CVS commit: src/sys/arch/xen/xen

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Wed Aug  9 08:38:47 UTC 2023

Modified Files:
        src/sys/arch/xen/xen: xennetback_xenbus.c

Log Message:
xvif(4): Omit needless membars in xennetback_rx_copy_process.

- No need for barrier around touching req_cons and rsp_prod_pvt,
  which are private.

- RING_PUSH_RESPONSES_AND_CHECK_NOTIFY updates the shared req_prod and
  then issues xen_mb, which is all that we need between the update of
  shared req_prod and hypervisor_notify_via_evtchn.

  (Between updating the shared req_prod and issuing
  hypervisor_notify_via_evtchn, only xen_wmb is needed.  But after
  writing to the shared req_prod, RING_PUSH_REQUESTS_AND_CHECK_NOTIFY
  must also read from the shared rsp_event, which requires the
  store-before-load ordering that only xen_mb provides.)


To generate a diff of this commit:
cvs rdiff -u -r1.121 -r1.122 src/sys/arch/xen/xen/xennetback_xenbus.c

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