Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio/qemu fixes from Michael S Tsirkin:
 "A couple of fixes for virtio and for the new QEMU fw cfg driver"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  virtio: add VIRTIO_CONFIG_S_NEEDS_RESET device status bit
  MAINTAINERS: add entry for QEMU
  firmware: qemu_fw_cfg.c: hold ACPI global lock during device access
  virtio: virtio 1.0 cs04 spec compliance for reset
  qemu_fw_cfg: don't leak kobj on init error

MAINTAINERS

@@ -9142,6 +9142,13 @@ T:	git git://github.com/KrasnikovEugene/wcn36xx.git
 S:	Supported
 F:	drivers/net/wireless/ath/wcn36xx/
 
+QEMU MACHINE EMULATOR AND VIRTUALIZER SUPPORT
+M:	Gabriel Somlo <somlo@cmu.edu>
+M:	"Michael S. Tsirkin" <mst@redhat.com>
+L:	qemu-devel@nongnu.org
+S:	Maintained
+F:	drivers/firmware/qemu_fw_cfg.c
+
 RADOS BLOCK DEVICE (RBD)
 M:	Ilya Dryomov <idryomov@gmail.com>
 M:	Sage Weil <sage@redhat.com>

drivers/firmware/qemu_fw_cfg.c

@@ -77,12 +77,28 @@ static inline u16 fw_cfg_sel_endianness(u16 key)
 static inline void fw_cfg_read_blob(u16 key,
 				    void *buf, loff_t pos, size_t count)
 {
+	u32 glk;
+	acpi_status status;
+
+	/* If we have ACPI, ensure mutual exclusion against any potential
+	 * device access by the firmware, e.g. via AML methods:
+	 */
+	status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
+	if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
+		/* Should never get here */
+		WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
+		memset(buf, 0, count);
+		return;
+	}
+
 	mutex_lock(&fw_cfg_dev_lock);
 	iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
 	while (pos-- > 0)
 		ioread8(fw_cfg_reg_data);
 	ioread8_rep(fw_cfg_reg_data, buf, count);
 	mutex_unlock(&fw_cfg_dev_lock);
+
+	acpi_release_global_lock(glk);
 }
 
 /* clean up fw_cfg device i/o */
@@ -727,12 +743,18 @@ device_param_cb(mmio, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
 
 static int __init fw_cfg_sysfs_init(void)
 {
+	int ret;
+
 	/* create /sys/firmware/qemu_fw_cfg/ top level directory */
 	fw_cfg_top_ko = kobject_create_and_add("qemu_fw_cfg", firmware_kobj);
 	if (!fw_cfg_top_ko)
 		return -ENOMEM;
 
-	return platform_driver_register(&fw_cfg_sysfs_driver);
+	ret = platform_driver_register(&fw_cfg_sysfs_driver);
+	if (ret)
+		fw_cfg_kobj_cleanup(fw_cfg_top_ko);
+
+	return ret;
 }
 
 static void __exit fw_cfg_sysfs_exit(void)

drivers/virtio/virtio_pci_modern.c

@@ -17,6 +17,7 @@
  *
  */
 
+#include <linux/delay.h>
 #define VIRTIO_PCI_NO_LEGACY
 #include "virtio_pci_common.h"
 
@@ -271,9 +272,13 @@ static void vp_reset(struct virtio_device *vdev)
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	/* 0 status means a reset. */
 	vp_iowrite8(0, &vp_dev->common->device_status);
-	/* Flush out the status write, and flush in device writes,
-	 * including MSI-X interrupts, if any. */
-	vp_ioread8(&vp_dev->common->device_status);
+	/* After writing 0 to device_status, the driver MUST wait for a read of
+	 * device_status to return 0 before reinitializing the device.
+	 * This will flush out the status write, and flush in device writes,
+	 * including MSI-X interrupts, if any.
+	 */
+	while (vp_ioread8(&vp_dev->common->device_status))
+		msleep(1);
 	/* Flush pending VQ/configuration callbacks. */
 	vp_synchronize_vectors(vdev);
 }

include/uapi/linux/virtio_config.h

@@ -40,6 +40,8 @@
 #define VIRTIO_CONFIG_S_DRIVER_OK	4
 /* Driver has finished configuring features */
 #define VIRTIO_CONFIG_S_FEATURES_OK	8
+/* Device entered invalid state, driver must reset it */
+#define VIRTIO_CONFIG_S_NEEDS_RESET	0x40
 /* We've given up on this device. */
 #define VIRTIO_CONFIG_S_FAILED		0x80