[src/trunk]: src/sys/arch/xen/xen implement DIOCGCACHE - assume if CACHE_FLUS...

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

details:   https://anonhg.NetBSD.org/src/rev/d857ce88f748
branches:  trunk
changeset: 1009021:d857ce88f748
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Fri Apr 10 10:30:10 2020 +0000

description:
implement DIOCGCACHE - assume if CACHE_FLUSH is supported, write cache
is enabled

convert the sc_cache_flush flag to a feature bit field, and recognize
also barrier and persistent features; print the recognized features
on boot, and remove the warning on DIOCCACHESYNC

diffstat:

 sys/arch/xen/xen/xbd_xenbus.c |  64 ++++++++++++++++++++++++++++++------------
 1 files changed, 45 insertions(+), 19 deletions(-)

diffs (123 lines):

diff -r 934237c250e2 -r d857ce88f748 sys/arch/xen/xen/xbd_xenbus.c
--- a/sys/arch/xen/xen/xbd_xenbus.c     Fri Apr 10 08:35:52 2020 +0000
+++ b/sys/arch/xen/xen/xbd_xenbus.c     Fri Apr 10 10:30:10 2020 +0000
@@ -1,4 +1,4 @@
-/*      $NetBSD: xbd_xenbus.c,v 1.97 2020/04/07 11:47:06 jdolecek Exp $      */
+/*      $NetBSD: xbd_xenbus.c,v 1.98 2020/04/10 10:30:10 jdolecek Exp $      */
 
 /*
  * Copyright (c) 2006 Manuel Bouyer.
@@ -50,7 +50,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.97 2020/04/07 11:47:06 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.98 2020/04/10 10:30:10 jdolecek Exp $");
 
 #include "opt_xen.h"
 
@@ -150,7 +150,12 @@
        uint64_t sc_xbdsize; /* size of disk in DEV_BSIZE */
        u_long sc_info; /* VDISK_* */
        u_long sc_handle; /* from backend */
-       int sc_cache_flush; /* backend supports BLKIF_OP_FLUSH_DISKCACHE */
+       int sc_features;
+#define BLKIF_FEATURE_CACHE_FLUSH      0x1
+#define BLKIF_FEATURE_BARRIER          0x2
+#define BLKIF_FEATURE_PERSISTENT       0x4
+#define BLKIF_FEATURE_BITS             \
+       "\20\1CACHE-FLUSH\2BARRIER\3PERSISTENT"
        struct evcnt sc_cnt_map_unalign;
 };
 
@@ -509,7 +514,7 @@
        struct xbd_xenbus_softc *sc = device_private((device_t)arg);
        struct disk_geom *dg;
 
-       char buf[9];
+       char buf[32];
        int s;
        DPRINTF(("%s: new backend state %d\n",
            device_xname(sc->sc_dksc.sc_dev), new_state));
@@ -569,6 +574,9 @@
                aprint_normal_dev(sc->sc_dksc.sc_dev,
                                "%s, %d bytes/sect x %" PRIu64 " sectors\n",
                                buf, (int)dg->dg_secsize, sc->sc_xbdsize);
+               snprintb(buf, sizeof(buf), BLKIF_FEATURE_BITS,
+                   sc->sc_features);
+               aprint_normal_dev(sc->sc_dksc.sc_dev, "features %s\n", buf);
 
                /* Discover wedges on this disk. */
                dkwedge_discover(&sc->sc_dksc.sc_dkdev);
@@ -588,7 +596,7 @@
 {
        int err;
        unsigned long long sectors;
-       u_long cache_flush;
+       u_long val;
 
        err = xenbus_read_ul(NULL,
            sc->sc_xbusd->xbusd_path, "virtual-device", &sc->sc_handle, 10);
@@ -618,13 +626,25 @@
                    sc->sc_xbusd->xbusd_otherend);
 
        err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
-           "feature-flush-cache", &cache_flush, 10);
+           "feature-flush-cache", &val, 10);
+       if (err)
+               val = 0;
+       if (val > 0)
+               sc->sc_features |= BLKIF_FEATURE_CACHE_FLUSH;
+
+       err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
+           "feature-barrier", &val, 10);
        if (err)
-               cache_flush = 0;
-       if (cache_flush > 0)
-               sc->sc_cache_flush = 1;
-       else
-               sc->sc_cache_flush = 0;
+               val = 0;
+       if (val > 0)
+               sc->sc_features |= BLKIF_FEATURE_BARRIER;
+
+       err = xenbus_read_ul(NULL, sc->sc_xbusd->xbusd_otherend,
+           "feature-persistent", &val, 10);
+       if (err)
+               val = 0;
+       if (val > 0)
+               sc->sc_features |= BLKIF_FEATURE_PERSISTENT;
 
        xenbus_switch_state(sc->sc_xbusd, NULL, XenbusStateConnected);
 }
@@ -834,16 +854,22 @@
        case DIOCSSTRATEGY:
                error = EOPNOTSUPP;
                break;
+       case DIOCGCACHE:
+           {
+               /*
+                * Assume there is read & write cache if cache-flush is
+                * supported.
+                */
+               int *bitsp = (int *)data;
+               *bitsp = 0;
+               if (sc->sc_features & BLKIF_FEATURE_CACHE_FLUSH)
+                       *bitsp |= DKCACHE_WRITE;
+               error = 0;
+               break;
+           }
        case DIOCCACHESYNC:
-               if (sc->sc_cache_flush <= 0) {
-                       if (sc->sc_cache_flush == 0) {
-                               aprint_verbose_dev(sc->sc_dksc.sc_dev,
-                                   "WARNING: cache flush not supported "
-                                   "by backend\n");
-                               sc->sc_cache_flush = -1;
-                       }
+               if ((sc->sc_features & BLKIF_FEATURE_CACHE_FLUSH) == 0)
                        return EOPNOTSUPP;
-               }
 
                s = splbio(); /* XXXSMP */