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

[Philippe Mathieu-Daudé <f4bug@xxxxxxxxx>]

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.

> +        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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