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Re: [PATCH v3 01/10] qdev/qbus: add hidden device support
From: |
Alex Williamson |
Subject: |
Re: [PATCH v3 01/10] qdev/qbus: add hidden device support |
Date: |
Tue, 15 Oct 2019 13:19:33 -0600 |
On Fri, 11 Oct 2019 13:20:06 +0200
Jens Freimann <address@hidden> wrote:
> This adds support for hiding a device to the qbus and qdev APIs. The
> first user of this will be the virtio-net failover feature but the API
> introduced with this patch could be used to implement other features as
> well, for example hiding pci devices when a pci bus is powered off.
>
> qdev_device_add() is modified to check for a net_failover_pair_id
> argument in the option string. A DeviceListener callback
> should_be_hidden() is added. It can be used by a standby device to
> inform qdev that this device should not be added now. The standby device
> handler can store the device options to plug the device in at a later
> point in time.
>
> One reason for hiding the device is that we don't want to expose both
> devices to the guest kernel until the respective virtio feature bit
> VIRTIO_NET_F_STANDBY was negotiated and we know that the devices will be
> handled correctly by the guest.
>
> More information on the kernel feature this is using:
> https://www.kernel.org/doc/html/latest/networking/net_failover.html
>
> An example where the primary device is a vfio-pci device and the standby
> device is a virtio-net device:
>
> A device is hidden when it has an "net_failover_pair_id" option, e.g.
>
> -device virtio-net-pci,...,failover=on,...
> -device vfio-pci,...,net_failover_pair_id=net1,...
>
> Signed-off-by: Jens Freimann <address@hidden>
> ---
> hw/core/qdev.c | 19 +++++++++++++++++++
> include/hw/qdev-core.h | 9 +++++++++
> qdev-monitor.c | 43 ++++++++++++++++++++++++++++++++++++++----
> vl.c | 6 ++++--
> 4 files changed, 71 insertions(+), 6 deletions(-)
>
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index cbad6c1d55..84fac591ca 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -212,6 +212,25 @@ void device_listener_unregister(DeviceListener *listener)
> QTAILQ_REMOVE(&device_listeners, listener, link);
> }
>
> +bool qdev_should_hide_device(QemuOpts *opts, Error **errp)
> +{
> + bool res = false;
> + bool match_found = false;
> + DeviceListener *listener;
> +
> + QTAILQ_FOREACH(listener, &device_listeners, link) {
> + if (listener->should_be_hidden) {
> + listener->should_be_hidden(listener, opts, &match_found, &res);
> + }
> +
> + if (match_found) {
> + break;
> + }
Calling convention here seems overly complicated, couldn't
should_be_hidden() just return >0 (should be hidden), 0 (should not be
hidden), <0 (don't care), ie. continue until >=0? The errp arg is
unused and using "res" to return should/shouldn't hide is very unclear.
The virtio callback renames this to hide, which makes more sense, but
as above, both the stop and hidden state could be conveyed with a
simple int return value. Thanks,
Alex
> + }
> +
> + return res;
> +}
> +
> void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
> int required_for_version)
> {
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index aa123f88cb..b61cf82ded 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -154,6 +154,13 @@ struct DeviceState {
> struct DeviceListener {
> void (*realize)(DeviceListener *listener, DeviceState *dev);
> void (*unrealize)(DeviceListener *listener, DeviceState *dev);
> + /*
> + * This callback is called just upon init of the DeviceState
> + * and can be used by a standby device for informing qdev if this
> + * device should be hidden by checking the device opts
> + */
> + void (*should_be_hidden)(DeviceListener *listener, QemuOpts *device_opts,
> + bool *match_found, bool *res);
> QTAILQ_ENTRY(DeviceListener) link;
> };
>
> @@ -451,4 +458,6 @@ static inline bool qbus_is_hotpluggable(BusState *bus)
> void device_listener_register(DeviceListener *listener);
> void device_listener_unregister(DeviceListener *listener);
>
> +bool qdev_should_hide_device(QemuOpts *opts, Error **errp);
> +
> #endif
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 148df9cacf..9fc8331157 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -32,9 +32,11 @@
> #include "qemu/help_option.h"
> #include "qemu/option.h"
> #include "qemu/qemu-print.h"
> +#include "qemu/option_int.h"
> #include "sysemu/block-backend.h"
> #include "sysemu/sysemu.h"
> #include "migration/misc.h"
> +#include "migration/migration.h"
>
> /*
> * Aliases were a bad idea from the start. Let's keep them
> @@ -562,14 +564,45 @@ void qdev_set_id(DeviceState *dev, const char *id)
> }
> }
>
> +static int is_failover_device(void *opaque, const char *name, const char
> *value,
> + Error **errp)
> +{
> + if (strcmp(name, "net_failover_pair_id") == 0) {
> + QemuOpts *opts = (QemuOpts *)opaque;
> +
> + if (qdev_should_hide_device(opts, errp) && errp && !*errp) {
> + return 1;
> + } else if (errp && *errp) {
> + return -1;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static bool should_hide_device(QemuOpts *opts, Error **err)
> +{
> + if (qemu_opt_foreach(opts, is_failover_device, opts, err) == 0) {
> + return false;
> + }
> + return true;
> +}
> +
> DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
> {
> DeviceClass *dc;
> const char *driver, *path;
> - DeviceState *dev;
> + DeviceState *dev = NULL;
> BusState *bus = NULL;
> Error *err = NULL;
>
> + if (opts && should_hide_device(opts, &err)) {
> + if (err) {
> + goto err_del_dev;
> + }
> + return NULL;
> + }
> +
> driver = qemu_opt_get(opts, "driver");
> if (!driver) {
> error_setg(errp, QERR_MISSING_PARAMETER, "driver");
> @@ -648,8 +681,10 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error
> **errp)
>
> err_del_dev:
> error_propagate(errp, err);
> - object_unparent(OBJECT(dev));
> - object_unref(OBJECT(dev));
> + if (dev) {
> + object_unparent(OBJECT(dev));
> + object_unref(OBJECT(dev));
> + }
> return NULL;
> }
>
> @@ -818,7 +853,7 @@ void qdev_unplug(DeviceState *dev, Error **errp)
> return;
> }
>
> - if (!migration_is_idle()) {
> + if (!migration_is_idle() && !migration_in_setup(migrate_get_current())) {
> error_setg(errp, "device_del not allowed while migrating");
> return;
> }
> diff --git a/vl.c b/vl.c
> index 002bf4919e..898b9901c8 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2204,10 +2204,12 @@ static int device_init_func(void *opaque, QemuOpts
> *opts, Error **errp)
> DeviceState *dev;
>
> dev = qdev_device_add(opts, errp);
> - if (!dev) {
> + if (!dev && *errp) {
> + error_report_err(*errp);
> return -1;
> + } else if (dev) {
> + object_unref(OBJECT(dev));
> }
> - object_unref(OBJECT(dev));
> return 0;
> }
>
- [PATCH v3 0/10] add failover feature for assigned network devices, Jens Freimann, 2019/10/11
- [PATCH v3 01/10] qdev/qbus: add hidden device support, Jens Freimann, 2019/10/11
- [PATCH v3 02/10] pci: mark devices partially unplugged, Jens Freimann, 2019/10/11
- [PATCH v3 03/10] pci: mark device having guest unplug request pending, Jens Freimann, 2019/10/11
- [PATCH v3 04/10] qapi: add unplug primary event, Jens Freimann, 2019/10/11
- [PATCH v3 05/10] qapi: add failover negotiated event, Jens Freimann, 2019/10/11
- [PATCH v3 06/10] migration: allow unplug during migration for failover devices, Jens Freimann, 2019/10/11
- [PATCH v3 07/10] migration: add new migration state wait-unplug, Jens Freimann, 2019/10/11