[PATCH v8 5/6] Add simple sample driver for mediated device framework

Kirti Wankhede
2016-10-10T20:27:53Z

Sample driver creates mdev device that simulates serial port over PCI card.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Neo Jia <cjia@nvidia.com>
Change-Id: I857f8f12f8b275f2498dfe8c628a5cdc7193b1b2
---
Documentation/vfio-mdev/Makefile | 14 +
Documentation/vfio-mdev/mtty.c | 1353 ++++++++++++++++++++++
Documentation/vfio-mdev/vfio-mediated-device.txt | 63 +
3 files changed, 1430 insertions(+)
create mode 100644 Documentation/vfio-mdev/Makefile
create mode 100644 Documentation/vfio-mdev/mtty.c

diff --git a/Documentation/vfio-mdev/Makefile b/Documentation/vfio-mdev/Makefile
new file mode 100644
index 000000000000..ff6f8a324c85
--- /dev/null
+++ b/Documentation/vfio-mdev/Makefile
@@ -0,0 +1,14 @@
+#
+# Makefile for mtty.c file
+#
+KDIR:=/lib/modules/$(shell uname -r)/build
+
+obj-m:=mtty.o
+
+default:
+ $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
+
+clean:
+ @rm -rf .*.cmd *.mod.c *.o *.ko .tmp*
+ @rm -rf Module.* Modules.* modules.* .tmp_versions
+
diff --git a/Documentation/vfio-mdev/mtty.c b/Documentation/vfio-mdev/mtty.c
new file mode 100644
index 000000000000..497c90ebe257
--- /dev/null
+++ b/Documentation/vfio-mdev/mtty.c
@@ -0,0 +1,1353 @@
+/*
+ * Mediated virtual PCI serial host device driver
+ *
+ * Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
+ * Author: Neo Jia <cjia@nvidia.com>
+ * Kirti Wankhede <kwankhede@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Sample driver that creates mdev device that simulates serial port over PCI
+ * card.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/cdev.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/uuid.h>
+#include <linux/vfio.h>
+#include <linux/iommu.h>
+#include <linux/sysfs.h>
+#include <linux/ctype.h>
+#include <linux/file.h>
+#include <linux/mdev.h>
+#include <linux/pci.h>
+#include <linux/serial.h>
+#include <uapi/linux/serial_reg.h>
+/*
+ * #defines
+ */
+
+#define VERSION_STRING "0.1"
+#define DRIVER_AUTHOR "NVIDIA Corporation"
+
+#define MTTY_CLASS_NAME "mtty"
+
+#define MTTY_NAME "mtty"
+
+#define MTTY_CONFIG_SPACE_SIZE 0xff
+#define MTTY_IO_BAR_SIZE 0x8
+#define MTTY_MMIO_BAR_SIZE 0x100000
+
+#define STORE_LE16(addr, val) (*(u16 *)addr = val)
+#define STORE_LE32(addr, val) (*(u32 *)addr = val)
+
+#define MAX_FIFO_SIZE 16
+
+#define CIRCULAR_BUF_INC_IDX(idx) (idx = (idx + 1) & (MAX_FIFO_SIZE - 1))
+
+#define MTTY_VFIO_PCI_OFFSET_SHIFT 40
+
+#define MTTY_VFIO_PCI_OFFSET_TO_INDEX(off) (off >> MTTY_VFIO_PCI_OFFSET_SHIFT)
+#define MTTY_VFIO_PCI_INDEX_TO_OFFSET(index) \
+ ((u64)(index) << MTTY_VFIO_PCI_OFFSET_SHIFT)
+#define MTTY_VFIO_PCI_OFFSET_MASK \
+ (((u64)(1) << MTTY_VFIO_PCI_OFFSET_SHIFT) - 1)
+
+
+/*
+ * Global Structures
+ */
+
+struct mtty_dev {
+ dev_t vd_devt;
+ struct class *vd_class;
+ struct cdev vd_cdev;
+ struct idr vd_idr;
+ struct device dev;
+} mtty_dev;
+
+struct mdev_region_info {
+ u64 start;
+ u64 phys_start;
+ u32 size;
+ u64 vfio_offset;
+};
+
+#if defined(DEBUG_REGS)
+const char *wr_reg[] = {
+ "TX",
+ "IER",
+ "FCR",
+ "LCR",
+ "MCR",
+ "LSR",
+ "MSR",
+ "SCR"
+};
+
+const char *rd_reg[] = {
+ "RX",
+ "IER",
+ "IIR",
+ "LCR",
+ "MCR",
+ "LSR",
+ "MSR",
+ "SCR"
+};
+#endif
+
+/* loop back buffer */
+struct rxtx {
+ u8 fifo[MAX_FIFO_SIZE];
+ u8 head, tail;
+ u8 count;
+};
+
+struct serial_port {
+ u8 uart_reg[8]; /* 8 registers */
+ struct rxtx rxtx; /* loop back buffer */
+ bool dlab;
+ bool overrun;
+ u16 divisor;
+ u8 fcr; /* FIFO control register */
+ u8 max_fifo_size;
+ u8 intr_trigger_level; /* interrupt trigger level */
+};
+
+/* State of each mdev device */
+struct mdev_state {
+ int irq_fd;
+ struct file *intx_file;
+ struct file *msi_file;
+ int irq_index;
+ u8 *vconfig;
+ struct mutex ops_lock;
+ struct mdev_device *mdev;
+ struct mdev_region_info region_info[VFIO_PCI_NUM_REGIONS];
+ u32 bar_mask[VFIO_PCI_NUM_REGIONS];
+ struct list_head next;
+ struct serial_port s[2];
+ struct mutex rxtx_lock;
+ struct vfio_device_info dev_info;
+};
+
+struct mutex mdev_list_lock;
+struct list_head mdev_devices_list;
+
+static const struct file_operations vd_fops = {
+ .owner = THIS_MODULE,
+};
+
+/* function prototypes */
+
+static int mtty_trigger_interrupt(uuid_le uuid);
+
+/* Helper functions */
+static struct mdev_state *find_mdev_state_by_uuid(uuid_le uuid)
+{
+ struct mdev_state *mds;
+
+ list_for_each_entry(mds, &mdev_devices_list, next) {
+ if (uuid_le_cmp(mds->mdev->uuid, uuid) == 0)
+ return mds;
+ }
+
+ return NULL;
+}
+
+void dump_buffer(char *buf, uint32_t count)
+{
+#if defined(DEBUG)
+ int i;
+
+ pr_info("Buffer:\n");
+ for (i = 0; i < count; i++) {
+ pr_info("%2x ", *(buf + i));
+ if ((i + 1) % 16 == 0)
+ pr_info("\n");
+ }
+#endif
+}
+
+static void mtty_create_config_space(struct mdev_state *mdev_state)
+{
+ /* PCI dev ID */
+ STORE_LE32((u32 *) &mdev_state->vconfig[0x0], 0x32534348);
+
+ /* Control: I/O+, Mem-, BusMaster- */
+ STORE_LE16((u16 *) &mdev_state->vconfig[0x4], 0x0001);
+
+ /* Status: capabilities list absent */
+ STORE_LE16((u16 *) &mdev_state->vconfig[0x6], 0x0200);
+
+ /* Rev ID */
+ mdev_state->vconfig[0x8] = 0x10;
+
+ /* programming interface class : 16550-compatible serial controller */
+ mdev_state->vconfig[0x9] = 0x02;
+
+ /* Sub class : 00 */
+ mdev_state->vconfig[0xa] = 0x00;
+
+ /* Base class : Simple Communication controllers */
+ mdev_state->vconfig[0xb] = 0x07;
+
+ /* base address registers */
+ /* BAR0: IO space */
+ STORE_LE32((u32 *) &mdev_state->vconfig[0x10], 0x000001);
+ mdev_state->bar_mask[0] = ~(MTTY_IO_BAR_SIZE) + 1;
+
+ /* BAR1: IO space */
+ STORE_LE32((u32 *) &mdev_state->vconfig[0x14], 0x000001);
+ mdev_state->bar_mask[1] = ~(MTTY_IO_BAR_SIZE) + 1;
+
+ /* Subsystem ID */
+ STORE_LE32((u32 *) &mdev_state->vconfig[0x2c], 0x32534348);
+
+ mdev_state->vconfig[0x34] = 0x00; /* Cap Ptr */
+ mdev_state->vconfig[0x3d] = 0x01; /* interrupt pin (INTA#) */
+
+ /* Vendor specific data */
+ mdev_state->vconfig[0x40] = 0x23;
+ mdev_state->vconfig[0x43] = 0x80;
+ mdev_state->vconfig[0x44] = 0x23;
+ mdev_state->vconfig[0x48] = 0x23;
+ mdev_state->vconfig[0x4c] = 0x23;
+
+ mdev_state->vconfig[0x60] = 0x50;
+ mdev_state->vconfig[0x61] = 0x43;
+ mdev_state->vconfig[0x62] = 0x49;
+ mdev_state->vconfig[0x63] = 0x20;
+ mdev_state->vconfig[0x64] = 0x53;
+ mdev_state->vconfig[0x65] = 0x65;
+ mdev_state->vconfig[0x66] = 0x72;
+ mdev_state->vconfig[0x67] = 0x69;
+ mdev_state->vconfig[0x68] = 0x61;
+ mdev_state->vconfig[0x69] = 0x6c;
+ mdev_state->vconfig[0x6a] = 0x2f;
+ mdev_state->vconfig[0x6b] = 0x55;
+ mdev_state->vconfig[0x6c] = 0x41;
+ mdev_state->vconfig[0x6d] = 0x52;
+ mdev_state->vconfig[0x6e] = 0x54;
+}
+
+static void handle_pci_cfg_write(struct mdev_state *mdev_state, u16 offset,
+ char *buf, u32 count)
+{
+ u32 cfg_addr, bar_mask, bar_index = 0;
+
+ switch (offset) {
+ case 0x04: /* device control */
+ case 0x06: /* device status */
+ /* do nothing */
+ break;
+ case 0x3c: /* interrupt line */
+ mdev_state->vconfig[0x3c] = buf[0];
+ break;
+ case 0x3d:
+ /*
+ * Interrupt Pin is hardwired to INTA.
+ * This field is write protected by hardware
+ */
+ break;
+ case 0x10: /* BAR0 */
+ case 0x14: /* BAR1 */
+ if (offset == 0x10)
+ bar_index = 0;
+ else if (offset == 0x14)
+ bar_index = 1;
+
+ cfg_addr = *(u32 *)buf;
+ pr_info("BAR%d addr 0x%x\n", bar_index, cfg_addr);
+
+ if (cfg_addr == 0xffffffff) {
+ bar_mask = mdev_state->bar_mask[bar_index];
+ cfg_addr = (cfg_addr & bar_mask);
+ }
+
+ cfg_addr |= (mdev_state->vconfig[offset] & 0x3ul);
+ STORE_LE32(&mdev_state->vconfig[offset], cfg_addr);
+ break;
+ case 0x18: /* BAR2 */
+ case 0x1c: /* BAR3 */
+ case 0x20: /* BAR4 */
+ STORE_LE32(&mdev_state->vconfig[offset], 0);
+ break;
+ default:
+ pr_info("PCI config write @0x%x of %d bytes not handled\n",
+ offset, count);
+ break;
+ }
+}
+
+static void handle_bar_write(unsigned int index, struct mdev_state *mdev_state,
+ u16 offset, char *buf, u32 count)
+{
+ u8 data = *buf;
+
+ /* Handle data written by guest */
+ switch (offset) {
+ case UART_TX:
+ /* if DLAB set, data is LSB of divisor */
+ if (mdev_state->s[index].dlab) {
+ mdev_state->s[index].divisor |= data;
+ break;
+ }
+
+ mutex_lock(&mdev_state->rxtx_lock);
+
+ /* save in TX buffer */
+ if (mdev_state->s[index].rxtx.count <
+ mdev_state->s[index].max_fifo_size) {
+ mdev_state->s[index].rxtx.fifo[
+ mdev_state->s[index].rxtx.head] = data;
+ mdev_state->s[index].rxtx.count++;
+ CIRCULAR_BUF_INC_IDX(mdev_state->s[index].rxtx.head);
+ mdev_state->s[index].overrun = false;
+
+ /*
+ * Trigger interrupt if receive data interrupt is
+ * enabled and fifo reached trigger level
+ */
+ if ((mdev_state->s[index].uart_reg[UART_IER] &
+ UART_IER_RDI) &&
+ (mdev_state->s[index].rxtx.count ==
+ mdev_state->s[index].intr_trigger_level)) {
+ /* trigger interrupt */
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: Fifo level trigger\n",
+ index);
+#endif
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+ } else {
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: Buffer Overflow\n", index);
+#endif
+ mdev_state->s[index].overrun = true;
+
+ /*
+ * Trigger interrupt if receiver line status interrupt
+ * is enabled
+ */
+ if (mdev_state->s[index].uart_reg[UART_IER] &
+ UART_IER_RLSI)
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+ mutex_unlock(&mdev_state->rxtx_lock);
+ break;
+
+ case UART_IER:
+ /* if DLAB set, data is MSB of divisor */
+ if (mdev_state->s[index].dlab)
+ mdev_state->s[index].divisor |= (u16)data << 8;
+ else {
+ mdev_state->s[index].uart_reg[offset] = data;
+ mutex_lock(&mdev_state->rxtx_lock);
+ if ((data & UART_IER_THRI) &&
+ (mdev_state->s[index].rxtx.head ==
+ mdev_state->s[index].rxtx.tail)) {
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: IER_THRI write\n",
+ index);
+#endif
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+
+ mutex_unlock(&mdev_state->rxtx_lock);
+ }
+
+ break;
+
+ case UART_FCR:
+ mdev_state->s[index].fcr = data;
+
+ mutex_lock(&mdev_state->rxtx_lock);
+ if (data & (UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT)) {
+ /* clear loop back FIFO */
+ mdev_state->s[index].rxtx.count = 0;
+ mdev_state->s[index].rxtx.head = 0;
+ mdev_state->s[index].rxtx.tail = 0;
+ }
+ mutex_unlock(&mdev_state->rxtx_lock);
+
+ switch (data & UART_FCR_TRIGGER_MASK) {
+ case UART_FCR_TRIGGER_1:
+ mdev_state->s[index].intr_trigger_level = 1;
+ break;
+
+ case UART_FCR_TRIGGER_4:
+ mdev_state->s[index].intr_trigger_level = 4;
+ break;
+
+ case UART_FCR_TRIGGER_8:
+ mdev_state->s[index].intr_trigger_level = 8;
+ break;
+
+ case UART_FCR_TRIGGER_14:
+ mdev_state->s[index].intr_trigger_level = 14;
+ break;
+ }
+
+ /*
+ * Set trigger level to 1 otherwise or implement timer with
+ * timeout of 4 characters and on expiring that timer set
+ * Recevice data timeout in IIR register
+ */
+ mdev_state->s[index].intr_trigger_level = 1;
+ if (data & UART_FCR_ENABLE_FIFO)
+ mdev_state->s[index].max_fifo_size = MAX_FIFO_SIZE;
+ else {
+ mdev_state->s[index].max_fifo_size = 1;
+ mdev_state->s[index].intr_trigger_level = 1;
+ }
+
+ break;
+
+ case UART_LCR:
+ if (data & UART_LCR_DLAB) {
+ mdev_state->s[index].dlab = true;
+ mdev_state->s[index].divisor = 0;
+ } else
+ mdev_state->s[index].dlab = false;
+
+ mdev_state->s[index].uart_reg[offset] = data;
+ break;
+
+ case UART_MCR:
+ mdev_state->s[index].uart_reg[offset] = data;
+
+ if ((mdev_state->s[index].uart_reg[UART_IER] & UART_IER_MSI) &&
+ (data & UART_MCR_OUT2)) {
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: MCR_OUT2 write\n", index);
+#endif
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+
+ if ((mdev_state->s[index].uart_reg[UART_IER] & UART_IER_MSI) &&
+ (data & (UART_MCR_RTS | UART_MCR_DTR))) {
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: MCR RTS/DTR write\n", index);
+#endif
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+ break;
+
+ case UART_LSR:
+ case UART_MSR:
+ /* do nothing */
+ break;
+
+ case UART_SCR:
+ mdev_state->s[index].uart_reg[offset] = data;
+ break;
+
+ default:
+ break;
+ }
+}
+
+static void handle_bar_read(unsigned int index, struct mdev_state *mdev_state,
+ u16 offset, char *buf, u32 count)
+{
+ /* Handle read requests by guest */
+ switch (offset) {
+ case UART_RX:
+ /* if DLAB set, data is LSB of divisor */
+ if (mdev_state->s[index].dlab) {
+ *buf = (u8)mdev_state->s[index].divisor;
+ break;
+ }
+
+ mutex_lock(&mdev_state->rxtx_lock);
+ /* return data in tx buffer */
+ if (mdev_state->s[index].rxtx.head !=
+ mdev_state->s[index].rxtx.tail) {
+ *buf = mdev_state->s[index].rxtx.fifo[
+ mdev_state->s[index].rxtx.tail];
+ mdev_state->s[index].rxtx.count--;
+ CIRCULAR_BUF_INC_IDX(mdev_state->s[index].rxtx.tail);
+ }
+
+ if (mdev_state->s[index].rxtx.head ==
+ mdev_state->s[index].rxtx.tail) {
+ /*
+ * Trigger interrupt if tx buffer empty interrupt is
+ * enabled and fifo is empty
+ */
+#if defined(DEBUG_INTR)
+ pr_err("Serial port %d: Buffer Empty\n", index);
+#endif
+ if (mdev_state->s[index].uart_reg[UART_IER] &
+ UART_IER_THRI)
+ mtty_trigger_interrupt(mdev_state->mdev->uuid);
+ }
+ mutex_unlock(&mdev_state->rxtx_lock);
+
+ break;
+
+ case UART_IER:
+ if (mdev_state->s[index].dlab) {
+ *buf = (u8)(mdev_state->s[index].divisor >> 8);
+ break;
+ }
+ *buf = mdev_state->s[index].uart_reg[offset] & 0x0f;
+ break;
+
+ case UART_IIR:
+ {
+ u8 ier = mdev_state->s[index].uart_reg[UART_IER];
+ *buf = 0;
+
+ mutex_lock(&mdev_state->rxtx_lock);
+ /* Interrupt priority 1: Parity, overrun, framing or break */
+ if ((ier & UART_IER_RLSI) && mdev_state->s[index].overrun)
+ *buf |= UART_IIR_RLSI;
+
+ /* Interrupt priority 2: Fifo trigger level reached */
+ if ((ier & UART_IER_RDI) &&
+ (mdev_state->s[index].rxtx.count ==
+ mdev_state->s[index].intr_trigger_level))
+ *buf |= UART_IIR_RDI;
+
+ /* Interrupt priotiry 3: transmitter holding register empty */
+ if ((ier & UART_IER_THRI) &&
+ (mdev_state->s[index].rxtx.head ==
+ mdev_state->s[index].rxtx.tail))
+ *buf |= UART_IIR_THRI;
+
+ /* Interrupt priotiry 4: Modem status: CTS, DSR, RI or DCD */
+ if ((ier & UART_IER_MSI) &&
+ (mdev_state->s[index].uart_reg[UART_MCR] &
+ (UART_MCR_RTS | UART_MCR_DTR)))
+ *buf |= UART_IIR_MSI;
+
+ /* bit0: 0=> interrupt pending, 1=> no interrupt is pending */
+ if (*buf == 0)
+ *buf = UART_IIR_NO_INT;
+
+ /* set bit 6 & 7 to be 16550 compatible */
+ *buf |= 0xC0;
+ mutex_unlock(&mdev_state->rxtx_lock);
+ }
+ break;
+
+ case UART_LCR:
+ case UART_MCR:
+ *buf = mdev_state->s[index].uart_reg[offset];
+ break;
+
+ case UART_LSR:
+ {
+ u8 lsr = 0;
+
+ mutex_lock(&mdev_state->rxtx_lock);
+ /* atleast one char in FIFO */
+ if (mdev_state->s[index].rxtx.head !=
+ mdev_state->s[index].rxtx.tail)
+ lsr |= UART_LSR_DR;
+
+ /* if FIFO overrun */
+ if (mdev_state->s[index].overrun)
+ lsr |= UART_LSR_OE;
+
+ /* transmit FIFO empty and tramsitter empty */
+ if (mdev_state->s[index].rxtx.head ==
+ mdev_state->s[index].rxtx.tail)
+ lsr |= UART_LSR_TEMT | UART_LSR_THRE;
+
+ mutex_unlock(&mdev_state->rxtx_lock);
+ *buf = lsr;
+ break;
+ }
+ case UART_MSR:
+ *buf = UART_MSR_DSR | UART_MSR_DDSR | UART_MSR_DCD;
+
+ mutex_lock(&mdev_state->rxtx_lock);
+ /* if AFE is 1 and FIFO have space, set CTS bit */
+ if (mdev_state->s[index].uart_reg[UART_MCR] &
+ UART_MCR_AFE) {
+ if (mdev_state->s[index].rxtx.count <
+ mdev_state->s[index].max_fifo_size)
+ *buf |= UART_MSR_CTS | UART_MSR_DCTS;
+ } else
+ *buf |= UART_MSR_CTS | UART_MSR_DCTS;
+ mutex_unlock(&mdev_state->rxtx_lock);
+
+ break;
+
+ case UART_SCR:
+ *buf = mdev_state->s[index].uart_reg[offset];
+ break;
+
+ default:
+ break;
+ }
+}
+
+static void mdev_read_base(struct mdev_state *mdev_state)
+{
+ int index, pos;
+ u32 start_lo, start_hi;
+ u32 mem_type;
+
+ pos = PCI_BASE_ADDRESS_0;
+
+ for (index = 0; index <= VFIO_PCI_BAR5_REGION_INDEX; index++) {
+
+ if (!mdev_state->region_info[index].size)
+ continue;
+
+ start_lo = (*(u32 *)(mdev_state->vconfig + pos)) &
+ PCI_BASE_ADDRESS_MEM_MASK;
+ mem_type = (*(u32 *)(mdev_state->vconfig + pos)) &
+ PCI_BASE_ADDRESS_MEM_TYPE_MASK;
+
+ switch (mem_type) {
+ case PCI_BASE_ADDRESS_MEM_TYPE_64:
+ start_hi = (*(u32 *)(mdev_state->vconfig + pos + 4));
+ pos += 4;
+ break;
+ case PCI_BASE_ADDRESS_MEM_TYPE_32:
+ case PCI_BASE_ADDRESS_MEM_TYPE_1M:
+ /* 1M mem BAR treated as 32-bit BAR */
+ default:
+ /* mem unknown type treated as 32-bit BAR */
+ start_hi = 0;
+ break;
+ }
+ pos += 4;
+ mdev_state->region_info[index].start = ((u64)start_hi << 32) |
+ start_lo;
+ }
+}
+
+static ssize_t mdev_access(struct mdev_device *mdev, char *buf,
+ size_t count, loff_t pos, bool is_write)
+{
+ struct mdev_state *mdev_state;
+ unsigned int index;
+ loff_t offset;
+ int ret = 0;
+
+ if (!mdev || !buf)
+ return -EINVAL;
+
+ mdev_state = mdev_get_drvdata(mdev);
+ if (!mdev_state) {
+ pr_err("%s mdev_state not found\n", __func__);
+ return -EINVAL;
+ }
+
+ mutex_lock(&mdev_state->ops_lock);
+
+ index = MTTY_VFIO_PCI_OFFSET_TO_INDEX(pos);
+ offset = pos & MTTY_VFIO_PCI_OFFSET_MASK;
+ switch (index) {
+ case VFIO_PCI_CONFIG_REGION_INDEX:
+
+#if defined(DEBUG)
+ pr_info("%s: PCI config space %s at offset 0x%llx\n",
+ __func__, is_write ? "write" : "read", offset);
+#endif
+ if (is_write) {
+ dump_buffer(buf, count);
+ handle_pci_cfg_write(mdev_state, offset, buf, count);
+ } else {
+ memcpy(buf, (mdev_state->vconfig + offset), count);
+ dump_buffer(buf, count);
+ }
+
+ break;
+
+ case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
+ if (!mdev_state->region_info[index].start)
+ mdev_read_base(mdev_state);
+
+ if (is_write) {
+ dump_buffer(buf, count);
+
+#if defined(DEBUG_REGS)
+ pr_info("%s: BAR%d WR @0x%llx %s val:0x%02x dlab:%d\n",
+ __func__, index, offset, wr_reg[offset],
+ (u8)*buf, mdev_state->s[index].dlab);
+#endif
+ handle_bar_write(index, mdev_state, offset, buf, count);
+ } else {
+ handle_bar_read(index, mdev_state, offset, buf, count);
+ dump_buffer(buf, count);
+
+#if defined(DEBUG_REGS)
+ pr_info("%s: BAR%d RD @0x%llx %s val:0x%02x dlab:%d\n",
+ __func__, index, offset, rd_reg[offset],
+ (u8)*buf, mdev_state->s[index].dlab);
+#endif
+ }
+ break;
+
+ default:
+ ret = -1;
+ goto accessfailed;
+ }
+
+ ret = count;
+
+
+accessfailed:
+ mutex_unlock(&mdev_state->ops_lock);
+
+ return ret;
+}
+
+int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
+{
+ struct mdev_state *mdev_state;
+
+ if (!mdev)
+ return -EINVAL;
+
+ mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
+ if (mdev_state == NULL)
+ return -ENOMEM;
+
+ mdev_state->irq_index = -1;
+ mdev_state->s[0].max_fifo_size = MAX_FIFO_SIZE;
+ mdev_state->s[1].max_fifo_size = MAX_FIFO_SIZE;
+ mutex_init(&mdev_state->rxtx_lock);
+ mdev_state->vconfig = kzalloc(MTTY_CONFIG_SPACE_SIZE, GFP_KERNEL);
+
+ if (mdev_state->vconfig == NULL) {
+ kfree(mdev_state);
+ return -ENOMEM;
+ }
+
+ mutex_init(&mdev_state->ops_lock);
+ mdev_state->mdev = mdev;
+ mdev_set_drvdata(mdev, mdev_state);
+
+ mtty_create_config_space(mdev_state);
+
+ mutex_lock(&mdev_list_lock);
+ list_add(&mdev_state->next, &mdev_devices_list);
+ mutex_unlock(&mdev_list_lock);
+
+ return 0;
+}
+
+int mtty_remove(struct mdev_device *mdev)
+{
+ struct mdev_state *mds, *tmp_mds;
+ struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+ int ret = -EINVAL;
+
+ mutex_lock(&mdev_list_lock);
+ list_for_each_entry_safe(mds, tmp_mds, &mdev_devices_list, next) {
+ if (mdev_state == mds) {
+ list_del(&mdev_state->next);
+ mdev_set_drvdata(mdev, NULL);
+ kfree(mdev_state->vconfig);
+ kfree(mdev_state);
+ ret = 0;
+ break;
+ }
+ }
+ mutex_unlock(&mdev_list_lock);
+
+ return ret;
+}
+
+int mtty_reset(struct mdev_device *mdev)
+{
+ struct mdev_state *mdev_state;
+
+ if (!mdev)
+ return -EINVAL;
+
+ mdev_state = mdev_get_drvdata(mdev);
+ if (!mdev_state)
+ return -EINVAL;
+
+ pr_info("%s: called\n", __func__);
+
+ return 0;
+}
+
+ssize_t mtty_read(struct mdev_device *mdev, char *buf,
+ size_t count, loff_t pos)
+{
+ return mdev_access(mdev, buf, count, pos, false);
+}
+
+ssize_t mtty_write(struct mdev_device *mdev, char *buf,
+ size_t count, loff_t pos)
+{
+ return mdev_access(mdev, buf, count, pos, true);
+}
+
+static int mtty_set_irqs(struct mdev_device *mdev, uint32_t flags,
+ unsigned int index, unsigned int start,
+ unsigned int count, void *data)
+{
+ int ret = 0;
+ struct mdev_state *mdev_state;
+
+ if (!mdev)
+ return -EINVAL;
+
+ mdev_state = mdev_get_drvdata(mdev);
+ if (!mdev_state)
+ return -EINVAL;
+
+ mutex_lock(&mdev_state->ops_lock);
+ switch (index) {
+ case VFIO_PCI_INTX_IRQ_INDEX:
+ switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
+ case VFIO_IRQ_SET_ACTION_MASK:
+ case VFIO_IRQ_SET_ACTION_UNMASK:
+ break;
+ case VFIO_IRQ_SET_ACTION_TRIGGER:
+ {
+ if (flags & VFIO_IRQ_SET_DATA_NONE) {
+ pr_info("%s: disable INTx\n", __func__);
+ break;
+ }
+
+ if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+ int fd = *(int *)data;
+
+ if (fd > 0) {
+ struct fd irqfd;
+
+ irqfd = fdget(fd);
+ if (!irqfd.file) {
+ ret = -EBADF;
+ break;
+ }
+ mdev_state->intx_file = irqfd.file;
+ fdput(irqfd);
+ mdev_state->irq_fd = fd;
+ mdev_state->irq_index = index;
+ break;
+ }
+ }
+ break;
+ }
+ }
+ break;
+ case VFIO_PCI_MSI_IRQ_INDEX:
+ switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
+ case VFIO_IRQ_SET_ACTION_MASK:
+ case VFIO_IRQ_SET_ACTION_UNMASK:
+ break;
+ case VFIO_IRQ_SET_ACTION_TRIGGER:
+ if (flags & VFIO_IRQ_SET_DATA_NONE) {
+ pr_info("%s: disable MSI\n", __func__);
+ mdev_state->irq_index = VFIO_PCI_INTX_IRQ_INDEX;
+ break;
+ }
+ if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+ int fd = *(int *)data;
+ struct fd irqfd;
+
+ if (fd <= 0)
+ break;
+
+ if (mdev_state->msi_file)
+ break;
+
+ irqfd = fdget(fd);
+ if (!irqfd.file) {
+ ret = -EBADF;
+ break;
+ }
+
+ mdev_state->msi_file = irqfd.file;
+ fdput(irqfd);
+ mdev_state->irq_fd = fd;
+ mdev_state->irq_index = index;
+ }
+ break;
+ }
+ break;
+ case VFIO_PCI_MSIX_IRQ_INDEX:
+ pr_info("%s: MSIX_IRQ\n", __func__);
+ break;
+ case VFIO_PCI_ERR_IRQ_INDEX:
+ pr_info("%s: ERR_IRQ\n", __func__);
+ break;
+ case VFIO_PCI_REQ_IRQ_INDEX:
+ pr_info("%s: REQ_IRQ\n", __func__);
+ break;
+ }
+
+ mutex_unlock(&mdev_state->ops_lock);
+ return ret;
+}
+
+static int mtty_trigger_interrupt(uuid_le uuid)
+{
+ mm_segment_t old_fs;
+ u64 val = 1;
+ loff_t offset = 0;
+ int ret = -1;
+ struct file *pfile = NULL;
+ struct mdev_state *mdev_state;
+
+ mdev_state = find_mdev_state_by_uuid(uuid);
+
+ if (!mdev_state) {
+ pr_info("%s: mdev not found\n", __func__);
+ return -EINVAL;
+ }
+
+ if ((mdev_state->irq_index == VFIO_PCI_MSI_IRQ_INDEX) &&
+ (mdev_state->msi_file == NULL))
+ return -EINVAL;
+ else if ((mdev_state->irq_index == VFIO_PCI_INTX_IRQ_INDEX) &&
+ (mdev_state->intx_file == NULL)) {
+ pr_info("%s: Intr file not found\n", __func__);
+ return -EINVAL;
+ }
+
+ old_fs = get_fs();
+ set_fs(KERNEL_DS);
+
+ if (mdev_state->irq_index == VFIO_PCI_MSI_IRQ_INDEX)
+ pfile = mdev_state->msi_file;
+ else
+ pfile = mdev_state->intx_file;
+
+ if (pfile && pfile->f_op && pfile->f_op->write) {
+ ret = pfile->f_op->write(pfile, (char *)&val, sizeof(val),
+ &offset);
+#if defined(DEBUG_INTR)
+ pr_info("Intx triggered\n");
+#endif
+ } else
+ pr_err("%s: pfile not valid, intr_type = %d\n", __func__,
+ mdev_state->irq_index);
+
+ set_fs(old_fs);
+
+ if (ret < 0)
+ pr_err("%s: eventfd write failed (%d)\n", __func__, ret);
+
+ return ret;
+}
+
+int mtty_get_region_info(struct mdev_device *mdev,
+ struct vfio_region_info *region_info,
+ u16 *cap_type_id, void **cap_type)
+{
+ unsigned int size = 0;
+ struct mdev_state *mdev_state;
+ int bar_index;
+
+ if (!mdev)
+ return -EINVAL;
+
+ mdev_state = mdev_get_drvdata(mdev);
+ if (!mdev_state)
+ return -EINVAL;
+
+ mutex_lock(&mdev_state->ops_lock);
+ bar_index = region_info->index;
+
+ switch (bar_index) {
+ case VFIO_PCI_CONFIG_REGION_INDEX:
+ size = MTTY_CONFIG_SPACE_SIZE;
+ break;
+ case VFIO_PCI_BAR0_REGION_INDEX:
+ size = MTTY_IO_BAR_SIZE;
+ break;
+ case VFIO_PCI_BAR1_REGION_INDEX:
+ size = MTTY_IO_BAR_SIZE;
+ break;
+ default:
+ size = 0;
+ break;
+ }
+
+ mdev_state->region_info[bar_index].size = size;
+ mdev_state->region_info[bar_index].vfio_offset =
+ MTTY_VFIO_PCI_INDEX_TO_OFFSET(bar_index);
+
+ region_info->size = size;
+ region_info->offset = MTTY_VFIO_PCI_INDEX_TO_OFFSET(bar_index);
+ region_info->flags = VFIO_REGION_INFO_FLAG_READ |
+ VFIO_REGION_INFO_FLAG_WRITE;
+ mutex_unlock(&mdev_state->ops_lock);
+ return 0;
+}
+
+int mtty_get_irq_info(struct mdev_device *mdev, struct vfio_irq_info *irq_info)
+{
+ switch (irq_info->index) {
+ case VFIO_PCI_INTX_IRQ_INDEX:
+ case VFIO_PCI_MSI_IRQ_INDEX:
+ case VFIO_PCI_REQ_IRQ_INDEX:
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ irq_info->flags = VFIO_IRQ_INFO_EVENTFD;
+ irq_info->count = 1;
+
+ if (irq_info->index == VFIO_PCI_INTX_IRQ_INDEX)
+ irq_info->flags |= (VFIO_IRQ_INFO_MASKABLE |
+ VFIO_IRQ_INFO_AUTOMASKED);
+ else
+ irq_info->flags |= VFIO_IRQ_INFO_NORESIZE;
+
+ return 0;
+}
+
+int mtty_get_device_info(struct mdev_device *mdev,
+ struct vfio_device_info *dev_info)
+{
+ dev_info->flags = VFIO_DEVICE_FLAGS_PCI;
+ dev_info->num_regions = VFIO_PCI_NUM_REGIONS;
+ dev_info->num_irqs = VFIO_PCI_NUM_IRQS;
+
+ return 0;
+}
+
+static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
+ unsigned long arg)
+{
+ int ret = 0;
+ unsigned long minsz;
+ struct mdev_state *mdev_state;
+
+ if (!mdev)
+ return -EINVAL;
+
+ mdev_state = mdev_get_drvdata(mdev);
+ if (!mdev_state)
+ return -ENODEV;
+
+ switch (cmd) {
+ case VFIO_DEVICE_GET_INFO:
+ {
+ struct vfio_device_info info;
+
+ minsz = offsetofend(struct vfio_device_info, num_irqs);
+
+ if (copy_from_user(&info, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (info.argsz < minsz)
+ return -EINVAL;
+
+ ret = mtty_get_device_info(mdev, &info);
+ if (ret)
+ return ret;
+
+ memcpy(&mdev_state->dev_info, &info, sizeof(info));
+
+ return copy_to_user((void __user *)arg, &info, minsz);
+ }
+ case VFIO_DEVICE_GET_REGION_INFO:
+ {
+ struct vfio_region_info info;
+ struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+ u16 cap_type_id = 0;
+ void *cap_type = NULL;
+
+ minsz = offsetofend(struct vfio_region_info, offset);
+
+ if (copy_from_user(&info, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (info.argsz < minsz)
+ return -EINVAL;
+
+ ret = mtty_get_region_info(mdev, &info, &cap_type_id,
+ &cap_type);
+ if (ret)
+ return ret;
+
+ ret = vfio_info_add_capability(&info, &caps, cap_type_id,
+ cap_type);
+ if (ret)
+ return ret;
+
+ if (info.cap_offset) {
+ if (copy_to_user((void __user *)arg + info.cap_offset,
+ caps.buf, caps.size)) {
+ kfree(caps.buf);
+ return -EFAULT;
+ }
+ kfree(caps.buf);
+ }
+
+ return copy_to_user((void __user *)arg, &info, minsz);
+ }
+
+ case VFIO_DEVICE_GET_IRQ_INFO:
+ {
+ struct vfio_irq_info info;
+
+ minsz = offsetofend(struct vfio_irq_info, count);
+
+ if (copy_from_user(&info, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if ((info.argsz < minsz) ||
+ (info.index >= mdev_state->dev_info.num_irqs))
+ return -EINVAL;
+
+ ret = mtty_get_irq_info(mdev, &info);
+ if (ret)
+ return ret;
+
+ if (info.count == -1)
+ return -EINVAL;
+
+ return copy_to_user((void __user *)arg, &info, minsz);
+ }
+ case VFIO_DEVICE_SET_IRQS:
+ {
+ struct vfio_irq_set hdr;
+ u8 *data = NULL, *ptr = NULL;
+ int data_size = 0;
+
+ minsz = offsetofend(struct vfio_irq_set, count);
+
+ if (copy_from_user(&hdr, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ ret = vfio_set_irqs_validate_and_prepare(&hdr,
+ mdev_state->dev_info.num_irqs,
+ &data_size);
+ if (ret)
+ return ret;
+
+ if (data_size) {
+ ptr = data = memdup_user((void __user *)(arg + minsz),
+ data_size);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+ }
+
+ ret = mtty_set_irqs(mdev, hdr.flags, hdr.index, hdr.start,
+ hdr.count, data);
+
+ kfree(ptr);
+ return ret;
+ }
+ case VFIO_DEVICE_RESET:
+ return mtty_reset(mdev);
+ }
+ return -ENOTTY;
+}
+
+int mtty_open(struct mdev_device *mdev)
+{
+ pr_info("%s\n", __func__);
+ return 0;
+}
+
+void mtty_close(struct mdev_device *mdev)
+{
+ pr_info("%s\n", __func__);
+}
+
+static ssize_t
+sample_mtty_dev_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "This is phy device\n");
+}
+
+static DEVICE_ATTR_RO(sample_mtty_dev);
+
+static struct attribute *mtty_dev_attrs[] = {
+ &dev_attr_sample_mtty_dev.attr,
+ NULL,
+};
+
+static const struct attribute_group mtty_dev_group = {
+ .name = "mtty_dev",
+ .attrs = mtty_dev_attrs,
+};
+
+const struct attribute_group *mtty_dev_groups[] = {
+ &mtty_dev_group,
+ NULL,
+};
+
+static ssize_t
+sample_mdev_dev_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct mdev_device *mdev = to_mdev_device(dev);
+
+ if (mdev)
+ return sprintf(buf, "This is MDEV %s\n", dev_name(&mdev->dev));
+
+ return sprintf(buf, "\n");
+}
+
+static DEVICE_ATTR_RO(sample_mdev_dev);
+
+static struct attribute *mdev_dev_attrs[] = {
+ &dev_attr_sample_mdev_dev.attr,
+ NULL,
+};
+
+static const struct attribute_group mdev_dev_group = {
+ .name = "vendor",
+ .attrs = mdev_dev_attrs,
+};
+
+const struct attribute_group *mdev_dev_groups[] = {
+ &mdev_dev_group,
+ NULL,
+};
+
+static ssize_t
+name_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+ return sprintf(buf, "Dual-port-serial\n");
+}
+
+MDEV_TYPE_ATTR_RO(name);
+
+static ssize_t
+available_instances_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+ return sprintf(buf, "1\n");
+}
+
+MDEV_TYPE_ATTR_RO(available_instances);
+
+static struct attribute *mdev_types_attrs[] = {
+ &mdev_type_attr_name.attr,
+ &mdev_type_attr_available_instances.attr,
+ NULL,
+};
+
+static struct attribute_group mdev_type_group = {
+ .name = "mtty1",
+ .attrs = mdev_types_attrs,
+};
+
+struct attribute_group *mdev_type_groups[] = {
+ &mdev_type_group,
+ NULL,
+};
+
+struct parent_ops mdev_fops = {
+ .owner = THIS_MODULE,
+ .dev_attr_groups = mtty_dev_groups,
+ .mdev_attr_groups = mdev_dev_groups,
+ .supported_type_groups = mdev_type_groups,
+ .create = mtty_create,
+ .remove = mtty_remove,
+ .open = mtty_open,
+ .release = mtty_close,
+ .read = mtty_read,
+ .write = mtty_write,
+ .ioctl = mtty_ioctl,
+};
+
+static void mtty_device_release(struct device *dev)
+{
+ dev_dbg(dev, "mtty: released\n");
+}
+
+static int __init mtty_dev_init(void)
+{
+ int ret = 0;
+
+ pr_info("mtty_dev: %s\n", __func__);
+
+ memset(&mtty_dev, 0, sizeof(mtty_dev));
+
+ idr_init(&mtty_dev.vd_idr);
+
+ ret = alloc_chrdev_region(&mtty_dev.vd_devt, 0, MINORMASK, MTTY_NAME);
+
+ if (ret < 0) {
+ pr_err("Error: failed to register mtty_dev, err:%d\n", ret);
+ return ret;
+ }
+
+ cdev_init(&mtty_dev.vd_cdev, &vd_fops);
+ cdev_add(&mtty_dev.vd_cdev, mtty_dev.vd_devt, MINORMASK);
+
+ pr_info("major_number:%d\n", MAJOR(mtty_dev.vd_devt));
+
+ mtty_dev.vd_class = class_create(THIS_MODULE, MTTY_CLASS_NAME);
+
+ if (IS_ERR(mtty_dev.vd_class)) {
+ pr_err("Error: failed to register mtty_dev class\n");
+ goto failed1;
+ }
+
+ mtty_dev.dev.release = mtty_device_release;
+ dev_set_name(&mtty_dev.dev, "%s", MTTY_NAME);
+
+ ret = device_register(&mtty_dev.dev);
+ if (ret)
+ goto failed2;
+
+ if (mdev_register_device(&mtty_dev.dev, &mdev_fops) != 0)
+ goto failed3;
+
+ mutex_init(&mdev_list_lock);
+ INIT_LIST_HEAD(&mdev_devices_list);
+
+ goto all_done;
+
+failed3:
+
+ device_unregister(&mtty_dev.dev);
+failed2:
+ class_destroy(mtty_dev.vd_class);
+
+failed1:
+ cdev_del(&mtty_dev.vd_cdev);
+ unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+
+all_done:
+ return ret;
+}
+
+static void __exit mtty_dev_exit(void)
+{
+ mtty_dev.dev.bus = NULL;
+ mdev_unregister_device(&mtty_dev.dev);
+
+ device_unregister(&mtty_dev.dev);
+ idr_destroy(&mtty_dev.vd_idr);
+ cdev_del(&mtty_dev.vd_cdev);
+ unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+ class_destroy(mtty_dev.vd_class);
+ mtty_dev.vd_class = NULL;
+ pr_info("mtty_dev: Unloaded!\n");
+}
+
+module_init(mtty_dev_init)
+module_exit(mtty_dev_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_INFO(supported, "Test driver that simulate serial port over PCI");
+MODULE_VERSION(VERSION_STRING);
+MODULE_AUTHOR(DRIVER_AUTHOR);
diff --git a/Documentation/vfio-mdev/vfio-mediated-device.txt b/Documentation/vfio-mdev/vfio-mediated-device.txt
index c1eacb83807b..2b23b4d431a3 100644
--- a/Documentation/vfio-mdev/vfio-mediated-device.txt
+++ b/Documentation/vfio-mdev/vfio-mediated-device.txt
@@ -209,6 +209,69 @@ supported in TYPE1 IOMMU module. To enable the same for other IOMMU backend
modules, such as PPC64 sPAPR module, they need to provide these two callback
functions.

+Sample code
+-----------
+File mtty.c in this folder is a sample code to demonstrate how to use mediated
+device framework.
+
+Sample driver creates mdev device that simulates serial port over PCI card.
+
+Build and load mtty.ko module. This creates a dummy device, /sys/devices/mtty
+Files in this device directory in sysfs looks like:
+
+# ls /sys/devices/mtty/ -l
+total 0
+drwxr-xr-x 2 root root 0 Sep 29 12:34 mdev_supported_types
+drwxr-xr-x 2 root root 0 Sep 29 12:34 mtty_dev
+drwxr-xr-x 2 root root 0 Sep 29 12:34 power
+-rw-r--r-- 1 root root 4096 Sep 29 12:34 uevent
+
+Create mediated device using this device:
+# echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" > \
+ /sys/devices/mtty/mdev_supported_types/mtty1/create
+
+Add parameters to qemu-kvm:
+-device vfio-pci,\
+ sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
+
+Boot the VM. In Linux guest (no hardware in host), device is seen as below:
+
+# lspci -s 00:05.0 -xxvv
+00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])
+ Subsystem: Device 4348:3253
+ Physical Slot: 5
+ Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
+Stepping- SERR- FastB2B- DisINTx-
+ Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-
+<TAbort- <MAbort- >SERR- <PERR- INTx-
+ Interrupt: pin A routed to IRQ 10
+ Region 0: I/O ports at c150 [size=8]
+ Region 1: I/O ports at c158 [size=8]
+ Kernel driver in use: serial
+00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00
+10: 51 c1 00 00 59 c1 00 00 00 00 00 00 00 00 00 00
+20: 00 00 00 00 00 00 00 00 00 00 00 00 48 43 53 32
+30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 00 00
+
+In guest dmesg:
+serial 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ 10
+0000:00:05.0: ttyS1 at I/O 0xc150 (irq = 10) is a 16550A
+0000:00:05.0: ttyS2 at I/O 0xc158 (irq = 10) is a 16550A
+
+Check the serial ports in guest:
+# setserial -g /dev/ttyS*
+/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
+/dev/ttyS1, UART: 16550A, Port: 0xc150, IRQ: 10
+/dev/ttyS2, UART: 16550A, Port: 0xc158, IRQ: 10
+
+Using minicom or any terminal enulation program, open port /dev/ttyS1 or
+/dev/ttyS2 with hardware flow control disabled. Type data on minicom terminal or
+send data to terminal emulation program and read tha data. Data is loop backed
+from hosts mtty driver.
+
+Destroy mediated device created above by:
+# echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001/remove
+
References
----------

--
2.7.0