
+refs/heads/master: d9904344fc4052fbe7e4dc137eba0dcdadf326bd

trunk/drivers/ata/ata_piix.c

@@ -1585,12 +1585,31 @@ static void piix_ignore_devices_quirk(struct ata_host *host)
 		},
 		{ }	/* terminate list */
 	};
-	const struct dmi_system_id *dmi = dmi_first_match(ignore_hyperv);
+	static const struct dmi_system_id allow_virtual_pc[] = {
+		{
+			/* In MS Virtual PC guests the DMI ident is nearly
+			 * identical to a Hyper-V guest. One difference is the
+			 * product version which is used here to identify
+			 * a Virtual PC guest. This entry allows ata_piix to
+			 * drive the emulated hardware.
+			 */
+			.ident = "MS Virtual PC 2007",
+			.matches = {
+				DMI_MATCH(DMI_SYS_VENDOR,
+						"Microsoft Corporation"),
+				DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
+				DMI_MATCH(DMI_PRODUCT_VERSION, "VS2005R2"),
+			},
+		},
+		{ }	/* terminate list */
+	};
+	const struct dmi_system_id *ignore = dmi_first_match(ignore_hyperv);
+	const struct dmi_system_id *allow = dmi_first_match(allow_virtual_pc);
 
-	if (dmi && prefer_ms_hyperv) {
+	if (ignore && !allow && prefer_ms_hyperv) {
 		host->flags |= ATA_HOST_IGNORE_ATA;
 		dev_info(host->dev, "%s detected, ATA device ignore set\n",
-			dmi->ident);
+			ignore->ident);
 	}
 #endif
 }