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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4] libxl: fix migration of PV and PVH domUs with and without qemu
On Fri, May 10, 2019 at 05:20:47PM +0200, Olaf Hering wrote:
> If a domU has a qemu-xen instance attached, it is required to call qemus
> "xen-save-devices-state" method. Without it, the receiving side of a PV or
> PVH migration may be unable to lock the image:
>
> xen be: qdisk-51712: xen be: qdisk-51712: error: Failed to get "write" lock
> error: Failed to get "write" lock
> xen be: qdisk-51712: xen be: qdisk-51712: initialise() failed
> initialise() failed
>
> To fix this bug, libxl__domain_suspend_device_model() and
> libxl__domain_resume_device_model() have to be called not only for HVM,
> but also if the active device_model is QEMU_XEN.
>
> Unfortunately, libxl__domain_build_info_setdefault() hardcodes
> b_info->device_model_version to QEMU_XEN if it does not know it any
> better. As a result libxl__device_model_version_running() will return
> incorrect values. This breaks domUs without a device_model.
> libxl__qmp_stop() would wait 10 seconds in qmp_open() for a qemu that
> will never appear. During this long timeframe the domU remains in state
> paused on the sending side. As a result network connections may be
> dropped. Once this bug is fixed as well, by just removing the assumption
> that every domU has a QEMU_XEN, there is no code to actually initialise
> b_info->device_model_version.
>
> There is a helper function libxl__need_xenpv_qemu(), which is used in
> various places to decide if a device_model has to be spawned. This
> function can not be used as is, just to fill device_model_version,
> because store_libxl_entry() was already called earlier.
>
> Create a new function to set device_model_version. Move existing code
> from libxl__domain_build_info_setdefault() to cover the HVM case. Add
> new code to cover non-HVM case, use libxl__need_xenpv_qemu() to set
> device_model_version.
> Move also initialization for device_model_stubdomain to the new function.
>
> Update libxl__spawn_stub_dm() and initiate_domain_create() to call the
> new function prior libxl__domain_build_info_setdefault() because
> device_mode_version is expected to be initialzed.
> libxl_domain_need_memory() needs no update because it does not have a
> d_config available anyway, and the callers provide a populated b_info.
>
> Introduce LIBXL_DEVICE_MODEL_VERSION_NONE_REQUIRED for PV and PVH that
> have no need for a device_model to make the state explicit.
>
> v03:
> - rearrange code to make sure device_model_version is initialized before
> store_libxl_entry() is called
> v02:
> - update wording in a comment
> - remove stale goto in domcreate_launch_dm
> - initialize ret in libxl__need_xenpv_qemu
>
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
LGTM:
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> tools/libxl/libxl_create.c | 99
> ++++++++++++++++++++++++++---------------
> tools/libxl/libxl_dm.c | 2 +
> tools/libxl/libxl_dom_suspend.c | 8 +++-
> tools/libxl/libxl_internal.h | 2 +
> tools/libxl/libxl_types.idl | 1 +
> 5 files changed, 75 insertions(+), 37 deletions(-)
>
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 89fe80fc9c..bc4613a296 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -27,6 +27,64 @@
>
> #include <xen-xsm/flask/flask.h>
>
> +int libxl__domain_set_device_model(libxl__gc *gc, libxl_domain_config
> *d_config)
> +{
> + libxl_domain_build_info *b_info = &d_config->b_info;
> + int ret;
> +
> + libxl_defbool_setdefault(&b_info->device_model_stubdomain, false);
> +
> + if (b_info->device_model_version)
> + return 0;
> +
> + switch (b_info->type) {
> + case LIBXL_DOMAIN_TYPE_HVM:
> + if (libxl_defbool_val(b_info->device_model_stubdomain)) {
> + b_info->device_model_version =
> + LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL;
> + } else {
> + b_info->device_model_version = libxl__default_device_model(gc);
> + }
> + break;
> + default:
> + ret = libxl__need_xenpv_qemu(gc, d_config);
> + switch (ret) {
> + case 1:
> + d_config->b_info.device_model_version =
> + LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
> + break;
> + case 0:
> + d_config->b_info.device_model_version =
> + LIBXL_DEVICE_MODEL_VERSION_NONE_REQUIRED;
> + break;
> + default:
> + LOGE(ERROR, "Unable to determine QEMU requisite");
> + return ERROR_FAIL;
You could just return ret and propagate the error from the previous
function.
> + }
> + }
> +
> + if (b_info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN)
> {
> + const char *dm;
> +
> + dm = libxl__domain_device_model(gc, b_info);
> + ret = access(dm, X_OK);
> + if (ret < 0) {
> + /* qemu-xen unavailable, use qemu-xen-traditional */
> + if (errno == ENOENT) {
> + LOGE(INFO, "qemu-xen is unavailable"
> + ", using qemu-xen-traditional instead");
> + b_info->device_model_version =
> + LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL;
> + } else {
> + LOGE(ERROR, "qemu-xen access error");
> + return ERROR_FAIL;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> int libxl__domain_create_info_setdefault(libxl__gc *gc,
> libxl_domain_create_info *c_info)
> {
> @@ -80,45 +138,10 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
> return rc;
> }
>
> - libxl_defbool_setdefault(&b_info->device_model_stubdomain, false);
> -
> if (libxl_defbool_val(b_info->device_model_stubdomain) &&
> !b_info->device_model_ssidref)
> b_info->device_model_ssidref = SECINITSID_DOMDM;
>
> - if (!b_info->device_model_version) {
> - if (b_info->type == LIBXL_DOMAIN_TYPE_HVM) {
> - if (libxl_defbool_val(b_info->device_model_stubdomain)) {
> - b_info->device_model_version =
> - LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL;
> - } else {
> - b_info->device_model_version =
> libxl__default_device_model(gc);
> - }
> - } else {
> - b_info->device_model_version =
> - LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
> - }
> - if (b_info->device_model_version
> - == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
> - const char *dm;
> -
> - dm = libxl__domain_device_model(gc, b_info);
> - rc = access(dm, X_OK);
> - if (rc < 0) {
> - /* qemu-xen unavailable, use qemu-xen-traditional */
> - if (errno == ENOENT) {
> - LOGE(INFO, "qemu-xen is unavailable"
> - ", using qemu-xen-traditional instead");
> - b_info->device_model_version =
> - LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL;
> - } else {
> - LOGE(ERROR, "qemu-xen access error");
> - return ERROR_FAIL;
> - }
> - }
> - }
> - }
FTR I would have preferred a pre-patch that did the move of this chunk
of code into libxl__domain_set_device_model without any functional
change, and then a second patch that introduces the new functionality.
> -
> if (b_info->blkdev_start == NULL)
> b_info->blkdev_start = libxl__strdup(NOGC, "xvda");
>
> @@ -938,6 +961,12 @@ static void initiate_domain_create(libxl__egc *egc,
> goto error_out;
> }
>
> + ret = libxl__domain_set_device_model(gc, d_config);
> + if (ret) {
> + LOGD(ERROR, domid, "Unable to set domain device model");
> + goto error_out;
> + }
> +
> ret = libxl__domain_create_info_setdefault(gc, &d_config->c_info);
> if (ret) {
> LOGD(ERROR, domid, "Unable to set domain create info defaults");
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index 2f19786bdd..086e566311 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -2168,6 +2168,8 @@ void libxl__spawn_stub_dm(libxl__egc *egc,
> libxl__stub_dm_spawn_state *sdss)
> dm_config->c_info.run_hotplug_scripts =
> guest_config->c_info.run_hotplug_scripts;
>
> + ret = libxl__domain_set_device_model(gc, dm_config);
> + if (ret) goto out;
> ret = libxl__domain_create_info_setdefault(gc, &dm_config->c_info);
> if (ret) goto out;
> ret = libxl__domain_build_info_setdefault(gc, &dm_config->b_info);
> diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
> index d1af3a6573..c492fe5dd1 100644
> --- a/tools/libxl/libxl_dom_suspend.c
> +++ b/tools/libxl/libxl_dom_suspend.c
> @@ -379,7 +379,9 @@ static void
> domain_suspend_common_guest_suspended(libxl__egc *egc,
> libxl__ev_xswatch_deregister(gc, &dsps->guest_watch);
> libxl__ev_time_deregister(gc, &dsps->guest_timeout);
>
> - if (dsps->type == LIBXL_DOMAIN_TYPE_HVM) {
> + if (dsps->type == LIBXL_DOMAIN_TYPE_HVM ||
> + libxl__device_model_version_running(gc, dsps->domid) ==
> + LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
> dsps->callback_device_model_done = domain_suspend_common_done;
> libxl__domain_suspend_device_model(egc, dsps); /* must be last */
> return;
> @@ -459,7 +461,9 @@ int libxl__domain_resume(libxl__gc *gc, uint32_t domid,
> int suspend_cancel)
> goto out;
> }
>
> - if (type == LIBXL_DOMAIN_TYPE_HVM) {
> + if (type == LIBXL_DOMAIN_TYPE_HVM ||
> + libxl__device_model_version_running(gc, domid) ==
> + LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
> rc = libxl__domain_resume_device_model(gc, domid);
> if (rc) {
> LOGD(ERROR, domid, "failed to resume device model:%d", rc);
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 44e0221284..25f113404b 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -1374,6 +1374,8 @@ _hidden int libxl__device_nextid(libxl__gc *gc,
> uint32_t domid,
> _hidden int libxl__resolve_domid(libxl__gc *gc, const char *name,
> uint32_t *domid);
>
> +_hidden int libxl__domain_set_device_model(libxl__gc *gc,
> + libxl_domain_config *d_config);
> /*
> * For each aggregate type which can be used as an input we provide:
> *
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index cb4702fd7a..7d75bd3850 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -106,6 +106,7 @@ libxl_device_model_version =
> Enumeration("device_model_version", [
> (0, "UNKNOWN"),
> (1, "QEMU_XEN_TRADITIONAL"), # Historical qemu-xen device model (qemu-dm)
> (2, "QEMU_XEN"), # Upstream based qemu-xen device model
> + (3, "NONE_REQUIRED"),
Plain "NONE" would also be fine here IMO.
Thanks, Roger.
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