[V3,0/6] IRQ offloading for vDPA

Message

Zhu, Lingshan July 22, 2020, 10:08 a.m. UTC

This series intends to implement IRQ offloading for
vhost_vdpa.

By the feat of irq forwarding facilities like posted
interrupt on X86, irq bypass can  help deliver
interrupts to vCPU directly.

vDPA devices have dedicated hardware backends like VFIO
pass-throughed devices. So it would be possible to setup
irq offloading(irq bypass) for vDPA devices and gain
performance improvements.

In my testing, with this feature, we can save 0.1ms
in a ping between two VFs on average.

changes from V2:
(1)rename struct vhost_call_ctx to vhost_vring_call
(2)add kvm_arch_end_assignment() in del_producer()
code path
(3)rename vDPA helpers to vdpa_devm_request_irq()
and vdpa_devm_free_irq(). Add better comments
for them.
(4)better comments for setup_vq_irq() and
unsetup_vq_irq()
(5)In vDPA VHOST_SET_VRING_CALL, will call vhost_vdpa_update_vq_irq()
without checking producer.irq, move this check into
vhost_vdpa_update_vq_irq(), so that get advantage of the spinlock.
(6)Add a function vhost_vdpa_clean_irq(), this function will unregister
the producer of vqs when vhost_vdpa_release(). This is safe
for control vq.
(7) minor improvements

changes from V1:
(1)dropped vfio changes.
(3)removed KVM_HVAE_IRQ_BYPASS checks
(4)locking fixes
(5)simplified vhost_vdpa_updat

Zhu Lingshan (6):
  vhost: introduce vhost_vring_call
  kvm: detect assigned device via irqbypass manager
  vDPA: implement vq IRQ allocate/free helpers in vDPA core
  vhost_vdpa: implement IRQ offloading in vhost_vdpa
  ifcvf: replace irq_request/free with vDPA helpers
  irqbypass: do not start cons/prod when failed connect

 arch/x86/kvm/x86.c              | 11 +++++-
 drivers/vdpa/ifcvf/ifcvf_main.c | 14 ++++---
 drivers/vdpa/vdpa.c             | 49 +++++++++++++++++++++++
 drivers/vhost/Kconfig           |  1 +
 drivers/vhost/vdpa.c            | 70 +++++++++++++++++++++++++++++++--
 drivers/vhost/vhost.c           | 22 ++++++++---
 drivers/vhost/vhost.h           |  9 ++++-
 include/linux/vdpa.h            | 13 ++++++
 virt/lib/irqbypass.c            | 16 +++++---
 9 files changed, 182 insertions(+), 23 deletions(-)