Re: [PATCH v7 38/51] i386/xen: add monitor commands to test event injection

[Markus Armbruster <armbru@redhat.com>]

David Woodhouse <dwmw2@infradead.org> writes:

> From: Joao Martins <joao.m.martins@oracle.com>
>
> Specifically add listing, injection of event channels.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  hmp-commands.hx          |  29 ++++++++
>  hw/i386/kvm/meson.build  |   4 ++
>  hw/i386/kvm/xen-stubs.c  |  25 +++++++
>  hw/i386/kvm/xen_evtchn.c | 138 +++++++++++++++++++++++++++++++++++++++
>  hw/i386/kvm/xen_evtchn.h |   3 +
>  monitor/misc.c           |   4 ++
>  qapi/misc.json           |  91 ++++++++++++++++++++++++++
>  7 files changed, 294 insertions(+)
>  create mode 100644 hw/i386/kvm/xen-stubs.c
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 673e39a697..fd77c432c0 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1815,3 +1815,32 @@ SRST
>    Dump the FDT in dtb format to *filename*.
>  ERST
>  #endif
> +
> +#if defined(CONFIG_XEN_EMU)
> +    {
> +        .name       = "xen-event-inject",
> +        .args_type  = "port:i",
> +        .params     = "port",
> +        .help       = "inject event channel",
> +        .cmd        = hmp_xen_event_inject,
> +    },
> +
> +SRST
> +``xen-event-inject`` *port*
> +  Notify guest via event channel on port *port*.
> +ERST
> +
> +
> +    {
> +        .name       = "xen-event-list",
> +        .args_type  = "",
> +        .params     = "",
> +        .help       = "list event channel state",
> +        .cmd        = hmp_xen_event_list,
> +    },
> +
> +SRST
> +``xen-event-list``
> +  List event channels in the guest
> +ERST
> +#endif
> diff --git a/hw/i386/kvm/meson.build b/hw/i386/kvm/meson.build
> index cab64df339..577eb50a18 100644
> --- a/hw/i386/kvm/meson.build
> +++ b/hw/i386/kvm/meson.build
> @@ -10,3 +10,7 @@ i386_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files(
>    ))
>  
>  i386_ss.add_all(when: 'CONFIG_KVM', if_true: i386_kvm_ss)
> +
> +specific_ss.add(when: 'CONFIG_XEN_EMU', if_false: files(
> +  'xen-stubs.c',
> +))
> diff --git a/hw/i386/kvm/xen-stubs.c b/hw/i386/kvm/xen-stubs.c
> new file mode 100644
> index 0000000000..6f433dc995
> --- /dev/null
> +++ b/hw/i386/kvm/xen-stubs.c
> @@ -0,0 +1,25 @@
> +/*
> + * QEMU Xen emulation: QMP stubs
> + *
> + * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
> + *
> + * Authors: David Woodhouse <dwmw2@infradead.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qapi/qapi-commands-misc.h"
> +
> +EvtchnInfoList *qmp_xen_event_list(Error **errp)
> +{
> +    error_setg(errp, "Xen event channel emulation not enabled");
> +    return NULL;
> +}
> +
> +void qmp_xen_event_inject(uint32_t port, Error **errp)
> +{
> +    error_setg(errp, "Xen event channel emulation not enabled");
> +}
> diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
> index 6b6df39978..a73db5d2bc 100644
> --- a/hw/i386/kvm/xen_evtchn.c
> +++ b/hw/i386/kvm/xen_evtchn.c
> @@ -14,7 +14,11 @@
>  #include "qemu/module.h"
>  #include "qemu/main-loop.h"
>  #include "qemu/log.h"
> +#include "monitor/monitor.h"
> +#include "monitor/hmp.h"
>  #include "qapi/error.h"
> +#include "qapi/qapi-commands-misc.h"
> +#include "qapi/qmp/qdict.h"
>  #include "qom/object.h"
>  #include "exec/target_page.h"
>  #include "exec/address-spaces.h"
> @@ -1059,3 +1063,137 @@ int xen_evtchn_send_op(struct evtchn_send *send)
>      return ret;
>  }
>  
> +static const char *type_names[] = {
> +    "closed",
> +    "unbound",
> +    "interdomain",
> +    "pirq",
> +    "virq",
> +    "ipi"
> +};
> +
> +EvtchnInfoList *qmp_xen_event_list(Error **errp)
> +{
> +    XenEvtchnState *s = xen_evtchn_singleton;
> +    EvtchnInfoList *head = NULL, **tail = &head;
> +    void *shinfo, *pending, *mask;
> +    int i;
> +
> +    if (!s) {
> +        error_setg(errp, "Xen event channel emulation not enabled");
> +        return NULL;
> +    }
> +
> +    shinfo = xen_overlay_get_shinfo_ptr();
> +    if (!shinfo) {
> +        error_setg(errp, "Xen shared info page not allocated");
> +        return NULL;
> +    }

Suggest a blank line here.

> +    if (xen_is_long_mode()) {
> +        pending = shinfo + offsetof(struct shared_info, evtchn_pending);
> +        mask = shinfo + offsetof(struct shared_info, evtchn_mask);
> +    } else {
> +        pending = shinfo + offsetof(struct compat_shared_info, evtchn_pending);
> +        mask = shinfo + offsetof(struct compat_shared_info, evtchn_mask);
> +    }
> +
> +    QEMU_LOCK_GUARD(&s->port_lock);
> +
> +    for (i = 0; i < s->nr_ports; i++) {
> +        XenEvtchnPort *p = &s->port_table[i];
> +        EvtchnInfo *info;
> +
> +        if (p->type == EVTCHNSTAT_closed) {
> +            continue;
> +        }
> +
> +        info = g_new0(EvtchnInfo, 1);
> +
> +        info->port = i;
> +        info->type = g_strdup(type_names[p->type]);

What ensures p->type is in bounds?

> +        if (p->type == EVTCHNSTAT_interdomain) {
> +            info->remote_domain = g_strdup((p->type_val & PORT_INFO_TYPEVAL_REMOTE_QEMU) ?
> +                                           "qemu" : "loopback");
> +            info->target = p->type_val & PORT_INFO_TYPEVAL_REMOTE_PORT_MASK;
> +        } else {
> +            info->target = p->type_val;
> +        }
> +        info->vcpu = p->vcpu;
> +        info->pending = test_bit(i, pending);
> +        info->masked = test_bit(i, mask);
> +
> +        QAPI_LIST_APPEND(tail, info);
> +    }
> +
> +    return head;
> +}
> +
> +void qmp_xen_event_inject(uint32_t port, Error **errp)
> +{
> +    XenEvtchnState *s = xen_evtchn_singleton;
> +
> +    if (!s) {
> +        error_setg(errp, "Xen event channel emulation not enabled");
> +        return;
> +    }
> +
> +    if (!valid_port(port)) {
> +        error_setg(errp, "Invalid port %u", port);
> +    }
> +
> +    QEMU_LOCK_GUARD(&s->port_lock);
> +
> +    if (set_port_pending(s, port)) {
> +        error_setg(errp, "Failed to set port %u", port);
> +        return;
> +    }
> +}
> +
> +void hmp_xen_event_list(Monitor *mon, const QDict *qdict)
> +{
> +    EvtchnInfoList *iter, *info_list;
> +    Error *err = NULL;
> +
> +    info_list = qmp_xen_event_list(&err);
> +    if (err) {
> +        hmp_handle_error(mon, err);
> +        return;
> +    }
> +
> +    for (iter = info_list; iter; iter = iter->next) {
> +        EvtchnInfo *info = iter->value;
> +
> +        monitor_printf(mon, "port %4lu: vcpu: %ld %s", info->port, info->vcpu,
> +                       info->type);
> +        if (strcmp(info->type, "ipi")) {
> +            monitor_printf(mon,  "(");
> +            if (info->remote_domain) {
> +                monitor_printf(mon, "%s:", info->remote_domain);
> +            }
> +            monitor_printf(mon, "%ld)", info->target);
> +        }
> +        if (info->pending) {
> +            monitor_printf(mon, " PENDING");
> +        }
> +        if (info->masked) {
> +            monitor_printf(mon, " MASKED");
> +        }
> +        monitor_printf(mon, "\n");
> +    }
> +
> +    qapi_free_EvtchnInfoList(info_list);
> +}
> +
> +void hmp_xen_event_inject(Monitor *mon, const QDict *qdict)
> +{
> +    int port = qdict_get_int(qdict, "port");
> +    Error *err = NULL;
> +
> +    qmp_xen_event_inject(port, &err);
> +    if (err) {
> +        hmp_handle_error(mon, err);
> +    } else {
> +        monitor_printf(mon, "Delivered port %d\n", port);
> +    }
> +}
> +

In general, I prefer to keep HMP commands separate, say in
i386-kvm-hmp-cmds.c.  Not sure it's worth the trouble here.

> diff --git a/hw/i386/kvm/xen_evtchn.h b/hw/i386/kvm/xen_evtchn.h
> index 5d3e03553f..670f8b3f7d 100644
> --- a/hw/i386/kvm/xen_evtchn.h
> +++ b/hw/i386/kvm/xen_evtchn.h
> @@ -16,6 +16,9 @@ void xen_evtchn_create(void);
>  int xen_evtchn_soft_reset(void);
>  int xen_evtchn_set_callback_param(uint64_t param);
>  
> +void hmp_xen_event_inject(Monitor *mon, const QDict *qdict);
> +void hmp_xen_event_list(Monitor *mon, const QDict *qdict);
> +

Have you considered include/monitor/hmp.h?

>  struct evtchn_status;
>  struct evtchn_close;
>  struct evtchn_unmask;
> diff --git a/monitor/misc.c b/monitor/misc.c
> index bf3f1c67ca..7d8c473ffb 100644
> --- a/monitor/misc.c
> +++ b/monitor/misc.c
> @@ -82,6 +82,10 @@
>  /* Make devices configuration available for use in hmp-commands*.hx templates */
>  #include CONFIG_DEVICES
>  
> +#ifdef CONFIG_XEN_EMU
> +#include "hw/i386/kvm/xen_evtchn.h"
> +#endif
> +

Uh... what for?

>  /* file descriptors passed via SCM_RIGHTS */
>  typedef struct mon_fd_t mon_fd_t;
>  struct mon_fd_t {
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 27ef5a2b20..6284f86a5b 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -584,3 +584,94 @@
>  { 'event': 'VFU_CLIENT_HANGUP',
>    'data': { 'vfu-id': 'str', 'vfu-qom-path': 'str',
>              'dev-id': 'str', 'dev-qom-path': 'str' } }
> +
> +##
> +# @EvtchnInfo:
> +#
> +# Information about a Xen event channel port
> +#
> +# @port: the port number
> +#
> +# @vcpu: target vCPU for this port
> +#
> +# @type: the port type
> +#
> +# @remote-domain: remote domain for interdomain ports
> +#
> +# @target: remote port ID, or virq/pirq number
> +#
> +# @pending: port is currently active pending delivery
> +#
> +# @masked: port is masked
> +#
> +# Since: x.xx

"Since: 8.0.0" (with any luck).  More of the same below.

> +##
> +{ 'struct': 'EvtchnInfo',
> +  'data': {'port': 'int',
> +	   'vcpu': 'int',
> +	   'type': 'str',

Could we make this a QAPI enum?

> +	   'remote-domain': 'str',
> +	   'target': 'int',
> +	   'pending': 'bool',
> +	   'masked': 'bool'}}
> +
> +
> +##
> +# @xen-event-list:
> +#
> +# Query the Xen event channels opened by the guest.
> +#
> +# Returns: list of open event channel ports.
> +#
> +# Since: x.xx
> +#
> +# Example:
> +#
> +# -> { "execute": "xen-event-list" }
> +# <- { "return": [
> +#         {
> +#             "pending": false,
> +#             "port": 1,
> +#             "vcpu": 1,
> +#             "remote-domain": "qemu",
> +#             "masked": false,
> +#             "type": "interdomain",
> +#             "target": 1
> +#         },
> +#         {
> +#             "pending": false,
> +#             "port": 2,
> +#             "vcpu": 0,
> +#             "remote-domain": "",

Uh, "" is possible?  @remote-domain's doc string didn't prepare me for
that.  What does it mean?

> +#             "masked": false,
> +#             "type": "virq",
> +#             "target": 0
> +#         }
> +#      ]
> +#    }
> +#
> +##
> +{ 'command': 'xen-event-list',
> +  'returns': ['EvtchnInfo']
> +}
> +
> +##
> +# @xen-event-inject:
> +#
> +# Inject a Xen event channel port to the guest.

Would it be useful to explain what it means to "inject a Xen event
channel port to the guest"?  I have no idea, but perhaps we believe
interested in this command should be able to explain it in their sleep.

> +#
> +# @port: The port number
> +#
> +# Returns: - Nothing on success.
> +#
> +# Since: x.xx
> +#
> +# Example:
> +#
> +# -> { "execute": "xen-event-inject", "arguments": { "port": 1 } }
> +# <- { "return": { } }
> +#
> +##
> +{ 'command': 'xen-event-inject',
> +  'data': { 'port': 'uint32' }
> +}

Did you consider 'if': 'CONFIG_XEN'?

Hmm, it's target-dependent, so it would have to go into
misc-target.json.  qmp_xen_event_inject() then needs target-dependent
header qapi/qapi-commands-misc-target.h.  Fine if it's in a
target-dependent .c anyway.  Else it could be more trouble than it's
worth.