Re: [RFC PATCH v5 39/52] i386/xen: add monitor commands to test event injection

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* David Woodhouse (dwmw2@infradead.org) wrote:
> On Wed, 2023-01-04 at 12:48 +0000, Dr. David Alan Gilbert wrote:
> > * David Woodhouse (dwmw2@infradead.org) wrote:
> > > From: Joao Martins <joao.m.martins@oracle.com>
> > > 
> > > Specifically add listing, injection of event channels.
> > 
> > These are all for debug only aren't they?
> 
> Mostly. Injecting VIRQ_DEBUG into a guest is useful for debugging the
> guest too. Slightly inclined just to drop it as there's plenty of more
> useful things to implement, but let's have a go...

Note also, please put an x_ in the name (like qmp_x_query_ramblock)
to indicate that it's debug and you want the freedom to change the
structure/behaviour rather than carving the API in stone.

> > Even so, see docs/devel/writing-monitor-commands.rst, people like
> > commands to be built around qmp if possible now; there's a thing for
> > dumping text through it anyway for debug.
> 
> OK... something like this?

No; that's a bit of a mix:
The idea is that you either:
  a) Build the QMP with the data structure well defined like you've done
     and then make the HMP code monitor_printf that.

  b) Or you decide the data is mostly for debug and you can change it
when you like, and so the structure is unimportant; then you make the
  QMP side generate the HumanReadableText and just get the HMP side
  to print it.

An example of 'b' is qmp_x_query_ramblock' - note there's no actual HMP
code there and the qmp_x_query_ramblock is doing the HRT creation.

An example of 'a' is 'hmp_info_mice' which calls qmp_query_mice
and then prints it out.

Dave


> From ef1d7d08ee544921c056cc8f8c38bdd691cf71b4 Mon Sep 17 00:00:00 2001
> From: David Woodhouse <dwmw@amazon.co.uk>
> Date: Thu, 5 Jan 2023 19:34:15 +0000
> Subject: [PATCH] Convert xen-event-list to qmp
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>  hmp-commands.hx          |  2 +-
>  hw/i386/kvm/xen_evtchn.c | 70 +++++++++++++++++++++++++++++++++++-----
>  hw/i386/kvm/xen_evtchn.h |  4 ++-
>  qapi/misc.json           | 68 ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 134 insertions(+), 10 deletions(-)
> 
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index fd77c432c0..eac182307c 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1836,7 +1836,7 @@ ERST
>          .args_type  = "",
>          .params     = "",
>          .help       = "list event channel state",
> -        .cmd        = hmp_xen_event_list,
> +        .cmd_info_hrt = hmp_xen_event_list,
>      },
>  
>  SRST
> diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
> index c58237cdd2..ee50839804 100644
> --- a/hw/i386/kvm/xen_evtchn.c
> +++ b/hw/i386/kvm/xen_evtchn.c
> @@ -15,6 +15,7 @@
>  #include "qemu/main-loop.h"
>  #include "qemu/log.h"
>  #include "qapi/error.h"
> +#include "qapi/qapi-commands-misc.h"
>  #include "qom/object.h"
>  #include "exec/target_page.h"
>  #include "exec/address-spaces.h"
> @@ -1539,21 +1540,22 @@ static const char *type_names[] = {
>      "ipi"
>  };
>  
> -void hmp_xen_event_list(Monitor *mon, const QDict *qdict)
> +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) {
> -        monitor_printf(mon, "Xen event channel emulation not enabled\n");
> -        return;
> +        error_setg(errp, "Xen event channel emulation not enabled\n");
> +        return NULL;
>      }
>  
>      shinfo = xen_overlay_get_shinfo_ptr();
>      if (!shinfo) {
> -        monitor_printf(mon, "Xen shared info page not allocated\n");
> -        return;
> +        error_setg(errp, "Xen shared info page not allocated\n");
> +        return NULL;
>      }
>      if (xen_is_long_mode()) {
>          pending = shinfo + offsetof(struct shared_info, evtchn_pending);
> @@ -1567,17 +1569,69 @@ void hmp_xen_event_list(Monitor *mon, const QDict *qdict)
>  
>      for (i = 0; i < s->nr_ports; i++) {
>          XenEvtchnPort *p = &s->port_table[i];
> +        EvtchnInfo *info;
>  
>          if (p->type == EVTCHNSTAT_closed) {
>              continue;
>          }
>  
> -        monitor_printf(mon, "port %4u %s/%d vcpu:%d pending:%d mask:%d\n", i,
> -                       type_names[p->type], p->type_val, p->vcpu,
> -                       test_bit(i, pending), test_bit(i, mask));
> +        info = g_new0(EvtchnInfo, 1);
> +
> +        info->port = i;
> +        info->type = g_strdup(type_names[p->type]);
> +        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);
>      }
>  
>      qemu_mutex_unlock(&s->port_lock);
> +
> +    return head;
> +}
> +
> +HumanReadableText *hmp_xen_event_list(Error **errp)
> +{
> +    EvtchnInfoList *iter, *info_list;
> +    g_autoptr(GString) buf = g_string_new("");
> +
> +
> +    info_list = qmp_xen_event_list(errp);
> +    if (*errp) {
> +        return NULL;
> +    }
> +
> +    for (iter = info_list; iter; iter = iter->next) {
> +        EvtchnInfo *info = iter->value;
> +
> +        g_string_append_printf(buf, "port %4lu: %s", info->port, info->type);
> +        if (strcmp(info->type, "ipi")) {
> +            g_string_append_printf(buf,  "(");
> +            if (info->remote_domain) {
> +                g_string_append_printf(buf, "%s:", info->remote_domain);
> +            }
> +            g_string_append_printf(buf, "%ld)", info->target);
> +        }
> +        g_string_append_printf(buf, " vcpu:%ld", info->vcpu);
> +        if (info->pending) {
> +            g_string_append_printf(buf, " PENDING");
> +        }
> +        if (info->masked) {
> +            g_string_append_printf(buf, " MASKED");
> +        }
> +        g_string_append_printf(buf, "\n");
> +    }
> +
> +    qapi_free_EvtchnInfoList(info_list);
> +    return human_readable_text_from_str(buf);
>  }
>  
>  void hmp_xen_event_inject(Monitor *mon, const QDict *qdict)
> diff --git a/hw/i386/kvm/xen_evtchn.h b/hw/i386/kvm/xen_evtchn.h
> index 146c504773..1d1ca64e6f 100644
> --- a/hw/i386/kvm/xen_evtchn.h
> +++ b/hw/i386/kvm/xen_evtchn.h
> @@ -12,6 +12,8 @@
>  #ifndef QEMU_XEN_EVTCHN_H
>  #define QEMU_XEN_EVTCHN_H
>  
> +#include "qapi/type-helpers.h"
> +
>  #include "hw/sysbus.h"
>  
>  typedef uint32_t evtchn_port_t;
> @@ -42,8 +44,8 @@ int xen_be_evtchn_pending(struct xenevtchn_handle *xc);
>  /* Apart from this which is a local addition */
>  int xen_be_evtchn_get_guest_port(struct xenevtchn_handle *xc);
>  
> -void hmp_xen_event_list(Monitor *mon, const QDict *qdict);
>  void hmp_xen_event_inject(Monitor *mon, const QDict *qdict);
> +HumanReadableText *hmp_xen_event_list(Error **errp);
>  
>  struct evtchn_status;
>  struct evtchn_close;
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 27ef5a2b20..5c0f53cbc7 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -584,3 +584,70 @@
>  { '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
> +#
> +# @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
> +##
> +{ 'struct': 'EvtchnInfo',
> +  'data': {'port': 'int',
> +	   'type': 'str',
> +	   'remote-domain': 'str',
> +	   'vcpu': 'int',
> +	   '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": "",
> +#             "masked": false,
> +#             "type": "virq",
> +#             "target": 0
> +#         }
> +#      ]
> +#    }
> +#
> +##
> +{ 'command': 'xen-event-list',
> +  'returns': ['EvtchnInfo'] }
> -- 
> 2.34.1
> 
> 


-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK