CVS commit: src/sys/dev/pci

["Ryota Ozaki" <ozaki-r%netbsd.org@localhost>]

Module Name:    src
Committed By:   ozaki-r
Date:           Fri Dec 19 06:54:40 UTC 2014

Modified Files:
        src/sys/dev/pci: if_vioif.c virtio.c virtiovar.h

Log Message:
Implement softint-based interrupt handling in if_vioif

Softint-based interrupt handling is considered as a future direction
of the (network) device driver architecture in NetBSD. pq3etsec of
ppc is already implemented based on the architecture (unlike pq3etsec,
this change doesn't include softint-based if_start). In this
architecture, a hardware interrupt handler just schedules a softint
and the softint performs actual interrupt processing. It reduces
processing in hardware interrupt context and allows Layer 2 network
stack (e.g., bridge, vlan and even bpf) run in softint context,
which makes it easy to implement fine-grain locking in the layer.

This is an experimental implementation of the architecture in if_viof.

virtio introduces a new flag VIRTIO_F_PCI_INTR_SOFTINT. If a driver
of virtio sets it to sc_flags of virtio_softc, virtio calls
softint_schedule in virtio_intr instead of directly calling the
interrupt handler of the driver.

When VIOIF_SOFTINT_INTR is on, vioif doesn't use the existing softint
(vioif_rx_softint) that is called from vioif_rx_vq_done. Because
vioif_rx_softint already runs in softint context and another softint
isn't needed. This change actually improves performance in some cases.

The feature is disabled by default and enabled when SOFTINT_INTR is
set somewhere (normally in a kernel configuration).


To generate a diff of this commit:
cvs rdiff -u -r1.11 -r1.12 src/sys/dev/pci/if_vioif.c
cvs rdiff -u -r1.7 -r1.8 src/sys/dev/pci/virtio.c
cvs rdiff -u -r1.3 -r1.4 src/sys/dev/pci/virtiovar.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.