Re: [Xen-devel] [Qemu-devel] [PATCH] xen: use libxendevice model to restrict operations

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Philippe Mathieu-Daudé [mailto:philippe.mathieu.daude@xxxxxxxxx]
> On Behalf Of Philippe Mathieu-Daudé
> Sent: 17 March 2017 21:21
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; qemu-devel@xxxxxxxxxx; xen-
> devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>; Paolo Bonzini
> <pbonzini@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Subject: Re: [Qemu-devel] [PATCH] xen: use libxendevice model to restrict
> operations
> 
> Hi Paul,
> 
> On 03/17/2017 10:30 AM, Paul Durrant wrote:
> > This patch adds a command-line option (-xen-domid-restrict) which will
> > use the new libxendevicemodel API to restrict devicemodel operations to
> > the specified domid.
> >
> > This patch also adds a tracepoint to allow successful enabling of the
> > restriction to be monitored.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > ---
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >
> > NOTE: This is already re-based on Juergen Gross's patch "xen: use 5 digit
> >       xen versions" and so should not be applied until after that patch
> >       has been applied.
> > ---
> >  hw/xen/trace-events         |  1 +
> >  include/hw/xen/xen.h        |  1 +
> >  include/hw/xen/xen_common.h | 23 +++++++++++++++++++++++
> >  qemu-options.hx             |  6 ++++++
> >  vl.c                        |  8 ++++++++
> >  xen-hvm.c                   |  8 ++++++++
> >  6 files changed, 47 insertions(+)
> >
> > diff --git a/hw/xen/trace-events b/hw/xen/trace-events
> > index c4fb6f1..a5b5e8b 100644
> > --- a/hw/xen/trace-events
> > +++ b/hw/xen/trace-events
> > @@ -11,3 +11,4 @@ xen_map_portio_range(uint32_t id, uint64_t
> start_addr, uint64_t end_addr) "id: %
> >  xen_unmap_portio_range(uint32_t id, uint64_t start_addr, uint64_t
> end_addr) "id: %u start: %#"PRIx64" end: %#"PRIx64
> >  xen_map_pcidev(uint32_t id, uint8_t bus, uint8_t dev, uint8_t func) "id:
> %u bdf: %02x.%02x.%02x"
> >  xen_unmap_pcidev(uint32_t id, uint8_t bus, uint8_t dev, uint8_t func) "id:
> %u bdf: %02x.%02x.%02x"
> > +xen_domid_restrict(void) ""
> > diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
> > index 2b1733b..7efcdaa 100644
> > --- a/include/hw/xen/xen.h
> > +++ b/include/hw/xen/xen.h
> > @@ -21,6 +21,7 @@ enum xen_mode {
> >
> >  extern uint32_t xen_domid;
> >  extern enum xen_mode xen_mode;
> > +extern bool xen_domid_restrict;
> >
> >  extern bool xen_allowed;
> >
> > diff --git a/include/hw/xen/xen_common.h
> b/include/hw/xen/xen_common.h
> > index df098c7..5962bc4 100644
> > --- a/include/hw/xen/xen_common.h
> > +++ b/include/hw/xen/xen_common.h
> > @@ -152,6 +152,13 @@ static inline int xendevicemodel_set_mem_type(
> >      return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
> >  }
> >
> > +static inline int xendevicemodel_restrict(
> > +    xendevicemodel_handle *dmod, domid_t domid)
> > +{
> > +    errno = ENOTTY;
> > +    return -1;
> > +}
> > +
> >  #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
> >
> >  #include <xendevicemodel.h>
> > @@ -206,6 +213,22 @@ static inline int xen_modified_memory(domid_t
> domid, uint64_t first_pfn,
> >      return xendevicemodel_modified_memory(xen_dmod, domid,
> first_pfn, nr);
> >  }
> >
> > +static inline int xen_restrict(domid_t domid)
> > +{
> > +    int rc = xendevicemodel_restrict(xen_dmod, domid);
> 
> might it be more useful to log the retcode?
> 
>         trace_xen_domid_restrict(rc);
> 
> > +
> > +    if (rc == 0) {
> > +        trace_xen_domid_restrict();
> 
> and drop the previous line.

Actually the retcode is pretty uninteresting but tracing errno would be a good 
idea so I think I'll do that.

Cheers,

  Paul

> 
> > +        return 0;
> > +    }
> > +
> > +    if (errno == ENOTTY) {
> > +        return 0;
> > +    }
> > +
> > +    return rc;
> > +}
> > +
> >  /* Xen 4.2 through 4.6 */
> >  #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
> >
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 99af8ed..4aab077 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -3354,6 +3354,10 @@ DEF("xen-attach", 0,
> QEMU_OPTION_xen_attach,
> >      "-xen-attach     attach to existing xen domain\n"
> >      "                xend will use this when starting QEMU\n",
> >      QEMU_ARCH_ALL)
> > +DEF("xen-domid-restrict", 0, QEMU_OPTION_xen_domid_restrict,
> > +    "-xen-domid-restrict     restrict set of available xen operations\n"
> > +    "                        to specified domain id\n",
> > +    QEMU_ARCH_ALL)
> >  STEXI
> >  @item -xen-domid @var{id}
> >  @findex -xen-domid
> > @@ -3366,6 +3370,8 @@ Warning: should not be used when xend is in use
> (XEN only).
> >  @findex -xen-attach
> >  Attach to existing xen domain.
> >  xend will use this when starting QEMU (XEN only).
> > +@findex -xen-domid-restrict
> > +Restrict set of available xen operations to specified domain id (XEN only).
> >  ETEXI
> >
> >  DEF("no-reboot", 0, QEMU_OPTION_no_reboot, \
> > diff --git a/vl.c b/vl.c
> > index 0b4ed52..f46e070 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -205,6 +205,7 @@ static NotifierList machine_init_done_notifiers =
> >  bool xen_allowed;
> >  uint32_t xen_domid;
> >  enum xen_mode xen_mode = XEN_EMULATE;
> > +bool xen_domid_restrict;
> >
> >  static int has_defaults = 1;
> >  static int default_serial = 1;
> > @@ -3933,6 +3934,13 @@ int main(int argc, char **argv, char **envp)
> >                  }
> >                  xen_mode = XEN_ATTACH;
> >                  break;
> > +            case QEMU_OPTION_xen_domid_restrict:
> > +                if (!(xen_available())) {
> > +                    error_report("Option not supported for this target");
> > +                    exit(1);
> > +                }
> > +                xen_domid_restrict = true;
> > +                break;
> >              case QEMU_OPTION_trace:
> >                  g_free(trace_file);
> >                  trace_file = trace_opt_parse(optarg);
> > diff --git a/xen-hvm.c b/xen-hvm.c
> > index 4b928cf..335e263 100644
> > --- a/xen-hvm.c
> > +++ b/xen-hvm.c
> > @@ -1226,6 +1226,14 @@ void xen_hvm_init(PCMachineState *pcms,
> MemoryRegion **ram_memory)
> >          goto err;
> >      }
> >
> > +    if (xen_domid_restrict) {
> > +        rc = xen_restrict(xen_domid);
> > +        if (rc < 0) {
> > +            error_report("failed to restrict: error %d", errno);
> > +            goto err;
> > +        }
> > +    }
> > +
> >      xen_create_ioreq_server(xen_domid, &state->ioservid);
> >
> >      state->exit.notify = xen_exit_notifier;
> >

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