[src/trunk]: src/sys/rump/net/lib/libshmif Prefault bus pages in driver attac...

[pooka <pooka%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d8d57a32099c
branches:  trunk
changeset: 757177:d8d57a32099c
user:      pooka <pooka%NetBSD.org@localhost>
date:      Tue Aug 17 20:42:47 2010 +0000

description:
Prefault bus pages in driver attachment.  This seems to work around
weird corruption I've been seeing (most likely a host kernel bug).

For more details, see thread at:
http://mail-index.netbsd.org/tech-kern/2010/08/17/msg008749.html

diffstat:

 sys/rump/net/lib/libshmif/if_shmem.c |  32 ++++++++++++++++++++++++++++++--
 1 files changed, 30 insertions(+), 2 deletions(-)

diffs (74 lines):

diff -r f064b55baad8 -r d8d57a32099c sys/rump/net/lib/libshmif/if_shmem.c
--- a/sys/rump/net/lib/libshmif/if_shmem.c      Tue Aug 17 18:53:16 2010 +0000
+++ b/sys/rump/net/lib/libshmif/if_shmem.c      Tue Aug 17 20:42:47 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_shmem.c,v 1.27 2010/08/17 11:35:23 pooka Exp $      */
+/*     $NetBSD: if_shmem.c,v 1.28 2010/08/17 20:42:47 pooka Exp $      */
 
 /*
  * Copyright (c) 2009 Antti Kantee.  All Rights Reserved.
@@ -28,7 +28,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_shmem.c,v 1.27 2010/08/17 11:35:23 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_shmem.c,v 1.28 2010/08/17 20:42:47 pooka Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -51,6 +51,16 @@
 #include "rump_net_private.h"
 
 /*
+ * Do r/w prefault for backend pages when attaching the interface.
+ * This works aroud the most likely kernel/ffs/x86pmap bug described
+ * in http://mail-index.netbsd.org/tech-kern/2010/08/17/msg008749.html
+ *
+ * NOTE: read prefaulting is not enough (that's done always)!
+ */
+
+#define PREFAULT_RW
+
+/*
  * A virtual ethernet interface which uses shared memory from a
  * memory mapped file as the bus.
  */
@@ -127,6 +137,8 @@
        uint8_t enaddr[ETHER_ADDR_LEN] = { 0xb2, 0xa0, 0x00, 0x00, 0x00, 0x00 };
        uint32_t randnum;
        unsigned mynum;
+       volatile uint8_t v;
+       volatile uint8_t *p;
        int error;
 
        randnum = arc4random();
@@ -149,6 +161,13 @@
        if (sc->sc_busmem->shm_magic && sc->sc_busmem->shm_magic != SHMIF_MAGIC)
                panic("bus is not magical");
 
+
+       /* Prefault in pages to minimize runtime penalty with buslock */
+       for (p = (uint8_t *)sc->sc_busmem;
+           p < (uint8_t *)sc->sc_busmem + BUSMEM_SIZE;
+           p += PAGE_SIZE)
+               v = *p;
+
        shmif_lockbus(sc->sc_busmem);
        /* we're first?  initialize bus */
        if (sc->sc_busmem->shm_magic == 0) {
@@ -158,6 +177,15 @@
 
        sc->sc_nextpacket = sc->sc_busmem->shm_last;
        sc->sc_devgen = sc->sc_busmem->shm_gen;
+
+#ifdef PREFAULT_RW
+       for (p = (uint8_t *)sc->sc_busmem;
+           p < (uint8_t *)sc->sc_busmem + BUSMEM_SIZE;
+           p += PAGE_SIZE) {
+               v = *p;
+               *p = v;
+       }
+#endif
        shmif_unlockbus(sc->sc_busmem);
 
        sc->sc_kq = rumpuser_writewatchfile_setup(-1, sc->sc_memfd, 0, &error);