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* [PATCH v2] vdpa: Allow VDPA to work on big-endian machine
@ 2025-06-16 13:36 Konstantin Shkolnyy
  2025-06-21  5:52 ` Akihiko Odaki
  0 siblings, 1 reply; 8+ messages in thread
From: Konstantin Shkolnyy @ 2025-06-16 13:36 UTC (permalink / raw)
  To: jasowang, akihiko.odaki, yin31149
  Cc: qemu-devel, mjrosato, Konstantin Shkolnyy, Eugenio Pérez

After commit 0caed25cd171 vhost_vdpa_net_load_vlan() started seeing
VIRTIO_NET_F_CTRL_VLAN flag and making 4096 calls to the kernel with
VIRTIO_NET_CTRL_VLAN_ADD command. However, it forgot to convert the
16-bit VLAN IDs to LE format. On BE machine, the kernel calls failed
when they saw "VLAN IDs" greater than 4095, and QEMU then said:
"unable to start vhost net: 5: falling back on userspace virtio", and
VDPA became disabled.

Convert the VLAN ID to LE before putting it into virtio queue.

Fixes: 8f7e9967484d ("vdpa: Restore vlan filtering state")
Signed-off-by: Konstantin Shkolnyy <kshk@linux.ibm.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
---
Changes in v2:
 - Replace __le16 with uint16_t.
 - Add "Fixes:" tag.

 net/vhost-vdpa.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 58d738945d..bd5c37305d 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -1173,9 +1173,10 @@ static int vhost_vdpa_net_load_single_vlan(VhostVDPAState *s,
                                            struct iovec *in_cursor,
                                            uint16_t vid)
 {
+    uint16_t vid_le = cpu_to_le16(vid);
     const struct iovec data = {
-        .iov_base = &vid,
-        .iov_len = sizeof(vid),
+        .iov_base = &vid_le,
+        .iov_len = sizeof(vid_le),
     };
     ssize_t r = vhost_vdpa_net_load_cmd(s, out_cursor, in_cursor,
                                         VIRTIO_NET_CTRL_VLAN,
-- 
2.34.1



^ permalink raw reply related	[flat|nested] 8+ messages in thread
* [PATCH v2] vdpa: Allow vDPA to work on big-endian machine
@ 2025-02-21 19:07 Konstantin Shkolnyy
  2025-02-24  1:57 ` Jason Wang
  2025-03-14 11:36 ` Eugenio Perez Martin
  0 siblings, 2 replies; 8+ messages in thread
From: Konstantin Shkolnyy @ 2025-02-21 19:07 UTC (permalink / raw)
  To: jasowang, mst
  Cc: eperezma, sgarzare, mjrosato, qemu-devel, Konstantin Shkolnyy

Add .set_vnet_le() function that always returns success, assuming that
vDPA h/w always implements LE data format. Otherwise, QEMU disables vDPA and
outputs the message:
"backend does not support LE vnet headers; falling back on userspace virtio"

Signed-off-by: Konstantin Shkolnyy <kshk@linux.ibm.com>
---
Changes in V2: Add code comment.

 net/vhost-vdpa.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 231b45246c..6e7cec4d45 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -270,6 +270,18 @@ static bool vhost_vdpa_has_ufo(NetClientState *nc)
 
 }
 
+/*
+ * FIXME: vhost_vdpa doesn't have an API to "set h/w endianness". But it's
+ * reasonable to assume that h/w is LE by default, because LE is what
+ * virtio 1.0 and later ask for. So, this function just says "yes, the h/w is
+ * LE". Otherwise, on a BE machine, higher-level code would mistakely think
+ * the h/w is BE and can't support VDPA for a virtio 1.0 client.
+ */
+static int vhost_vdpa_set_vnet_le(NetClientState *nc, bool enable)
+{
+    return 0;
+}
+
 static bool vhost_vdpa_check_peer_type(NetClientState *nc, ObjectClass *oc,
                                        Error **errp)
 {
@@ -437,6 +449,7 @@ static NetClientInfo net_vhost_vdpa_info = {
         .cleanup = vhost_vdpa_cleanup,
         .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
         .has_ufo = vhost_vdpa_has_ufo,
+        .set_vnet_le = vhost_vdpa_set_vnet_le,
         .check_peer_type = vhost_vdpa_check_peer_type,
         .set_steering_ebpf = vhost_vdpa_set_steering_ebpf,
 };
-- 
2.34.1



^ permalink raw reply related	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2025-06-21  5:53 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-06-16 13:36 [PATCH v2] vdpa: Allow VDPA to work on big-endian machine Konstantin Shkolnyy
2025-06-21  5:52 ` Akihiko Odaki
  -- strict thread matches above, loose matches on Subject: below --
2025-02-21 19:07 [PATCH v2] vdpa: Allow vDPA " Konstantin Shkolnyy
2025-02-24  1:57 ` Jason Wang
2025-03-13 15:13   ` Konstantin Shkolnyy
2025-03-17  0:26     ` Jason Wang
2025-03-17  0:36       ` Michael S. Tsirkin
2025-03-14 11:36 ` Eugenio Perez Martin

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