* [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts
@ 2016-03-02 11:14 George Dunlap
2016-03-02 11:14 ` [PATCH RFC 1/4] libxl: Move check for local access to a funciton George Dunlap
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: George Dunlap @ 2016-03-02 11:14 UTC (permalink / raw)
To: xen-devel; +Cc: George Dunlap
Qemu in dom0 can only provide emulated disks when the qemu process has
access to an image of the file. At the moment, this only includes
plain files or physical devices in dom0; it does not include anything
to do with a hotplug script.
However, hotplug scripts run from dom0 generally do, as a necessary
side effect of their activity, create a block device which could be
passed to domain 0; this block device can be passed to a qemu device
running in dom0 to provide emulated disk support.
This series allows qemu to gain access to that block device, giving it
full parity with PV guests for all disks whose backend is in domain 0.
It also takes steps towards generalizing the "local attach"
funcitonality which is used by pygrub to access non-local disks, so
that in the future qemu can access emulated disks by attaching them to
dom0.
RFC because I haven't tested it since forward-porting it.
George Dunlap (4):
libxl: Move check for local access to a funciton
libxl: Share logic for finding path between qemuu and pygrub
tools/hotplug: Add a "dummy" hotplug script for testing
libxl: Allow local access for block devices with hotplug scripts
tools/hotplug/Linux/Makefile | 1 +
tools/hotplug/Linux/block-common.sh | 5 +-
tools/hotplug/Linux/block-dummy | 107 +++++++++++++++++++++++++++++++++
tools/libxl/libxl.c | 115 +++++++++++++++++++++++++++++-------
tools/libxl/libxl_bootloader.c | 1 +
tools/libxl/libxl_dm.c | 66 ++++++++++++++-------
tools/libxl/libxl_internal.h | 12 +++-
7 files changed, 262 insertions(+), 45 deletions(-)
create mode 100644 tools/hotplug/Linux/block-dummy
--
2.1.4
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http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH RFC 1/4] libxl: Move check for local access to a funciton
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
@ 2016-03-02 11:14 ` George Dunlap
2016-03-02 11:14 ` [PATCH RFC 2/4] libxl: Share logic for finding path between qemuu and pygrub George Dunlap
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: George Dunlap @ 2016-03-02 11:14 UTC (permalink / raw)
To: xen-devel
Cc: George Dunlap, Ian Jackson, Wei Liu, Ian Campbell, Roger Pau Monne
From: George Dunlap <george.dunlap@eu.citrix.com>
Move pygrub checks for local access ability into a separate function.
Also reorganize libxl__device_disk_local_initiate_attach so that we
don't initialize dls->disk unless we actually end up doing a local
attach.
Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
---
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monne <roger.pau@citrix.com>
---
tools/libxl/libxl.c | 66 +++++++++++++++++++++++++++++++++++++----------------
1 file changed, 46 insertions(+), 20 deletions(-)
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 4cdc169..bb66624 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -3016,13 +3016,38 @@ static char * libxl__alloc_vdev(libxl__gc *gc, void *get_vdev_user,
/* Callbacks */
+static char * libxl__device_disk_find_local_path(libxl__gc *gc,
+ const libxl_device_disk *disk) {
+ char *path = NULL;
+
+ /* No local paths for driver domains */
+ if (disk->backend_domname != NULL) {
+ LOG(DEBUG, "Non-local backend, can't access locally.\n");
+ goto out;
+ }
+
+ /*
+ * If this is in raw format, and we're not using a script or a
+ * driver domain, we can access the target path directly.
+ */
+ if (disk->format == LIBXL_DISK_FORMAT_RAW
+ && disk->script == NULL
+ && disk->pdev_path) {
+ path = libxl__strdup(gc, disk->pdev_path);
+ LOG(DEBUG, "Directly accessing local RAW disk %s", path);
+ goto out;
+ }
+
+ out:
+ return path;
+}
+
static void local_device_attach_cb(libxl__egc *egc, libxl__ao_device *aodev);
void libxl__device_disk_local_initiate_attach(libxl__egc *egc,
libxl__disk_local_state *dls)
{
STATE_AO_GC(dls->ao);
- char *dev = NULL;
int rc;
const libxl_device_disk *in_disk = dls->in_disk;
libxl_device_disk *disk = &dls->disk;
@@ -3030,34 +3055,35 @@ void libxl__device_disk_local_initiate_attach(libxl__egc *egc,
assert(in_disk->pdev_path);
- memcpy(disk, in_disk, sizeof(libxl_device_disk));
- disk->pdev_path = libxl__strdup(gc, in_disk->pdev_path);
- if (in_disk->script != NULL)
- disk->script = libxl__strdup(gc, in_disk->script);
disk->vdev = NULL;
- rc = libxl__device_disk_setdefault(gc, disk);
- if (rc) goto out;
+ if(dls->diskpath)
+ LOG(DEBUG, "Strange, dls->diskpath already set: %s", dls->diskpath);
- /* If this is in a driver domain, or it's not a raw format, or it involves
- * running a script, we have to do a local attach. */
- if (disk->backend_domname != NULL
- || disk->format != LIBXL_DISK_FORMAT_RAW
- || disk->script != NULL) {
+ LOG(DEBUG, "Trying to find local path");
+
+ if ((dls->diskpath = libxl__device_disk_find_local_path(gc, in_disk))) {
+ LOG(DEBUG, "Local path found, executing callback.");
+ dls->callback(egc, dls, 0);
+ } else {
+ LOG(DEBUG, "Local path not found, initiating attach.");
+
+ memcpy(disk, in_disk, sizeof(libxl_device_disk));
+ disk->pdev_path = libxl__strdup(gc, in_disk->pdev_path);
+ if (in_disk->script != NULL)
+ disk->script = libxl__strdup(gc, in_disk->script);
+ disk->vdev = NULL;
+
+ rc = libxl__device_disk_setdefault(gc, disk);
+ if (rc) goto out;
+
+ /* If we can't find a local path, attach it */
libxl__prepare_ao_device(ao, &dls->aodev);
dls->aodev.callback = local_device_attach_cb;
device_disk_add(egc, LIBXL_TOOLSTACK_DOMID, disk, &dls->aodev,
libxl__alloc_vdev, (void *) blkdev_start);
- return;
}
- LOG(DEBUG, "locally attaching RAW disk %s", disk->pdev_path);
- dev = disk->pdev_path;
-
- if (dev != NULL)
- dls->diskpath = libxl__strdup(gc, dev);
-
- dls->callback(egc, dls, 0);
return;
out:
--
2.1.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH RFC 2/4] libxl: Share logic for finding path between qemuu and pygrub
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
2016-03-02 11:14 ` [PATCH RFC 1/4] libxl: Move check for local access to a funciton George Dunlap
@ 2016-03-02 11:14 ` George Dunlap
2016-03-02 11:14 ` [PATCH RFC 3/4] tools/hotplug: Add a "dummy" hotplug script for testing George Dunlap
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: George Dunlap @ 2016-03-02 11:14 UTC (permalink / raw)
To: xen-devel
Cc: Wei Liu, Ian Campbell, George Dunlap, Stefano Stabellini,
Anthony Perard, Ian Jackson, Roger Pau Monne
From: George Dunlap <george.dunlap@eu.citrix.com>
qemu can also access disks which will be provided with a qdisk backend
directly; add a flag to libxl__device_disk_find_local_path to indicate
whether to check for qdisk direct access.
Reorganize the qemuu disk argument code to make a clean separation
between finding a file to use (if any), and constructing the
parameters.
Only use qemu_disk_format_string() in circumstances where qemu may be
interpreting the disk (i.e., backend==QDISK). In all other cases, it
should use RAW.
Share as much as possible between the is_cdrom path and the normal path.
Call libxl__device_disk_find_local_path() for most paths. If we can't find
a local path, print an error and skip the disk, rather than using a bogus path.
This should fix two bugs:
* In the case of a block script, or a non-dom0 backend, qemuu will now
print a warning and skip the disk, rather than adding bogus
parameters that will cause qemuu to error out.
* You should now be able to use any backend for a cdrom that you can
use for a normal disk. (Before it was limited to RAW files or things
that qemu could handle directly.)
I left the libxl__blktap_devpath in the qemuu-specific code rather than sharing
it with the pyrgub code because:
1) When the pygrub path runs the guest disks have not yet been set up
2) libxl__blktap_devpath() will give you the existing devpath if it
already exists, but will set one up for you if you don't. So on the pygrub path,
this would end up setting up a new tap device.
3) There is no TAP-specific teardown code on the pygrub path, and I
don't want to add any (particularly since I'm hoping to remove tapdisk
altogether soon).
Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
---
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Stefano Stabellini <stefano.stabellini@citrix.com>
CC: Anthony Perard <anthony.perard@citrix.com>
CC: Roger Pau Monne <roger.pau@citrix.com>
---
tools/libxl/libxl.c | 17 ++++++++++--
tools/libxl/libxl_dm.c | 66 +++++++++++++++++++++++++++++---------------
tools/libxl/libxl_internal.h | 8 ++++++
3 files changed, 66 insertions(+), 25 deletions(-)
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index bb66624..2f66c3a 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -3016,8 +3016,9 @@ static char * libxl__alloc_vdev(libxl__gc *gc, void *get_vdev_user,
/* Callbacks */
-static char * libxl__device_disk_find_local_path(libxl__gc *gc,
- const libxl_device_disk *disk) {
+char * libxl__device_disk_find_local_path(libxl__gc *gc,
+ const libxl_device_disk *disk,
+ bool qdisk_direct) {
char *path = NULL;
/* No local paths for driver domains */
@@ -3038,6 +3039,16 @@ static char * libxl__device_disk_find_local_path(libxl__gc *gc,
goto out;
}
+ /*
+ * If we're being called for a qemu path, we can pass the target
+ * string directly as well
+ */
+ if (qdisk_direct && disk->backend == LIBXL_DISK_BACKEND_QDISK ) {
+ path = libxl__strdup(gc, disk->pdev_path);
+ LOG(DEBUG, "Directly accessing local QDISK target %s", path);
+ goto out;
+ }
+
out:
return path;
}
@@ -3062,7 +3073,7 @@ void libxl__device_disk_local_initiate_attach(libxl__egc *egc,
LOG(DEBUG, "Trying to find local path");
- if ((dls->diskpath = libxl__device_disk_find_local_path(gc, in_disk))) {
+ if ((dls->diskpath = libxl__device_disk_find_local_path(gc, in_disk, false))) {
LOG(DEBUG, "Local path found, executing callback.");
dls->callback(egc, dls, 0);
} else {
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 4aca38e..917ebbf 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1161,9 +1161,9 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
int disk, part;
int dev_number =
libxl__device_disk_dev_number(disks[i].vdev, &disk, &part);
- const char *format = qemu_disk_format_string(disks[i].format);
+ const char *format;
char *drive;
- const char *pdev_path;
+ const char *target_path;
if (dev_number == -1) {
LOG(WARN, "unable to determine"" disk number for %s",
@@ -1171,22 +1171,22 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
continue;
}
- if (disks[i].is_cdrom) {
- if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY)
- drive = libxl__sprintf
- (gc, "if=ide,index=%d,readonly=%s,media=cdrom,cache=writeback,id=ide-%i",
- disk, disks[i].readwrite ? "off" : "on", dev_number);
- else
- drive = libxl__sprintf
- (gc, "file=%s,if=ide,index=%d,readonly=%s,media=cdrom,format=%s,cache=writeback,id=ide-%i",
- disks[i].pdev_path, disk, disks[i].readwrite ? "off" : "on", format, dev_number);
- } else {
- if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY) {
+ /*
+ * If qemu isn't doing the interpreting, the parameter is
+ * always raw
+ */
+ if (disks[i].backend == LIBXL_DISK_BACKEND_QDISK)
+ format = qemu_disk_format_string(disks[i].format);
+ else
+ format = qemu_disk_format_string(LIBXL_DISK_FORMAT_RAW);
+
+ if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY) {
+ if (!disks[i].is_cdrom) {
LOG(WARN, "cannot support"" empty disk format for %s",
disks[i].vdev);
continue;
}
-
+ } else {
if (format == NULL) {
LOG(WARN,
"unable to determine"" disk image format %s",
@@ -1194,14 +1194,36 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
continue;
}
- if (disks[i].backend == LIBXL_DISK_BACKEND_TAP) {
- format = qemu_disk_format_string(LIBXL_DISK_FORMAT_RAW);
- pdev_path = libxl__blktap_devpath(gc, disks[i].pdev_path,
+ /*
+ * We can't call libxl__blktap_devpath from
+ * libxl__device_disk_find_local_path for now because
+ * the bootloader is called before the disks are set
+ * up, so this function would set up a blktap node,
+ * but there's no TAP tear-down on error conditions in
+ * the bootloader path.
+ */
+ if (disks[i].backend == LIBXL_DISK_BACKEND_TAP)
+ target_path = libxl__blktap_devpath(gc, disks[i].pdev_path,
disks[i].format);
- } else {
- pdev_path = disks[i].pdev_path;
+ else
+ target_path = libxl__device_disk_find_local_path(gc,
+ &disks[i], true);
+
+ if (!target_path) {
+ LOG(WARN, "No way to get local access disk to image: %s", disks[i].vdev);
+ continue;
}
+ }
+
+ if (disks[i].is_cdrom) {
+ drive = libxl__sprintf
+ (gc, "if=ide,index=%d,readonly=%s,media=cdrom,cache=writeback,id=ide-%i",
+ disk, disks[i].readwrite ? "off" : "on", dev_number);
+ if (target_path)
+ drive = libxl__sprintf(gc, "%s,file=%s,format=%s",
+ drive, target_path, format);
+ } else {
/*
* Explicit sd disks are passed through as is.
*
@@ -1211,7 +1233,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
if (strncmp(disks[i].vdev, "sd", 2) == 0) {
drive = libxl__sprintf
(gc, "file=%s,if=scsi,bus=0,unit=%d,format=%s,readonly=%s,cache=writeback",
- pdev_path, disk, format, disks[i].readwrite ? "off" : "on");
+ target_path, disk, format, disks[i].readwrite ? "off" : "on");
} else if (strncmp(disks[i].vdev, "xvd", 3) == 0) {
/*
* Do not add any emulated disk when PV disk are
@@ -1225,7 +1247,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
}
flexarray_vappend(dm_args, "-drive",
GCSPRINTF("file=%s,if=none,id=ahcidisk-%d,format=%s,cache=writeback",
- pdev_path, disk, format),
+ target_path, disk, format),
"-device", GCSPRINTF("ide-hd,bus=ahci0.%d,unit=0,drive=ahcidisk-%d",
disk, disk), NULL);
continue;
@@ -1236,7 +1258,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
}
drive = libxl__sprintf
(gc, "file=%s,if=ide,index=%d,media=disk,format=%s,cache=writeback",
- pdev_path, disk, format);
+ target_path, disk, format);
} else {
continue; /* Do not emulate this disk */
}
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index a1aae97..265b8a2 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2670,6 +2670,14 @@ static inline void libxl__device_disk_local_init(libxl__disk_local_state *dls)
dls->rc = 0;
}
+/*
+ * See if we can find a way to access a disk locally
+ */
+_hidden char * libxl__device_disk_find_local_path(libxl__gc *gc,
+ const libxl_device_disk *disk,
+ bool qdisk_direct);
+
+
/* Make a disk available in this (the control) domain. Always calls
* dls->callback when finished.
* State Idle -> Attaching
--
2.1.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH RFC 3/4] tools/hotplug: Add a "dummy" hotplug script for testing
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
2016-03-02 11:14 ` [PATCH RFC 1/4] libxl: Move check for local access to a funciton George Dunlap
2016-03-02 11:14 ` [PATCH RFC 2/4] libxl: Share logic for finding path between qemuu and pygrub George Dunlap
@ 2016-03-02 11:14 ` George Dunlap
2016-03-02 11:14 ` [PATCH RFC 4/4] libxl: Allow local access for block devices with hotplug scripts George Dunlap
2016-03-08 19:18 ` [PATCH RFC 0/4] Allow qemu to provide emulated disks for " Wei Liu
4 siblings, 0 replies; 6+ messages in thread
From: George Dunlap @ 2016-03-02 11:14 UTC (permalink / raw)
To: xen-devel
Cc: George Dunlap, Ian Jackson, Wei Liu, Ian Campbell, Roger Pau Monne
From: George Dunlap <george.dunlap@eu.citrix.com>
Testing the hotplug external script path at the moment involves
actually setting up one of the alternate datapaths (blktap, iscsi,
&c). Simplify testing by making a script which does a simple loopback,
but still has a target that can't be used directly.
To use:
script=block-dummy,vdev=xvda,target=dummy:<file>
Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
---
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monne <roger.pau@citrix.com>
---
tools/hotplug/Linux/Makefile | 1 +
tools/hotplug/Linux/block-dummy | 107 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 108 insertions(+)
diff --git a/tools/hotplug/Linux/Makefile b/tools/hotplug/Linux/Makefile
index 6e10118..dcfd58a 100644
--- a/tools/hotplug/Linux/Makefile
+++ b/tools/hotplug/Linux/Makefile
@@ -27,6 +27,7 @@ XEN_SCRIPTS += vscsi
XEN_SCRIPTS += block-iscsi
XEN_SCRIPTS += block-tap
XEN_SCRIPTS += block-drbd-probe
+XEN_SCRIPTS += block-dummy
XEN_SCRIPTS += $(XEN_SCRIPTS-y)
SUBDIRS-$(CONFIG_SYSTEMD) += systemd
diff --git a/tools/hotplug/Linux/block-dummy b/tools/hotplug/Linux/block-dummy
new file mode 100644
index 0000000..57d40b5
--- /dev/null
+++ b/tools/hotplug/Linux/block-dummy
@@ -0,0 +1,107 @@
+#!/bin/bash -e
+#
+# dummy Xen block device hotplug script
+#
+# Author George Dunlap <george.dunlap@eu.citrix.com>
+#
+# Based on block-iscsi by Roger Pau Monné <roger.pau@citrix.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published
+# by the Free Software Foundation; version 2.1 only. with the special
+# exception on linking described in file LICENSE.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Lesser General Public License for more details.
+#
+# Usage:
+#
+# Target should be specified using the following syntax:
+#
+# script=block-dummy,vdev=xvda,target=dummy:<file>
+
+dir=$(dirname "$0")
+. "$dir/block-common.sh"
+
+check_tools()
+{
+ if ! command -v losetup > /dev/null 2>&1; then
+ fatal "Unable to find losetup"
+ fi
+}
+
+# Sets the following global variables based on the params field passed in as
+# a parameter: type file
+parse_target()
+{
+ params=($(echo "$1" | tr ":" "\n"))
+
+ type=${params[0]}
+ file=${params[1]}
+ if [ -z "$type" ] || [ -z "$file" ]; then
+ fatal "Cannot parse required parameters"
+ fi
+
+ if [ "$type" != "dummy" ] ; then
+ fatal "Invalid type: $type"
+ fi
+}
+
+# Attaches the device and writes xenstore backend entries to connect
+# the device
+add()
+{
+ test -f "$file" || fatal "$file does not exist."
+
+ loopdev=$(losetup -f 2>/dev/null || find_free_loopback_dev)
+ if [ "$loopdev" = '' ]
+ then
+ fatal 'Failed to find an unused loop device'
+ fi
+
+ if LANG=C losetup -h 2>&1 | grep read-only >/dev/null
+ then
+ roflag="-$mode"; roflag="${roflag#-w}"; roflag="${roflag#-!}"
+ else
+ roflag=''
+ fi
+
+ do_or_die losetup $roflag "$loopdev" "$file"
+ # FIXME Is this OK?
+ xenstore_write "$XENBUS_PATH/node" "$loopdev"
+ write_dev "$loopdev"
+}
+
+# Disconnects the device
+remove()
+{
+ node=$(xenstore_read "$XENBUS_PATH/node")
+ losetup -d "$node"
+}
+
+command=$1
+target=$(xenstore-read $XENBUS_PATH/params || true)
+if [ -z "$target" ]; then
+ fatal "No information about the target"
+fi
+
+parse_target "$target"
+
+mode=$(xenstore_read "$XENBUS_PATH/mode")
+mode=$(canonicalise_mode "$mode")
+
+check_tools || exit 1
+
+case $command in
+add)
+ add
+ ;;
+remove)
+ remove
+ ;;
+*)
+ exit 1
+ ;;
+esac
--
2.1.4
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http://lists.xen.org/xen-devel
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH RFC 4/4] libxl: Allow local access for block devices with hotplug scripts
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
` (2 preceding siblings ...)
2016-03-02 11:14 ` [PATCH RFC 3/4] tools/hotplug: Add a "dummy" hotplug script for testing George Dunlap
@ 2016-03-02 11:14 ` George Dunlap
2016-03-08 19:18 ` [PATCH RFC 0/4] Allow qemu to provide emulated disks for " Wei Liu
4 siblings, 0 replies; 6+ messages in thread
From: George Dunlap @ 2016-03-02 11:14 UTC (permalink / raw)
To: xen-devel
Cc: George Dunlap, Ian Jackson, Wei Liu, Ian Campbell, Roger Pau Monne
From: George Dunlap <george.dunlap@eu.citrix.com>
pygrub and qemuu need to be able to access a VM's disks locally in
order to be able to pull out the kernel and provide emulated disk
access, respectively. This can be done either by accessing the local
disk directly, or by plugging the target disk into dom0 to allow
access.
Unfortunately, while the plugging machinery works for pygrub, it does
not yet work for qemuu; meaning that disk hotplug scripts cannot be
used with HVM domains.
Fortunately, disks using hotplug scripts created in dom0 do create a
block device as part of set-up, which can be accessed locally.
First, modify the write_dev function in block-common to add an extra
parameter: "physical-device-path", the path to the physical device
which is passed to blkback. All hotplug scripts that use write_dev
will automatically gain the new functionality.
Second, modify libxl__device_disk_setdefault() to be able to fish this
path out of xenstore and pass it back.
We need the target domid to find the appropriate xenstore node, so add that to
libxl__disk_local_state.
This allows qemuu to boot with block devices created with hotplug scripts.
Unfortunately it does not allow pygrub to access a device locally
without having to plug it in, because when pygrub runs the guests'
disks have not yet been set up.
Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
---
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monne <roger.pau@citrix.com>
---
tools/hotplug/Linux/block-common.sh | 5 ++++-
tools/libxl/libxl.c | 42 ++++++++++++++++++++++++++++++++++---
tools/libxl/libxl_bootloader.c | 1 +
tools/libxl/libxl_dm.c | 2 +-
tools/libxl/libxl_internal.h | 4 +++-
5 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/tools/hotplug/Linux/block-common.sh b/tools/hotplug/Linux/block-common.sh
index ee95009..1aecd7e 100644
--- a/tools/hotplug/Linux/block-common.sh
+++ b/tools/hotplug/Linux/block-common.sh
@@ -58,8 +58,9 @@ device_major_minor()
#
write_dev() {
local mm
+ local dev="$1"
- mm=$(device_major_minor "$1")
+ mm=$(device_major_minor "$dev")
if [ -z $mm ]
then
@@ -68,6 +69,8 @@ write_dev() {
xenstore_write "$XENBUS_PATH/physical-device" "$mm"
+ xenstore_write "$XENBUS_PATH/physical-device-path" "$dev"
+
success
}
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 2f66c3a..cc97fa8 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2296,7 +2296,7 @@ int libxl__device_disk_setdefault(libxl__gc *gc, libxl_device_disk *disk)
}
int libxl__device_from_disk(libxl__gc *gc, uint32_t domid,
- libxl_device_disk *disk,
+ const libxl_device_disk *disk,
libxl__device *device)
{
int devid;
@@ -2454,6 +2454,7 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
if (!libxl__device_physdisk_major_minor(dev, &major, &minor))
flexarray_append_pair(back, "physical-device",
GCSPRINTF("%x:%x", major, minor));
+ flexarray_append_pair(back, "physical-device-path", dev);
}
assert(device->backend_kind == LIBXL__DEVICE_KIND_VBD);
@@ -3017,6 +3018,7 @@ static char * libxl__alloc_vdev(libxl__gc *gc, void *get_vdev_user,
/* Callbacks */
char * libxl__device_disk_find_local_path(libxl__gc *gc,
+ libxl_domid domid,
const libxl_device_disk *disk,
bool qdisk_direct) {
char *path = NULL;
@@ -3047,6 +3049,40 @@ char * libxl__device_disk_find_local_path(libxl__gc *gc,
path = libxl__strdup(gc, disk->pdev_path);
LOG(DEBUG, "Directly accessing local QDISK target %s", path);
goto out;
+ }
+
+ /*
+ * If the format isn't raw and / or we're using a script, then see
+ * if the script has written a path to the "cooked" node
+ */
+ if(disk->script) {
+ libxl__device device;
+ char * be_path, *pdpath;
+ int rc;
+
+ LOG(DEBUG, "Run from a script; checking for physical-device-path (vdev %s)",
+ disk->vdev);
+
+ rc = libxl__device_from_disk(gc, domid, disk, &device);
+ if (rc < 0)
+ goto out;
+
+ /* Needs: dompath, device type, domid */
+ be_path = libxl__device_backend_path(gc, &device);
+
+ /* FIXME: Do we need to wait for things to be set up here? */
+
+ pdpath = libxl__sprintf(gc, "%s/physical-device-path", be_path);
+
+ LOG(DEBUG, "Attempting to read node %s", pdpath);
+ path = libxl__xs_read(gc, XBT_NULL, pdpath);
+
+ if (path)
+ LOG(DEBUG, "Accessing cooked block device %s", path);
+ else
+ LOG(DEBUG, "No physical-device-path, can't access locally.");
+
+ goto out;
}
out:
@@ -3073,7 +3109,8 @@ void libxl__device_disk_local_initiate_attach(libxl__egc *egc,
LOG(DEBUG, "Trying to find local path");
- if ((dls->diskpath = libxl__device_disk_find_local_path(gc, in_disk, false))) {
+ if ((dls->diskpath = libxl__device_disk_find_local_path(gc, dls->domid,
+ in_disk, false))) {
LOG(DEBUG, "Local path found, executing callback.");
dls->callback(egc, dls, 0);
} else {
@@ -3088,7 +3125,6 @@ void libxl__device_disk_local_initiate_attach(libxl__egc *egc,
rc = libxl__device_disk_setdefault(gc, disk);
if (rc) goto out;
- /* If we can't find a local path, attach it */
libxl__prepare_ao_device(ao, &dls->aodev);
dls->aodev.callback = local_device_attach_cb;
device_disk_add(egc, LIBXL_TOOLSTACK_DOMID, disk, &dls->aodev,
diff --git a/tools/libxl/libxl_bootloader.c b/tools/libxl/libxl_bootloader.c
index 0ae074a..5648ed7 100644
--- a/tools/libxl/libxl_bootloader.c
+++ b/tools/libxl/libxl_bootloader.c
@@ -382,6 +382,7 @@ void libxl__bootloader_run(libxl__egc *egc, libxl__bootloader_state *bl)
/* This sets the state of the dls struct from Undefined to Idle */
libxl__device_disk_local_init(&bl->dls);
bl->dls.ao = ao;
+ bl->dls.domid = bl->domid;
bl->dls.in_disk = bl->disk;
bl->dls.blkdev_start = info->blkdev_start;
bl->dls.callback = bootloader_disk_attached_cb;
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 917ebbf..5bd4dad 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1207,7 +1207,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
disks[i].format);
else
target_path = libxl__device_disk_find_local_path(gc,
- &disks[i], true);
+ guest_domid, &disks[i], true);
if (!target_path) {
LOG(WARN, "No way to get local access disk to image: %s", disks[i].vdev);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 265b8a2..b773e5a 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1709,7 +1709,7 @@ _hidden char *libxl__blktap_devpath(libxl__gc *gc,
_hidden int libxl__device_destroy_tapdisk(libxl__gc *gc, const char *params);
_hidden int libxl__device_from_disk(libxl__gc *gc, uint32_t domid,
- libxl_device_disk *disk,
+ const libxl_device_disk *disk,
libxl__device *device);
/* Calls poll() again - useful to check whether a signaled condition
@@ -2650,6 +2650,7 @@ typedef void libxl__disk_local_state_callback(libxl__egc*,
struct libxl__disk_local_state {
/* filled by the user */
libxl__ao *ao;
+ libxl_domid domid;
const libxl_device_disk *in_disk;
libxl_device_disk disk;
const char *blkdev_start;
@@ -2674,6 +2675,7 @@ static inline void libxl__device_disk_local_init(libxl__disk_local_state *dls)
* See if we can find a way to access a disk locally
*/
_hidden char * libxl__device_disk_find_local_path(libxl__gc *gc,
+ libxl_domid domid,
const libxl_device_disk *disk,
bool qdisk_direct);
--
2.1.4
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Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
` (3 preceding siblings ...)
2016-03-02 11:14 ` [PATCH RFC 4/4] libxl: Allow local access for block devices with hotplug scripts George Dunlap
@ 2016-03-08 19:18 ` Wei Liu
4 siblings, 0 replies; 6+ messages in thread
From: Wei Liu @ 2016-03-08 19:18 UTC (permalink / raw)
To: George Dunlap; +Cc: Wei Liu, xen-devel
On Wed, Mar 02, 2016 at 11:14:00AM +0000, George Dunlap wrote:
> Qemu in dom0 can only provide emulated disks when the qemu process has
> access to an image of the file. At the moment, this only includes
> plain files or physical devices in dom0; it does not include anything
> to do with a hotplug script.
>
> However, hotplug scripts run from dom0 generally do, as a necessary
> side effect of their activity, create a block device which could be
> passed to domain 0; this block device can be passed to a qemu device
> running in dom0 to provide emulated disk support.
>
> This series allows qemu to gain access to that block device, giving it
> full parity with PV guests for all disks whose backend is in domain 0.
>
> It also takes steps towards generalizing the "local attach"
> funcitonality which is used by pygrub to access non-local disks, so
> that in the future qemu can access emulated disks by attaching them to
> dom0.
>
> RFC because I haven't tested it since forward-porting it.
>
I haven't looked at this series, but I expect another posting on top of
Ian Jackson's hotplug script interface patch.
If you want me to look at this series, please let me know.
Wei.
>
> George Dunlap (4):
> libxl: Move check for local access to a funciton
> libxl: Share logic for finding path between qemuu and pygrub
> tools/hotplug: Add a "dummy" hotplug script for testing
> libxl: Allow local access for block devices with hotplug scripts
>
> tools/hotplug/Linux/Makefile | 1 +
> tools/hotplug/Linux/block-common.sh | 5 +-
> tools/hotplug/Linux/block-dummy | 107 +++++++++++++++++++++++++++++++++
> tools/libxl/libxl.c | 115 +++++++++++++++++++++++++++++-------
> tools/libxl/libxl_bootloader.c | 1 +
> tools/libxl/libxl_dm.c | 66 ++++++++++++++-------
> tools/libxl/libxl_internal.h | 12 +++-
> 7 files changed, 262 insertions(+), 45 deletions(-)
> create mode 100644 tools/hotplug/Linux/block-dummy
>
> --
> 2.1.4
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-03-08 19:18 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-03-02 11:14 [PATCH RFC 0/4] Allow qemu to provide emulated disks for devices with hotplug scripts George Dunlap
2016-03-02 11:14 ` [PATCH RFC 1/4] libxl: Move check for local access to a funciton George Dunlap
2016-03-02 11:14 ` [PATCH RFC 2/4] libxl: Share logic for finding path between qemuu and pygrub George Dunlap
2016-03-02 11:14 ` [PATCH RFC 3/4] tools/hotplug: Add a "dummy" hotplug script for testing George Dunlap
2016-03-02 11:14 ` [PATCH RFC 4/4] libxl: Allow local access for block devices with hotplug scripts George Dunlap
2016-03-08 19:18 ` [PATCH RFC 0/4] Allow qemu to provide emulated disks for " Wei Liu
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