[Qemu-devel] [RFC]virtio-blk: add disk-name device property

[Junkang Fu]

>From 74e913fc41ea98d1dde692175f1e3fb6729342aa Mon Sep 17 00:00:00 2001
From: "junkang.fjk" <address@hidden>
Date: Wed, 24 Aug 2016 19:36:53 +0800
Subject: [PATCH] virtio-blk: add disk-name device property

Current virtio-blk disk name(ex. /dev/vdb) has nothing to do with the
target dev
name specified in libvirt xml file. For example, we may get disk name
/dev/vdb in
VM while target dev specified in libvirt xml is vdc. This may lead to a
little trouble
to find out the relationship between the disk name in VM and somewhere out
of
VM, for example in the control board of Public cloud service providers. I
suggest
if Qemu could add a VIRTIO_BLK_F_DISK_NAME feature, with
VIRTIO_BLK_F_DISK_NAME
capable Qemu and virtio-blk frontend drivers, disk name in the vm can be
specified
as follows:
        -device virtio-blk-pci,disk-name=vdabc

---
 hw/block/virtio-blk.c                       | 5 +++++
 include/hw/virtio/virtio-blk.h              | 1 +
 include/standard-headers/linux/virtio_blk.h | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 331d766..4039fb9 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -716,6 +716,8 @@ static void virtio_blk_update_config(VirtIODevice
*vdev, uint8_t *config)
     blkcfg.alignment_offset = 0;
     blkcfg.wce = blk_enable_write_cache(s->blk);
     virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
+    if (s->disk_name)
+        strncpy((char *)blkcfg.disk_name, s->disk_name, DISK_NAME_LEN);
     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 }
@@ -740,6 +742,8 @@ static uint64_t virtio_blk_get_features(VirtIODevice
*vdev, uint64_t features,
     virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
     virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
     virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
+    virtio_add_feature(&features, VIRTIO_BLK_F_DISK_NAME);
+
     if (virtio_has_feature(features, VIRTIO_F_VERSION_1)) {
         if (s->conf.scsi) {
             error_setg(errp, "Please set scsi=off for virtio-blk devices
in order to use virtio 1.0");
@@ -970,6 +974,7 @@ static Property virtio_blk_properties[] = {
     DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging,
0,
                     true),
     DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
+    DEFINE_PROP_STRING("disk-name", VirtIOBlock, disk_name),
     DEFINE_PROP_END_OF_LIST(),
 };

diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 180bd8d..003e810 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -56,6 +56,7 @@ typedef struct VirtIOBlock {
     bool dataplane_disabled;
     bool dataplane_started;
     struct VirtIOBlockDataPlane *dataplane;
+    char *disk_name;
 } VirtIOBlock;

 typedef struct VirtIOBlockReq {
diff --git a/include/standard-headers/linux/virtio_blk.h
b/include/standard-headers/linux/virtio_blk.h
index ab16ec5..1f5d89d 100644
--- a/include/standard-headers/linux/virtio_blk.h
+++ b/include/standard-headers/linux/virtio_blk.h
@@ -38,6 +38,7 @@
 #define VIRTIO_BLK_F_BLK_SIZE  6   /* Block size of disk is available*/
 #define VIRTIO_BLK_F_TOPOLOGY  10  /* Topology information is available */
 #define VIRTIO_BLK_F_MQ        12  /* support more than one vq */
+#define VIRTIO_BLK_F_DISK_NAME  13      /* specify /dev/xxx name */

 /* Legacy feature bits */
 #ifndef VIRTIO_BLK_NO_LEGACY
@@ -51,6 +52,9 @@

 #define VIRTIO_BLK_ID_BYTES    20  /* ID string length */

+/* micro defined in kernel genhd.h */
+#define DISK_NAME_LEN 32
+
 struct virtio_blk_config {
    /* The capacity (in 512-byte sectors). */
    uint64_t capacity;
@@ -84,6 +88,8 @@ struct virtio_blk_config {

    /* number of vqs, only available when VIRTIO_BLK_F_MQ is set */
    uint16_t num_queues;
+
+   uint8_t disk_name[DISK_NAME_LEN];
 } QEMU_PACKED;

 /*
--
1.9.4

0001-virtio-blk-add-disk-name-device-property.patch
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