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Re: [libvirt PATCH] Adds e1000e/vmxnet3 Vnet_hdr suuport



On 8/7/20 3:46 PM, Patrick J. Magauran wrote:
On Fri, 2020-08-07 at 17:16 +0100, Daniel P. Berrangé wrote:
On Thu, Aug 06, 2020 at 10:53:32PM -0400, Patrick Magauran wrote:
Libvirt bases its decision about whether to apply the vnet_hdr flag
to the tap interface on whether or not the selected model is
VirtIO. Originally, VirtIO was the only model to support the
vnet_hdr in QEMU; however, the e1000e & vmxnet3 adapters also
support it(seemingly from introduction based on commits). This
passes the whole packet to the host, reducing emulation overhead
and improving performance.

Signed-off-by: Patrick Magauran <patmagauran j gmail com>
---
  src/conf/domain_conf.c    | 8 +++++++-
  src/conf/domain_conf.h    | 1 +
  src/libvirt_private.syms  | 1 +
  src/qemu/qemu_interface.c | 8 ++++----
  4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 69e0439e7e..cb184110f7 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -30981,7 +30981,13 @@ virDomainNetIsVirtioModel(const
virDomainNetDef *net)
              net->model == VIR_DOMAIN_NET_MODEL_VIRTIO_TRANSITIONAL
||
              net->model ==
VIR_DOMAIN_NET_MODEL_VIRTIO_NON_TRANSITIONAL);
  }
-
+bool
+virDomainNetIsVnetCompatModel(const virDomainNetDef *net)
+{
+    return (virDomainNetIsVirtioModel(net) ||
+            net->model == VIR_DOMAIN_NET_MODEL_E1000E ||
+            net->model == VIR_DOMAIN_NET_MODEL_VMXNET3);
+}
Should really live in the qemu_inteface.c file,  with
a qemuOnterfaceIsVnetCompatModel name, since the decision
is inherantly tied to QEMU, and inappropriate for other
virt drivers.


Regards,
Daniel
I would think the qemu_interface.c file is more for the actual setup
functionality rather than simple helper functions. Would the
qemu_domain.c file make for sense?


If it's network interface specific and also qemu specific, then it should go into qemu_interface.c. That file didn't use to exist (all the functions there were just included in qemu_command.c) but was created as a place to split out all the interface-specific stuff (not just the toplevel "setup this kind of interface" functions).


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