v1:
1. fix some small problems
2. remove commit "virtio_net: introduce vi->mode"
In the last linux version, we disabled this feature to fix the
regress[1].
The patch set is try to fix the problem and re-enable it.
More info:
http://lore.kernel.org/all/20240820071913.68004-1-xuanz...@lin
When the frag just got a page, then may lead to regression on VM.
Specially if the sysctl net.core.high_order_alloc_disable value is 1,
then the frag always get a page when do refill.
Which could see reliable crashes or scp failure (scp a file 100M in size
to VM).
The issue is that the virtnet_rq
Now, the premapped mode can be enabled unconditionally.
So we can remove the failover code for merge and small mode.
The virtnet_rq_xxx() helper would be only used if the mode is using pre
mapping. A check is added to prevent misusing of these API.
Tested-by: Darren Kenny
Signed-off-by: Xuan Zh
Currently, the virtio core will perform a dma operation for each
buffer. Although, the same page may be operated multiple times.
In premapped mod, we can perform only one dma operation for the pages of
the alloc frag. This is beneficial for the iommu device.
kernel command line: intel_iommu=on io
The virtio-net big mode did not enable premapped mode,
so we did not need to check the unmap. And the subsequent
commit will remove the failover code for failing enable
premapped for merge and small mode. So we need to remove
the checking do_dma code in the big mode path.
Tested-by: Darren Kenny
