On 2/12/2025 12:07, Philippe Mathieu-Daudé wrote:
On 12/2/25 18:24, Konstantin Shkolnyy wrote:
On 2/12/2025 08:52, Philippe Mathieu-Daudé wrote:
On 11/2/25 17:19, Konstantin Shkolnyy wrote:
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 <k...@linux.ibm.com>
---
net/vhost-vdpa.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 231b45246c..7219aa2eee 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -270,6 +270,11 @@ static bool vhost_vdpa_has_ufo(NetClientState *nc)
}
+static int vhost_vdpa_set_vnet_le(NetClientState *nc, bool is_le)
+{
+ return 0;
+}
+
static bool vhost_vdpa_check_peer_type(NetClientState *nc,
ObjectClass *oc,
Error **errp)
{
@@ -437,6 +442,7 @@ 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,
Dubious mismatch with set_vnet_be handler.
I'm not sure what you are suggesting...
Implement set_vnet_le for parity?
To my (very limited) knowledge, kernel's vhost_vdpa that QEMU talks to
doesn't have an API to "change h/w endianness". If so, vDPA's
.set_vnet_le/be(), as well as qemu_set_vnet_le/be() have very limited
choices. qemu_set_vnet_le/be() behavior with vDPA was to simply assume
that h/w endianness by default matches host's. This assumption is valid
for other types of "NetClients" which are implemented in s/w. However, I
suspect, vDPA h/w might all be going to be LE, to match virtio 1.0. Such
is the NIC I'm dealing with.
My patch is only fixing a specific use case. Perhaps, for a complete
fix, qemu_set_vnet_be() also shouldn't unconditionally return success on
big endian machines, but always call .set_vnet_be() so that vDPA could
fail it? But then it would start calling .set_vnet_be() on other
"NetClients" where it didn't before.
That's why I don't want to just add a .set_vnet_be(), before someone
here even confirms that vDPA h/w is indeed assumed LE, and, hence, what
the right path is to a complete solution...
int qemu_set_vnet_be(NetClientState *nc, bool is_be)
{
#if HOST_BIG_ENDIAN
return 0;
#else
if (!nc || !nc->info->set_vnet_be)
return -ENOSYS;
return nc->info->set_vnet_be(nc, is_be);
#endif
}
