vduse: Support specifying bounce buffer size via sysfs

As discussed in [1], this adds sysfs interface to support
specifying bounce buffer size in virtio-vdpa case. It would
be a performance tuning parameter for high throughput workloads.

[1] https://lore.kernel.org/netdev/e8f25a35-9d45-69f9-795d-bdbbb90337a3@redhat.com/

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230323053043.35-12-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index ccca84d51a28a9526a730a5fa99171d188547d6b..34eebdf030af7984aef80d946ff1dd99634d5272 100644 (file)
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -37,8 +37,11 @@
 #define DRV_LICENSE  "GPL v2"
 
 #define VDUSE_DEV_MAX (1U << MINORBITS)
+#define VDUSE_MAX_BOUNCE_SIZE (1024 * 1024 * 1024)
+#define VDUSE_MIN_BOUNCE_SIZE (1024 * 1024)
 #define VDUSE_BOUNCE_SIZE (64 * 1024 * 1024)
-#define VDUSE_IOVA_SIZE (128 * 1024 * 1024)
+/* 128 MB reserved for virtqueue creation */
+#define VDUSE_IOVA_SIZE (VDUSE_MAX_BOUNCE_SIZE + 128 * 1024 * 1024)
 #define VDUSE_MSG_DEFAULT_TIMEOUT 30
 
 #define IRQ_UNBOUND -1
@@ -1715,8 +1718,48 @@ static ssize_t msg_timeout_store(struct device *device,
 
 static DEVICE_ATTR_RW(msg_timeout);
 
+static ssize_t bounce_size_show(struct device *device,
+                               struct device_attribute *attr, char *buf)
+{
+       struct vduse_dev *dev = dev_get_drvdata(device);
+
+       return sysfs_emit(buf, "%u\n", dev->bounce_size);
+}
+
+static ssize_t bounce_size_store(struct device *device,
+                                struct device_attribute *attr,
+                                const char *buf, size_t count)
+{
+       struct vduse_dev *dev = dev_get_drvdata(device);
+       unsigned int bounce_size;
+       int ret;
+
+       ret = -EPERM;
+       mutex_lock(&dev->domain_lock);
+       if (dev->domain)
+               goto unlock;
+
+       ret = kstrtouint(buf, 10, &bounce_size);
+       if (ret < 0)
+               goto unlock;
+
+       ret = -EINVAL;
+       if (bounce_size > VDUSE_MAX_BOUNCE_SIZE ||
+           bounce_size < VDUSE_MIN_BOUNCE_SIZE)
+               goto unlock;
+
+       dev->bounce_size = bounce_size & PAGE_MASK;
+       ret = count;
+unlock:
+       mutex_unlock(&dev->domain_lock);
+       return ret;
+}
+
+static DEVICE_ATTR_RW(bounce_size);
+
 static struct attribute *vduse_dev_attrs[] = {
        &dev_attr_msg_timeout.attr,
+       &dev_attr_bounce_size.attr,
        NULL
 };