[Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio

[Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio

[Shannon Zhao]

Add host/guest notifiers support for virtio-mmio, so that qemu can
enable vhost-net for kvm-arm.

Refer to the patches from Ying-Shiuan Pan
https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg00715.html

As vhost-net can improve the net performance by about 30%,
so I think it's necessary to make virtio-mmio work with vhost-net
on arm/arm64.

Shannon Zhao (4):
  virtio-mmio: introduce set_host_notifier()
  virtio-mmio: introduce set_guest_notifiers
  virtio-mmio: start ioeventfd when status gets DRIVER_OK
  virtio-mmio: add a new property for ioeventfd

 hw/net/virtio-net.c        |    1 +
 hw/virtio/virtio-mmio.c    |  176 ++++++++++++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h |    1 +
 3 files changed, 178 insertions(+), 0 deletions(-)

[Qemu-devel] [PATCH 1/4] virtio-mmio: introduce set_host_notifier()

[Shannon Zhao]

set_host_notifier() is introduced into virtio-mmio now. Most of codes came
from virtio-pci.

Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
Signed-off-by: Li Liu <john.liuli@huawei.com>
Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
---
 hw/virtio/virtio-mmio.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 70 insertions(+), 0 deletions(-)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 2450c13..d8ec2d1 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -23,6 +23,7 @@
 #include "hw/virtio/virtio.h"
 #include "qemu/host-utils.h"
 #include "hw/virtio/virtio-bus.h"
+#include "qemu/error-report.h"
 
 /* #define DEBUG_VIRTIO_MMIO */
 
@@ -87,8 +88,58 @@ typedef struct {
     uint32_t guest_page_shift;
     /* virtio-bus */
     VirtioBusState bus;
+    bool ioeventfd_disabled;
+    bool ioeventfd_started;
 } VirtIOMMIOProxy;
 
+static int virtio_mmio_set_host_notifier_internal(VirtIOMMIOProxy *proxy,
+                                                 int n, bool assign, bool set_handler)
+{
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+    VirtQueue *vq = virtio_get_queue(vdev, n);
+    EventNotifier *notifier = virtio_queue_get_host_notifier(vq);
+    int r = 0;
+
+    if (assign) {
+        r = event_notifier_init(notifier, 1);
+        if (r < 0) {
+            error_report("%s: unable to init event notifier: %d",
+                         __func__, r);
+            return r;
+        }
+        virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
+        memory_region_add_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
+                                  true, n, notifier);
+    } else {
+        memory_region_del_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
+                                  true, n, notifier);
+        virtio_queue_set_host_notifier_fd_handler(vq, false, false);
+        event_notifier_cleanup(notifier);
+    }
+    return r;
+}
+
+static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
+{
+    int r;
+    int n;
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+
+    if (!proxy->ioeventfd_started) {
+        return;
+    }
+
+    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+
+        r = virtio_mmio_set_host_notifier_internal(proxy, n, false, false);
+        assert(r >= 0);
+    }
+    proxy->ioeventfd_started = false;
+}
+
 static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
 {
     VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
@@ -342,6 +393,24 @@ static void virtio_mmio_reset(DeviceState *d)
     proxy->guest_page_shift = 0;
 }
 
+static int virtio_mmio_set_host_notifier(DeviceState *opaque, int n, bool assign)
+{
+    VirtIOMMIOProxy *proxy = VIRTIO_MMIO(opaque);
+
+    /* Stop using ioeventfd for virtqueue kick if the device starts using host
+     * notifiers.  This makes it easy to avoid stepping on each others' toes.
+     */
+    proxy->ioeventfd_disabled = assign;
+    if (assign) {
+        virtio_mmio_stop_ioeventfd(proxy);
+    }
+    /* We don't need to start here: it's not needed because backend
+     * currently only stops on status change away from ok,
+     * reset, vmstop and such. If we do add code to start here,
+     * need to check vmstate, device state etc. */
+    return virtio_mmio_set_host_notifier_internal(proxy, n, assign, false);
+}
+
 /* virtio-mmio device */
 
 /* This is called by virtio-bus just after the device is plugged. */
@@ -399,6 +468,7 @@ static void virtio_mmio_bus_class_init(ObjectClass *klass, void *data)
     k->notify = virtio_mmio_update_irq;
     k->save_config = virtio_mmio_save_config;
     k->load_config = virtio_mmio_load_config;
+    k->set_host_notifier = virtio_mmio_set_host_notifier;
     k->get_features = virtio_mmio_get_features;
     k->device_plugged = virtio_mmio_device_plugged;
     k->has_variable_vring_alignment = true;
-- 
1.7.1

Re: [Qemu-devel] [PATCH 1/4] virtio-mmio: introduce set_host_notifier()

[Fam Zheng]

On Tue, 11/04 20:47, Shannon Zhao wrote:
> set_host_notifier() is introduced into virtio-mmio now. Most of codes came
> from virtio-pci.
> 
> Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
> Signed-off-by: Li Liu <john.liuli@huawei.com>
> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
> ---
>  hw/virtio/virtio-mmio.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 70 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index 2450c13..d8ec2d1 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -23,6 +23,7 @@
>  #include "hw/virtio/virtio.h"
>  #include "qemu/host-utils.h"
>  #include "hw/virtio/virtio-bus.h"
> +#include "qemu/error-report.h"
>  
>  /* #define DEBUG_VIRTIO_MMIO */
>  
> @@ -87,8 +88,58 @@ typedef struct {
>      uint32_t guest_page_shift;
>      /* virtio-bus */
>      VirtioBusState bus;
> +    bool ioeventfd_disabled;
> +    bool ioeventfd_started;
>  } VirtIOMMIOProxy;
>  
> +static int virtio_mmio_set_host_notifier_internal(VirtIOMMIOProxy *proxy,
> +                                                 int n, bool assign, bool set_handler)

I didn't review the code, but checkpatch.pl noticed this line and one more
below [*] is too long (over 80 columes).

> +{
> +    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> +    VirtQueue *vq = virtio_get_queue(vdev, n);
> +    EventNotifier *notifier = virtio_queue_get_host_notifier(vq);
> +    int r = 0;
> +
> +    if (assign) {
> +        r = event_notifier_init(notifier, 1);
> +        if (r < 0) {
> +            error_report("%s: unable to init event notifier: %d",
> +                         __func__, r);
> +            return r;
> +        }
> +        virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
> +        memory_region_add_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
> +                                  true, n, notifier);
> +    } else {
> +        memory_region_del_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
> +                                  true, n, notifier);
> +        virtio_queue_set_host_notifier_fd_handler(vq, false, false);
> +        event_notifier_cleanup(notifier);
> +    }
> +    return r;
> +}
> +
> +static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
> +{
> +    int r;
> +    int n;
> +    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> +
> +    if (!proxy->ioeventfd_started) {
> +        return;
> +    }
> +
> +    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
> +        if (!virtio_queue_get_num(vdev, n)) {
> +            continue;
> +        }
> +
> +        r = virtio_mmio_set_host_notifier_internal(proxy, n, false, false);
> +        assert(r >= 0);
> +    }
> +    proxy->ioeventfd_started = false;
> +}
> +
>  static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
>  {
>      VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
> @@ -342,6 +393,24 @@ static void virtio_mmio_reset(DeviceState *d)
>      proxy->guest_page_shift = 0;
>  }
>  
> +static int virtio_mmio_set_host_notifier(DeviceState *opaque, int n, bool assign)

[*]

No need to respin yet just for this. Please wait for a serious review.

Thanks,

Fam

Re: [Qemu-devel] [PATCH 1/4] virtio-mmio: introduce set_host_notifier()

[Shannon Zhao]

On 2014/11/19 15:47, Fam Zheng wrote:
> On Tue, 11/04 20:47, Shannon Zhao wrote:
>> set_host_notifier() is introduced into virtio-mmio now. Most of codes came
>> from virtio-pci.
>>
>> Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
>> Signed-off-by: Li Liu <john.liuli@huawei.com>
>> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
>> ---
>>  hw/virtio/virtio-mmio.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 70 insertions(+), 0 deletions(-)
>>
>> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
>> index 2450c13..d8ec2d1 100644
>> --- a/hw/virtio/virtio-mmio.c
>> +++ b/hw/virtio/virtio-mmio.c
>> @@ -23,6 +23,7 @@
>>  #include "hw/virtio/virtio.h"
>>  #include "qemu/host-utils.h"
>>  #include "hw/virtio/virtio-bus.h"
>> +#include "qemu/error-report.h"
>>  
>>  /* #define DEBUG_VIRTIO_MMIO */
>>  
>> @@ -87,8 +88,58 @@ typedef struct {
>>      uint32_t guest_page_shift;
>>      /* virtio-bus */
>>      VirtioBusState bus;
>> +    bool ioeventfd_disabled;
>> +    bool ioeventfd_started;
>>  } VirtIOMMIOProxy;
>>  
>> +static int virtio_mmio_set_host_notifier_internal(VirtIOMMIOProxy *proxy,
>> +                                                 int n, bool assign, bool set_handler)
> 
> I didn't review the code, but checkpatch.pl noticed this line and one more
> below [*] is too long (over 80 columes).
> 
>> +{
>> +    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>> +    VirtQueue *vq = virtio_get_queue(vdev, n);
>> +    EventNotifier *notifier = virtio_queue_get_host_notifier(vq);
>> +    int r = 0;
>> +
>> +    if (assign) {
>> +        r = event_notifier_init(notifier, 1);
>> +        if (r < 0) {
>> +            error_report("%s: unable to init event notifier: %d",
>> +                         __func__, r);
>> +            return r;
>> +        }
>> +        virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
>> +        memory_region_add_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
>> +                                  true, n, notifier);
>> +    } else {
>> +        memory_region_del_eventfd(&proxy->iomem, VIRTIO_MMIO_QUEUENOTIFY, 4,
>> +                                  true, n, notifier);
>> +        virtio_queue_set_host_notifier_fd_handler(vq, false, false);
>> +        event_notifier_cleanup(notifier);
>> +    }
>> +    return r;
>> +}
>> +
>> +static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
>> +{
>> +    int r;
>> +    int n;
>> +    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>> +
>> +    if (!proxy->ioeventfd_started) {
>> +        return;
>> +    }
>> +
>> +    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
>> +        if (!virtio_queue_get_num(vdev, n)) {
>> +            continue;
>> +        }
>> +
>> +        r = virtio_mmio_set_host_notifier_internal(proxy, n, false, false);
>> +        assert(r >= 0);
>> +    }
>> +    proxy->ioeventfd_started = false;
>> +}
>> +
>>  static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
>>  {
>>      VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
>> @@ -342,6 +393,24 @@ static void virtio_mmio_reset(DeviceState *d)
>>      proxy->guest_page_shift = 0;
>>  }
>>  
>> +static int virtio_mmio_set_host_notifier(DeviceState *opaque, int n, bool assign)
> 
> [*]
> 
> No need to respin yet just for this. Please wait for a serious review.
> 

Ok,thanks,
Shannon

> Thanks,
> 
> Fam
> 
> .
> 


-- 
Shannon

[Qemu-devel] [PATCH 2/4] virtio-mmio: introduce set_guest_notifiers

[Shannon Zhao]

Same as host notifier of virtio-mmio, most of codes came from virtio-pci.
The kvm-arm does not yet support irqfd, need to fix the hard-coded part after
kvm-arm gets irqfd support.

Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
Signed-off-by: Li Liu <john.liuli@huawei.com>
Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
---
 hw/virtio/virtio-mmio.c |   60 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index d8ec2d1..b741f50 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -393,6 +393,65 @@ static void virtio_mmio_reset(DeviceState *d)
     proxy->guest_page_shift = 0;
 }
 
+static int virtio_mmio_set_guest_notifier(DeviceState *d, int n, bool assign,
+                                         bool with_irqfd)
+{
+    VirtIOMMIOProxy *proxy = VIRTIO_MMIO(d);
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+    VirtQueue *vq = virtio_get_queue(vdev, n);
+    EventNotifier *notifier = virtio_queue_get_guest_notifier(vq);
+
+    if (assign) {
+        int r = event_notifier_init(notifier, 0);
+        if (r < 0) {
+            return r;
+        }
+        virtio_queue_set_guest_notifier_fd_handler(vq, true, with_irqfd);
+    } else {
+        virtio_queue_set_guest_notifier_fd_handler(vq, false, with_irqfd);
+        event_notifier_cleanup(notifier);
+    }
+
+    if (vdc->guest_notifier_mask) {
+        vdc->guest_notifier_mask(vdev, n, !assign);
+    }
+
+    return 0;
+}
+
+static int virtio_mmio_set_guest_notifiers(DeviceState *d, int nvqs, bool assign)
+{
+    VirtIOMMIOProxy *proxy = VIRTIO_MMIO(d);
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+    /* TODO: need to check if kvm-arm supports irqfd */
+    bool with_irqfd = false;
+    int r, n;
+
+    nvqs = MIN(nvqs, VIRTIO_PCI_QUEUE_MAX);
+
+    for (n = 0; n < nvqs; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            break;
+        }
+
+        r = virtio_mmio_set_guest_notifier(d, n, assign, with_irqfd);
+        if (r < 0) {
+            goto assign_error;
+        }
+    }
+
+    return 0;
+
+assign_error:
+    /* We get here on assignment failure. Recover by undoing for VQs 0 .. n. */
+    assert(assign);
+    while (--n >= 0) {
+        virtio_mmio_set_guest_notifier(d, n, !assign, false);
+    }
+    return r;
+}
+
 static int virtio_mmio_set_host_notifier(DeviceState *opaque, int n, bool assign)
 {
     VirtIOMMIOProxy *proxy = VIRTIO_MMIO(opaque);
@@ -469,6 +528,7 @@ static void virtio_mmio_bus_class_init(ObjectClass *klass, void *data)
     k->save_config = virtio_mmio_save_config;
     k->load_config = virtio_mmio_load_config;
     k->set_host_notifier = virtio_mmio_set_host_notifier;
+    k->set_guest_notifiers = virtio_mmio_set_guest_notifiers;
     k->get_features = virtio_mmio_get_features;
     k->device_plugged = virtio_mmio_device_plugged;
     k->has_variable_vring_alignment = true;
-- 
1.7.1

[Qemu-devel] [PATCH 3/4] virtio-mmio: start ioeventfd when status gets DRIVER_OK

[Shannon Zhao]

Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
Signed-off-by: Li Liu <john.liuli@huawei.com>
Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
---
 hw/virtio/virtio-mmio.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 45 insertions(+), 0 deletions(-)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index b741f50..c543e71 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -119,6 +119,42 @@ static int virtio_mmio_set_host_notifier_internal(VirtIOMMIOProxy *proxy,
     return r;
 }
 
+static void virtio_mmio_start_ioeventfd(VirtIOMMIOProxy *proxy)
+{
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+    int n, r;
+
+    if (proxy->ioeventfd_disabled ||
+        proxy->ioeventfd_started) {
+        return;
+    }
+
+    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+
+        r = virtio_mmio_set_host_notifier_internal(proxy, n, true, true);
+        if (r < 0) {
+            goto assign_error;
+        }
+    }
+    proxy->ioeventfd_started = true;
+    return;
+
+assign_error:
+    while (--n >= 0) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+
+        r = virtio_mmio_set_host_notifier_internal(proxy, n, false, false);
+        assert(r >= 0);
+    }
+    proxy->ioeventfd_started = false;
+    error_report("%s: failed. Fallback to a userspace (slower).", __func__);
+}
+
 static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
 {
     int r;
@@ -317,7 +353,16 @@ static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
         virtio_update_irq(vdev);
         break;
     case VIRTIO_MMIO_STATUS:
+        if (!(value & VIRTIO_CONFIG_S_DRIVER_OK)) {
+            virtio_mmio_stop_ioeventfd(proxy);
+        }
+
         virtio_set_status(vdev, value & 0xff);
+
+        if (value & VIRTIO_CONFIG_S_DRIVER_OK) {
+            virtio_mmio_start_ioeventfd(proxy);
+        }
+
         if (vdev->status == 0) {
             virtio_reset(vdev);
         }
-- 
1.7.1

[Qemu-devel] [PATCH 4/4] virtio-mmio: add a new property for ioeventfd

[Shannon Zhao]

Make ioeventfd could be enabled or disabled (default). Since ioeventfd
is not yet ready in kvm-arm, without this option, qemu will get a
problem if it attempts to initialize ioeventfd.

Signed-off-by: Ying-Shiuan Pan <yingshiuan.pan@gmail.com>
Signed-off-by: Li Liu <john.liuli@huawei.com>
Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
---
 hw/net/virtio-net.c        |    1 +
 hw/virtio/virtio-mmio.c    |    3 ++-
 include/hw/virtio/virtio.h |    1 +
 3 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 9b88775..d89d4a6 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1723,6 +1723,7 @@ static Property virtio_net_properties[] = {
                                                TX_TIMER_INTERVAL),
     DEFINE_PROP_INT32("x-txburst", VirtIONet, net_conf.txburst, TX_BURST),
     DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx),
+    DEFINE_PROP_BOOL("ioeventfd", VirtIONet, parent_obj.use_ioeventfd, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index c543e71..16697ed 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -124,7 +124,8 @@ static void virtio_mmio_start_ioeventfd(VirtIOMMIOProxy *proxy)
     VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
     int n, r;
 
-    if (proxy->ioeventfd_disabled ||
+    if (!vdev->use_ioeventfd ||
+        proxy->ioeventfd_disabled ||
         proxy->ioeventfd_started) {
         return;
     }
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 0726d76..e4bc8ad 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -127,6 +127,7 @@ struct VirtIODevice
     bool vm_running;
     VMChangeStateEntry *vmstate;
     char *bus_name;
+    bool use_ioeventfd;
     uint8_t device_endian;
 };
 
-- 
1.7.1

Re: [Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio

[Shannon Zhao]

On 2014/11/4 20:47, Shannon Zhao wrote:
> Add host/guest notifiers support for virtio-mmio, so that qemu can
> enable vhost-net for kvm-arm.
> 
> Refer to the patches from Ying-Shiuan Pan
> https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg00715.html
> 
> As vhost-net can improve the net performance by about 30%,
> so I think it's necessary to make virtio-mmio work with vhost-net
> on arm/arm64.
Hi,

Some virtio-net with virtio-mmio performance data on ARM added as followed:

Type of backend         bandwith(GBytes/sec) (From Host to Guest)
virtio-net              0.66
vhost-net               1.49
vhost-net with irqfd    2.01

Test cmd: ./iperf -c 192.168.0.2 -P 1 -i 10 -p 5001 -f G -t 60

>From this test data, vhost-net and irqfd have great improvement on performance.
So maybe it's necessary to enable ioeventfd make vhost-net work with
virtio-mmio on ARM/ARM64.

Look forward to your feedback :)

Thanks,
Shannon

> 
> Shannon Zhao (4):
>   virtio-mmio: introduce set_host_notifier()
>   virtio-mmio: introduce set_guest_notifiers
>   virtio-mmio: start ioeventfd when status gets DRIVER_OK
>   virtio-mmio: add a new property for ioeventfd
> 
>  hw/net/virtio-net.c        |    1 +
>  hw/virtio/virtio-mmio.c    |  176 ++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/virtio/virtio.h |    1 +
>  3 files changed, 178 insertions(+), 0 deletions(-)
> 
> 
> 

-- 
Shannon

Re: [Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio

[Paolo Bonzini]

On 04/11/2014 13:47, Shannon Zhao wrote:
> Add host/guest notifiers support for virtio-mmio, so that qemu can
> enable vhost-net for kvm-arm.
> 
> Refer to the patches from Ying-Shiuan Pan
> https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg00715.html
> 
> As vhost-net can improve the net performance by about 30%,
> so I think it's necessary to make virtio-mmio work with vhost-net
> on arm/arm64.
> 
> Shannon Zhao (4):
>   virtio-mmio: introduce set_host_notifier()
>   virtio-mmio: introduce set_guest_notifiers
>   virtio-mmio: start ioeventfd when status gets DRIVER_OK
>   virtio-mmio: add a new property for ioeventfd
> 
>  hw/net/virtio-net.c        |    1 +
>  hw/virtio/virtio-mmio.c    |  176 ++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/virtio/virtio.h |    1 +
>  3 files changed, 178 insertions(+), 0 deletions(-)
> 
> 
> 

Peter/Michael, could you review this series for 2.3?

Paolo

[Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio

[Ying-Shiuan Pan]

I added host/guest notifiers support for virtio-mmio, so that qemu can
enable vhost-net for kvm-arm. Sorry for that I cannot measure the performance
difference because I have only Exynos-5250 arndale boards which only provide
a 100 Mbps Ethernet. But in our previous work in kvm-arm (refer: Evaluation of
a Server-Grade Software-Only ARM Hypervisor), the vhost-net increased at least
30% in throughput comparing to virtio-net.

Ying-Shiuan Pan (4):
  virtio-mmio: introduce set_host_notifier()
  virtio-mmio: introduce set_guest_notifiers
  virtio-mmio: start ioeventfd when status gets DRIVER_OK
  virtio-mmio: add a new property for ioeventfd

 hw/block/virtio-blk.c      |   1 +
 hw/net/virtio-net.c        |   1 +
 hw/virtio/virtio-mmio.c    | 176 +++++++++++++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h |   1 +
 4 files changed, 179 insertions(+)

-- 
1.8.1.2