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Re: [PATCH 5/7] vhost: Distinguish errors in vhost_dev_get_config()

From: Stefano Garzarella
Subject: Re: [PATCH 5/7] vhost: Distinguish errors in vhost_dev_get_config()
Date: Thu, 10 Jun 2021 11:16:20 +0200 
On Wed, Jun 09, 2021 at 05:46:56PM +0200, Kevin Wolf wrote:

Instead of just returning 0/-1 and letting the caller make up a
meaningless error message, add an Error parameter to allow reporting the
real error and switch to 0/-errno so that different kind of errors can
be distinguished in the caller.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
include/hw/virtio/vhost-backend.h |  2 +-
include/hw/virtio/vhost.h         |  4 ++--
hw/block/vhost-user-blk.c         |  9 +++++----
hw/display/vhost-user-gpu.c       |  6 ++++--
hw/input/vhost-user-input.c       |  6 ++++--
hw/net/vhost_net.c                |  2 +-
hw/virtio/vhost-user-vsock.c      |  9 +++++----
hw/virtio/vhost-user.c            | 24 ++++++++++++------------
hw/virtio/vhost-vdpa.c            |  2 +-
hw/virtio/vhost.c                 | 14 +++++++++++---
10 files changed, 46 insertions(+), 32 deletions(-)

diff --git a/include/hw/virtio/vhost-backend.h 
b/include/hw/virtio/vhost-backend.h
index 728ebb0ed9..8475c5a29d 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -98,7 +98,7 @@ typedef int (*vhost_set_config_op)(struct vhost_dev *dev, 
const uint8_t *data,
                                   uint32_t offset, uint32_t size,
                                   uint32_t flags);
typedef int (*vhost_get_config_op)(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len);
+                                   uint32_t config_len, Error **errp);

typedef int (*vhost_crypto_create_session_op)(struct vhost_dev *dev,
                                              void *session_info,
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 2d7aaad67b..045d0fd9f2 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -130,8 +130,8 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
                          struct vhost_vring_file *file);

int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
-int vhost_dev_get_config(struct vhost_dev *dev, uint8_t *config,
-                         uint32_t config_len);
+int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
+                         uint32_t config_len, Error **errp);
int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
                         uint32_t offset, uint32_t size, uint32_t flags);
/* notifier callback in case vhost device config space changed
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index e9382e152a..3770f715da 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -91,11 +91,13 @@ static int vhost_user_blk_handle_config_change(struct 
vhost_dev *dev)
    int ret;
    struct virtio_blk_config blkcfg;
    VHostUserBlk *s = VHOST_USER_BLK(dev->vdev);
+    Error *local_err = NULL;

    ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
-                               sizeof(struct virtio_blk_config));
+                               sizeof(struct virtio_blk_config),
+                               &local_err);
    if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
        return -1;
    }

@@ -478,9 +480,8 @@ static void vhost_user_blk_device_realize(DeviceState *dev, 
Error **errp)
    assert(s->connected);

    ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
-                               sizeof(struct virtio_blk_config));
+                               sizeof(struct virtio_blk_config), errp);
    if (ret < 0) {
-        error_setg(errp, "vhost-user-blk: get block config failed");
        goto vhost_err;
    }

diff --git a/hw/display/vhost-user-gpu.c b/hw/display/vhost-user-gpu.c
index 6cdaa1c73b..389199e6ca 100644
--- a/hw/display/vhost-user-gpu.c
+++ b/hw/display/vhost-user-gpu.c
@@ -415,14 +415,16 @@ vhost_user_gpu_get_config(VirtIODevice *vdev, uint8_t 
*config_data)
    VirtIOGPUBase *b = VIRTIO_GPU_BASE(vdev);
    struct virtio_gpu_config *vgconfig =
        (struct virtio_gpu_config *)config_data;
+    Error *local_err = NULL;
    int ret;

    memset(config_data, 0, sizeof(struct virtio_gpu_config));

    ret = vhost_dev_get_config(&g->vhost->dev,
-                               config_data, sizeof(struct virtio_gpu_config));
+                               config_data, sizeof(struct virtio_gpu_config),
+                               &local_err);
    if (ret) {
-        error_report("vhost-user-gpu: get device config space failed");
+        error_report_err(local_err);
        return;
    }

diff --git a/hw/input/vhost-user-input.c b/hw/input/vhost-user-input.c
index 63984a8ba7..273e96a7b1 100644
--- a/hw/input/vhost-user-input.c
+++ b/hw/input/vhost-user-input.c
@@ -49,13 +49,15 @@ static void vhost_input_get_config(VirtIODevice *vdev, 
uint8_t *config_data)
{
    VirtIOInput *vinput = VIRTIO_INPUT(vdev);
    VHostUserInput *vhi = VHOST_USER_INPUT(vdev);
+    Error *local_err = NULL;
    int ret;

    memset(config_data, 0, vinput->cfg_size);

-    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, 
vinput->cfg_size);
+    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, vinput->cfg_size,
+                               &local_err);
    if (ret) {
-        error_report("vhost-user-input: get device config space failed");
+        error_report_err(local_err);
        return;
    }
}
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 447b119f85..10a7780a13 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -117,7 +117,7 @@ uint64_t vhost_net_get_features(struct vhost_net *net, 
uint64_t features)
int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
                         uint32_t config_len)
{
-    return vhost_dev_get_config(&net->dev, config, config_len);
+    return vhost_dev_get_config(&net->dev, config, config_len, NULL);
}
int vhost_net_set_config(struct vhost_net *net, const uint8_t *data,
                         uint32_t offset, uint32_t size, uint32_t flags)
diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
index b6a4a25ea1..6095ed7349 100644
--- a/hw/virtio/vhost-user-vsock.c
+++ b/hw/virtio/vhost-user-vsock.c
@@ -34,10 +34,12 @@ static void vuv_get_config(VirtIODevice *vdev, uint8_t 
*config)
static int vuv_handle_config_change(struct vhost_dev *dev)
{
    VHostUserVSock *vsock = VHOST_USER_VSOCK(dev->vdev);
+    Error *local_err = NULL;
    int ret = vhost_dev_get_config(dev, (uint8_t *)&vsock->vsockcfg,
-                                   sizeof(struct virtio_vsock_config));
+                                   sizeof(struct virtio_vsock_config),
+                                   &local_err);
    if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
        return -1;
    }

@@ -114,9 +116,8 @@ static void vuv_device_realize(DeviceState *dev, Error 
**errp)
    }

    ret = vhost_dev_get_config(&vvc->vhost_dev, (uint8_t *)&vsock->vsockcfg,
-                               sizeof(struct virtio_vsock_config));
+                               sizeof(struct virtio_vsock_config), errp);
    if (ret < 0) {
-        error_setg_errno(errp, -ret, "get config space failed");
        goto err_vhost_dev;
    }

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 889559d86a..1ac4a2ebec 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2117,7 +2117,7 @@ static void vhost_user_set_iotlb_callback(struct 
vhost_dev *dev, int enabled)
}

static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
-                                 uint32_t config_len)
+                                 uint32_t config_len, Error **errp)
{
    VhostUserMsg msg = {
        .hdr.request = VHOST_USER_GET_CONFIG,
@@ -2127,32 +2127,32 @@ static int vhost_user_get_config(struct vhost_dev *dev, 
uint8_t *config,

    if (!virtio_has_feature(dev->protocol_features,
                VHOST_USER_PROTOCOL_F_CONFIG)) {
-        return -1;
+        error_setg(errp, "VHOST_USER_PROTOCOL_F_CONFIG not supported");
+        return -EINVAL;
    }

-    if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
-        return -1;
-    }
+    assert(config_len <= VHOST_USER_MAX_CONFIG_SIZE);

    msg.payload.config.offset = 0;
    msg.payload.config.size = config_len;
    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
    }

    if (vhost_user_read(dev, &msg) < 0) {
-        return -1;
+        return -EPROTO;
    }

    if (msg.hdr.request != VHOST_USER_GET_CONFIG) {
-        error_report("Received unexpected msg type. Expected %d received %d",
-                     VHOST_USER_GET_CONFIG, msg.hdr.request);
-        return -1;
+        error_setg(errp,
+                   "Received unexpected msg type. Expected %d received %d",
+                   VHOST_USER_GET_CONFIG, msg.hdr.request);
+        return -EINVAL;
    }

    if (msg.hdr.size != VHOST_USER_CONFIG_HDR_SIZE + config_len) {
-        error_report("Received bad msg size.");
-        return -1;
+        error_setg(errp, "Received bad msg size.");
+        return -EINVAL;
    }

    memcpy(config, msg.payload.config.region, config_len);
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 71897c1a01..6b6f974a83 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -451,7 +451,7 @@ static int vhost_vdpa_set_config(struct vhost_dev *dev, 
const uint8_t *data,
}

static int vhost_vdpa_get_config(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len)
+                                   uint32_t config_len, Error **errp)
{
    struct vhost_vdpa_config *v_config;
    unsigned long config_size = offsetof(struct vhost_vdpa_config, buf);
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index c7f9d8bb06..1b66f1de70 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1562,15 +1562,23 @@ void vhost_ack_features(struct vhost_dev *hdev, const 
int *feature_bits,
}

int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
-                         uint32_t config_len)
+                         uint32_t config_len, Error **errp)
{
+    ERRP_GUARD();
+    int ret;
+
    assert(hdev->vhost_ops);

    if (hdev->vhost_ops->vhost_get_config) {
-        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len);
+        ret = hdev->vhost_ops->vhost_get_config(hdev, config, config_len, 
errp);
+        if (ret < 0 && !*errp) {
+            error_setg_errno(errp, -ret, "vhost_get_config failed");
+        }
+        return ret;
    }

-    return -1;
+    error_setg(errp, "vhost_dev_get_config not implemented");

                        ^
Maybe I'd replace s/vhost_dev_get_config/vhost_get_config

But it's not that important:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
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