From 8a08b3b41400e152cc1786ae5a8a53507f8e925c Mon Sep 17 00:00:00 2001
From: Jinhua Cao <caojinhua1@huawei.com>
Date: Thu, 10 Feb 2022 14:16:17 +0800
Subject: [PATCH] virtio: print the guest virtio_net features that host does
 not support

Signed-off-by: Jinhua Cao <caojinhua1@huawei.com>
---
 hw/net/virtio-net.c        | 41 ++++++++++++++++++++++++++++++++++++++
 hw/virtio/virtio.c         |  7 +++++++
 include/hw/virtio/virtio.h |  1 +
 3 files changed, 49 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index b3a5d0b19e..6874c88bc0 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3692,6 +3692,46 @@ static Property virtio_net_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static void virtio_net_print_features(uint64_t features)
+{
+    Property *props = virtio_net_properties;
+    int feature_cnt = 0;
+
+    if (!features) {
+        return;
+    }
+    printf("virtio_net_feature: ");
+
+    for (; features && props->name; props++) {
+        /* The bitnr of property may be default(0) besides 'csum' property. */
+        if (props->bitnr == 0 && strcmp(props->name, "csum")) {
+            continue;
+        }
+
+        /* Features only support 64bit. */
+        if (props->bitnr > 63) {
+            continue;
+        }
+
+        if (virtio_has_feature(features, props->bitnr)) {
+            virtio_clear_feature(&features, props->bitnr);
+            if (feature_cnt != 0) {
+                printf(", ");
+            }
+            printf("%s", props->name);
+            feature_cnt++;
+        }
+    }
+
+    if (features) {
+        if (feature_cnt != 0) {
+            printf(", ");
+        }
+        printf("unkown bits 0x%." PRIx64, features);
+    }
+    printf("\n");
+}
+
 static void virtio_net_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -3706,6 +3746,7 @@ static void virtio_net_class_init(ObjectClass *klass, void *data)
     vdc->set_config = virtio_net_set_config;
     vdc->get_features = virtio_net_get_features;
     vdc->set_features = virtio_net_set_features;
+    vdc->print_features = virtio_net_print_features;
     vdc->bad_features = virtio_net_bad_features;
     vdc->reset = virtio_net_reset;
     vdc->set_status = virtio_net_set_status;
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 0af9684881..9a2a83d507 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2967,6 +2967,13 @@ static int virtio_set_features_nocheck(VirtIODevice *vdev, uint64_t val)
 {
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
     bool bad = (val & ~(vdev->host_features)) != 0;
+    uint64_t feat = val & ~(vdev->host_features);
+
+    if (bad && k->print_features) {
+	qemu_log("error: Please check host config, "\
+		 "because host does not support required feature bits 0x%" PRIx64 "\n", feat);
+        k->print_features(feat);
+    }
 
     val &= vdev->host_features;
     if (k->set_features) {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index b3749ce34b..7472145821 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -127,6 +127,7 @@ struct VirtioDeviceClass {
     int (*validate_features)(VirtIODevice *vdev);
     void (*get_config)(VirtIODevice *vdev, uint8_t *config);
     void (*set_config)(VirtIODevice *vdev, const uint8_t *config);
+    void (*print_features)(uint64_t features);
     void (*reset)(VirtIODevice *vdev);
     void (*set_status)(VirtIODevice *vdev, uint8_t val);
     /* For transitional devices, this is a bitmap of features
-- 
2.27.0