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.
Modified files:
Index: src/sys/arch/xen/xen/xennetback_xenbus.c
diff -u src/sys/arch/xen/xen/xennetback_xenbus.c:1.121 src/sys/arch/xen/xen/xennetback_xenbus.c:1.122
--- src/sys/arch/xen/xen/xennetback_xenbus.c:1.121 Wed Aug 9 08:38:37 2023
+++ src/sys/arch/xen/xen/xennetback_xenbus.c Wed Aug 9 08:38:47 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: xennetback_xenbus.c,v 1.121 2023/08/09 08:38:37 riastradh Exp $ */
+/* $NetBSD: xennetback_xenbus.c,v 1.122 2023/08/09 08:38:47 riastradh Exp $ */
/*
* Copyright (c) 2006 Manuel Bouyer.
@@ -25,7 +25,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xennetback_xenbus.c,v 1.121 2023/08/09 08:38:37 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xennetback_xenbus.c,v 1.122 2023/08/09 08:38:47 riastradh Exp $");
#include <sys/types.h>
#include <sys/param.h>
@@ -1024,14 +1024,12 @@ xennetback_rx_copy_process(struct ifnet
}
/* update pointer */
- xen_rmb();
xneti->xni_rxring.req_cons += queued;
xneti->xni_rxring.rsp_prod_pvt += queued;
RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&xneti->xni_rxring, notify);
/* send event */
if (notify) {
- xen_rmb();
XENPRINTF(("%s receive event\n",
xneti->xni_if.if_xname));
hypervisor_notify_via_evtchn(xneti->xni_evtchn);
