diff --git a/docs/specs/pci-testdev.txt b/docs/specs/pci-testdev.txt
new file mode 100644
index 0000000..128ae22
--- /dev/null
+++ b/docs/specs/pci-testdev.txt
@@ -0,0 +1,26 @@
+pci-test is a device used for testing low level IO
+
+device implements up to two BARs: BAR0 and BAR1.
+Each BAR can be memory or IO. Guests must detect
+BAR type and act accordingly.
+
+Each BAR size is up to 4K bytes.
+Each BAR starts with the following header:
+
+typedef struct PCITestDevHdr {
+    uint8_t test;  <- write-only, starts a given test number
+    uint8_t width_type; <- read-only, type and width of access for a given test.
+                           1,2,4 for byte,word or long write.
+                           any other value if test not supported on this BAR
+    uint8_t pad0[2];
+    uint32_t offset; <- read-only, offset in this BAR for a given test
+    uint32_t data;    <- read-only, data to use for a given test
+    uint32_t count;  <- for debugging. number of writes detected.
+    uint8_t name[]; <- for debugging. 0-terminated ASCII string.
+} PCITestDevHdr;
+
+All registers are little endian.
+
+device is expected to always implement tests 0 to N on each BAR, and to add new
+tests with higher numbers.  In this way a guest can scan test numbers until it
+detects an access type that it does not support on this BAR, then stop.
diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index eb7eb31..b4e3b1d 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -12,6 +12,7 @@ common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
 common-obj-$(CONFIG_VIRTIO) += virtio-bus.o
 common-obj-y += fw_cfg.o
 common-obj-$(CONFIG_PCI) += pci_bridge_dev.o
+common-obj-$(CONFIG_PCI) += pci-testdev.o
 common-obj-$(CONFIG_PCI) += ioh3420.o xio3130_upstream.o xio3130_downstream.o
 common-obj-$(CONFIG_PCI) += i82801b11.o
 common-obj-y += watchdog.o
diff --git a/hw/pci-testdev.c b/hw/pci-testdev.c
new file mode 100644
index 0000000..9486624
--- /dev/null
+++ b/hw/pci-testdev.c
@@ -0,0 +1,306 @@
+#include "hw/hw.h"
+#include "hw/pci/pci.h"
+#include "qemu/event_notifier.h"
+#include "qemu/osdep.h"
+
+typedef struct PCITestDevHdr {
+    uint8_t test;
+    uint8_t width;
+    uint8_t pad0[2];
+    uint32_t offset;
+    uint8_t data;
+    uint8_t pad1[3];
+    uint32_t count;
+    uint8_t name[];
+} PCITestDevHdr;
+
+typedef struct IOTest {
+    MemoryRegion *mr;
+    EventNotifier notifier;
+    bool hasnotifier;
+    unsigned size;
+    bool match_data;
+    PCITestDevHdr *hdr;
+    unsigned bufsize;
+} IOTest;
+
+#define IOTEST_DATAMATCH 0xFA
+#define IOTEST_NOMATCH   0xCE
+
+#define IOTEST_IOSIZE 128
+#define IOTEST_MEMSIZE 2048
+
+static const char *iotest_test[] = {
+    "no-eventfd",
+    "wildcard-eventfd",
+    "datamatch-eventfd"
+};
+
+static const char *iotest_type[] = {
+    "mmio",
+    "portio"
+};
+
+#define IOTEST_TEST(i) (iotest_test[((i) % ARRAY_SIZE(iotest_test))])
+#define IOTEST_TYPE(i) (iotest_type[((i) / ARRAY_SIZE(iotest_test))])
+#define IOTEST_MAX_TEST (ARRAY_SIZE(iotest_test))
+#define IOTEST_MAX_TYPE (ARRAY_SIZE(iotest_type))
+#define IOTEST_MAX (IOTEST_MAX_TEST * IOTEST_MAX_TYPE)
+
+enum {
+    IOTEST_ACCESS_NAME,
+    IOTEST_ACCESS_DATA,
+    IOTEST_ACCESS_MAX,
+};
+
+#define IOTEST_ACCESS_TYPE uint8_t
+#define IOTEST_ACCESS_WIDTH (sizeof(uint8_t))
+
+typedef struct PCITestDevState {
+    PCIDevice dev;
+    MemoryRegion mmio;
+    MemoryRegion portio;
+    IOTest *tests;
+    int current;
+} PCITestDevState;
+
+#define IOTEST_IS_MEM(i) (strcmp(IOTEST_TYPE(i), "portio"))
+#define IOTEST_REGION(d, i) (IOTEST_IS_MEM(i) ?  &(d)->mmio : &(d)->portio)
+#define IOTEST_SIZE(i) (IOTEST_IS_MEM(i) ? IOTEST_MEMSIZE : IOTEST_IOSIZE)
+#define IOTEST_PCI_BAR(i) (IOTEST_IS_MEM(i) ? PCI_BASE_ADDRESS_SPACE_MEMORY : \
+                           PCI_BASE_ADDRESS_SPACE_IO)
+
+static int pci_testdev_start(IOTest *test)
+{
+    test->hdr->count = 0;
+    if (!test->hasnotifier) {
+        return 0;
+    }
+    event_notifier_test_and_clear(&test->notifier);
+    memory_region_add_eventfd(test->mr,
+                              le32_to_cpu(test->hdr->offset),
+                              test->size,
+                              test->match_data,
+                              test->hdr->data,
+                              &test->notifier);
+    return 0;
+}
+
+static void pci_testdev_stop(IOTest *test)
+{
+    if (!test->hasnotifier) {
+        return;
+    }
+    memory_region_del_eventfd(test->mr,
+                              le32_to_cpu(test->hdr->offset),
+                              test->size,
+                              test->match_data,
+                              test->hdr->data,
+                              &test->notifier);
+}
+
+static void
+pci_testdev_reset(PCITestDevState *d)
+{
+    if (d->current == -1) {
+        return;
+    }
+    pci_testdev_stop(&d->tests[d->current]);
+    d->current = -1;
+}
+
+static void pci_testdev_inc(IOTest *test, unsigned inc)
+{
+    uint32_t c = le32_to_cpu(test->hdr->count);
+    test->hdr->count = cpu_to_le32(c + inc);
+}
+
+static void
+pci_testdev_write(void *opaque, hwaddr addr, uint64_t val,
+                  unsigned size, int type)
+{
+    PCITestDevState *d = opaque;
+    IOTest *test;
+    int t, r;
+
+    if (addr == offsetof(PCITestDevHdr, test)) {
+        pci_testdev_reset(d);
+        if (val >= IOTEST_MAX_TEST) {
+            return;
+        }
+        t = type * IOTEST_MAX_TEST + val;
+        r = pci_testdev_start(&d->tests[t]);
+        if (r < 0) {
+            return;
+        }
+        d->current = t;
+        return;
+    }
+    if (d->current < 0) {
+        return;
+    }
+    test = &d->tests[d->current];
+    if (addr != le32_to_cpu(test->hdr->offset)) {
+        return;
+    }
+    if (test->match_data && test->size != size) {
+        return;
+    }
+    if (test->match_data && val != test->hdr->data) {
+        return;
+    }
+    pci_testdev_inc(test, 1);
+}
+
+static uint64_t
+pci_testdev_read(void *opaque, hwaddr addr, unsigned size)
+{
+    PCITestDevState *d = opaque;
+    const char *buf;
+    IOTest *test;
+    if (d->current < 0) {
+        return 0;
+    }
+    test = &d->tests[d->current];
+    buf = (const char *)test->hdr;
+    if (addr + size >= test->bufsize) {
+        return 0;
+    }
+    if (test->hasnotifier) {
+        event_notifier_test_and_clear(&test->notifier);
+    }
+    return buf[addr];
+}
+
+static void
+pci_testdev_mmio_write(void *opaque, hwaddr addr, uint64_t val,
+                       unsigned size)
+{
+    pci_testdev_write(opaque, addr, val, size, 0);
+}
+
+static void
+pci_testdev_pio_write(void *opaque, hwaddr addr, uint64_t val,
+                       unsigned size)
+{
+    pci_testdev_write(opaque, addr, val, size, 1);
+}
+
+static const MemoryRegionOps pci_testdev_mmio_ops = {
+    .read = pci_testdev_read,
+    .write = pci_testdev_mmio_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
+};
+
+static const MemoryRegionOps pci_testdev_pio_ops = {
+    .read = pci_testdev_read,
+    .write = pci_testdev_pio_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
+};
+
+static int pci_testdev_init(PCIDevice *pci_dev)
+{
+    PCITestDevState *d = DO_UPCAST(PCITestDevState, dev, pci_dev);
+    uint8_t *pci_conf;
+    char *name;
+    int r, i;
+
+    pci_conf = d->dev.config;
+
+    pci_conf[PCI_INTERRUPT_PIN] = 0; /* no interrupt pin */
+
+    memory_region_init_io(&d->mmio, &pci_testdev_mmio_ops, d,
+                          "pci-testdev-mmio", IOTEST_MEMSIZE * 2);
+    memory_region_init_io(&d->portio, &pci_testdev_pio_ops, d,
+                          "pci-testdev-portio", IOTEST_IOSIZE * 2);
+    pci_register_bar(&d->dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY, &d->mmio);
+    pci_register_bar(&d->dev, 1, PCI_BASE_ADDRESS_SPACE_IO, &d->portio);
+
+    d->current = -1;
+    d->tests = g_malloc0(IOTEST_MAX * sizeof *d->tests);
+    for (i = 0; i < IOTEST_MAX; ++i) {
+        IOTest *test = &d->tests[i];
+        name = g_strdup_printf("%s-%s", IOTEST_TYPE(i), IOTEST_TEST(i));
+        test->bufsize = sizeof(PCITestDevHdr) + strlen(name) + 1;
+        test->hdr = g_malloc0(test->bufsize);
+        memcpy(test->hdr->name, name, strlen(name) + 1);
+        g_free(name);
+        test->hdr->offset = cpu_to_le32(IOTEST_SIZE(i) + i * IOTEST_ACCESS_WIDTH);
+        test->size = IOTEST_ACCESS_WIDTH;
+        test->match_data = strcmp(IOTEST_TEST(i), "wildcard-eventfd");
+        test->hdr->test = i;
+        test->hdr->data = test->match_data ? IOTEST_DATAMATCH : IOTEST_NOMATCH;
+        test->hdr->width = IOTEST_ACCESS_WIDTH;
+        test->mr = IOTEST_REGION(d, i);
+        if (!strcmp(IOTEST_TEST(i), "no-eventfd")) {
+            test->hasnotifier = false;
+            continue;
+        }
+        r = event_notifier_init(&test->notifier, 0);
+        assert(r >= 0);
+        test->hasnotifier = true;
+    }
+
+    return 0;
+}
+
+static void
+pci_testdev_uninit(PCIDevice *dev)
+{
+    PCITestDevState *d = DO_UPCAST(PCITestDevState, dev, dev);
+    int i;
+
+    pci_testdev_reset(d);
+    for (i = 0; i < IOTEST_MAX; ++i) {
+        if (d->tests[i].hasnotifier) {
+            event_notifier_cleanup(&d->tests[i].notifier);
+        }
+        g_free(d->tests[i].hdr);
+    }
+    g_free(d->tests);
+    memory_region_destroy(&d->mmio);
+    memory_region_destroy(&d->portio);
+}
+
+static void qdev_pci_testdev_reset(DeviceState *dev)
+{
+    PCITestDevState *d = DO_UPCAST(PCITestDevState, dev.qdev, dev);
+    pci_testdev_reset(d);
+}
+
+static void pci_testdev_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+
+    k->init = pci_testdev_init;
+    k->exit = pci_testdev_uninit;
+    k->vendor_id = PCI_VENDOR_ID_REDHAT;
+    k->device_id = PCI_DEVICE_ID_REDHAT_TEST;
+    k->revision = 0x00;
+    k->class_id = PCI_CLASS_OTHERS;
+    dc->desc = "PCI Test Device";
+    dc->reset = qdev_pci_testdev_reset;
+}
+
+static const TypeInfo pci_testdev_info = {
+    .name          = "pci-testdev",
+    .parent        = TYPE_PCI_DEVICE,
+    .instance_size = sizeof(PCITestDevState),
+    .class_init    = pci_testdev_class_init,
+};
+
+static void pci_testdev_register_types(void)
+{
+    type_register_static(&pci_testdev_info);
+}
+
+type_init(pci_testdev_register_types)
diff --git a/hw/pci/pci.h b/hw/pci/pci.h
index 774369c..d81198c 100644
--- a/hw/pci/pci.h
+++ b/hw/pci/pci.h
@@ -84,6 +84,7 @@
 #define PCI_DEVICE_ID_REDHAT_SERIAL      0x0002
 #define PCI_DEVICE_ID_REDHAT_SERIAL2     0x0003
 #define PCI_DEVICE_ID_REDHAT_SERIAL4     0x0004
+#define PCI_DEVICE_ID_REDHAT_TEST        0x0005
 #define PCI_DEVICE_ID_REDHAT_QXL         0x0100
 
 #define FMT_PCIBUS                      PRIx64
