diff mbox

[v7,05/15] libxl: Load guest BIOS from file

Message ID 20160728105013.22310-6-anthony.perard@citrix.com (mailing list archive)
State New, archived
Headers show

Commit Message

Anthony PERARD July 28, 2016, 10:50 a.m. UTC
The path to the BIOS blob can be overriden by the xl's
bios_path_override option, or provided by u.hvm.bios_firmware in the
domain_build_info struct by other libxl user.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

---
Changes in V6:
- use goto for error handling of libxl__load_hvm_firmware_module()

Changes in V5:
- man page, use B<> to highlight config option in description.
- rename config option from `bios_override` to `bios_path_override`
- store libxl_read_file_contents() return value into r instead of e
  (just renamed the variable)
- rename domain_build_info.u.hvm.bios_firmware to system_firmware

Changes in V4:
- updating man page to have bios_override described.
- return ERROR_INVAL in libxl__load_hvm_firmware_module when the file is
  empty.

Changes in V3:
- move seabios_path and ovmf_path to libxl_path.c (with renaming)
- fix some coding style
- warn for empty file
- remove rombios stuff (will still be built-in hvmloader)
- rename field bios_filename in domain_build_info to bios_firmware to
  follow naming of acpi and smbios.
- log an error after libxl_read_file_contents() only when it return ENOENT
- return an error on empty file.
- added #define LIBXL_HAVE_BUILDINFO_HVM_BIOS_FIRMWARE
---
 docs/man/xl.cfg.pod.5.in     |  9 +++++++
 tools/libxl/libxl.h          |  8 ++++++
 tools/libxl/libxl_dom.c      | 61 ++++++++++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |  2 ++
 tools/libxl/libxl_paths.c    | 10 ++++++++
 tools/libxl/libxl_types.idl  |  1 +
 tools/libxl/xl_cmdimpl.c     | 11 +++++---
 7 files changed, 99 insertions(+), 3 deletions(-)

Comments

Shannon Zhao Aug. 15, 2016, 9:04 a.m. UTC | #1
On 2016/7/28 18:50, Anthony PERARD wrote:
> The path to the BIOS blob can be overriden by the xl's
> bios_path_override option, or provided by u.hvm.bios_firmware in the
> domain_build_info struct by other libxl user.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> Acked-by: Wei Liu <wei.liu2@citrix.com>
> 
> ---
> Changes in V6:
> - use goto for error handling of libxl__load_hvm_firmware_module()
> 
> Changes in V5:
> - man page, use B<> to highlight config option in description.
> - rename config option from `bios_override` to `bios_path_override`
> - store libxl_read_file_contents() return value into r instead of e
>   (just renamed the variable)
> - rename domain_build_info.u.hvm.bios_firmware to system_firmware
> 
> Changes in V4:
> - updating man page to have bios_override described.
> - return ERROR_INVAL in libxl__load_hvm_firmware_module when the file is
>   empty.
> 
> Changes in V3:
> - move seabios_path and ovmf_path to libxl_path.c (with renaming)
> - fix some coding style
> - warn for empty file
> - remove rombios stuff (will still be built-in hvmloader)
> - rename field bios_filename in domain_build_info to bios_firmware to
>   follow naming of acpi and smbios.
> - log an error after libxl_read_file_contents() only when it return ENOENT
> - return an error on empty file.
> - added #define LIBXL_HAVE_BUILDINFO_HVM_BIOS_FIRMWARE
> ---
>  docs/man/xl.cfg.pod.5.in     |  9 +++++++
>  tools/libxl/libxl.h          |  8 ++++++
>  tools/libxl/libxl_dom.c      | 61 ++++++++++++++++++++++++++++++++++++++++++++
>  tools/libxl/libxl_internal.h |  2 ++
>  tools/libxl/libxl_paths.c    | 10 ++++++++
>  tools/libxl/libxl_types.idl  |  1 +
>  tools/libxl/xl_cmdimpl.c     | 11 +++++---
>  7 files changed, 99 insertions(+), 3 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
> index 3bb27d0..a685b83 100644
> --- a/docs/man/xl.cfg.pod.5.in
> +++ b/docs/man/xl.cfg.pod.5.in
> @@ -1212,6 +1212,15 @@ Requires device_model_version=qemu-xen.
>  
>  =back
>  
> +=item B<bios_path_override="PATH">
> +
> +Override the path to the blob to be used as BIOS. The blob provided here MUST
> +be consistent with the B<bios=> which you have specified. You should not
> +normally need to specify this option.
> +
> +This options does not have any effect if using B<bios="rombios"> or
> +B<device_model_version="qemu-xen-traditional">.
> +
>  =item B<pae=BOOLEAN>
>  
>  Hide or expose the IA32 Physical Address Extensions. These extensions
> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> index 48a43ce..5cccdc8 100644
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -942,6 +942,14 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, const libxl_mac *src);
>  #define LIBXL_HAVE_CHECKPOINTED_STREAM 1
>  
>  /*
> + * LIBXL_HAVE_BUILDINFO_HVM_SYSTEM_FIRMWARE
> + *
> + * libxl_domain_build_info has u.hvm.system_firmware field which can be use
> + * to provide a different firmware blob (like SeaBIOS or OVMF).
> + */
> +#define LIBXL_HAVE_BUILDINFO_HVM_SYSTEM_FIRMWARE
> +
> +/*
>   * ERROR_REMUS_XXX error code only exists from Xen 4.5, Xen 4.6 and it
>   * is changed to ERROR_CHECKPOINT_XXX in Xen 4.7
>   */
> diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
> index ec29060..2a1793d 100644
> --- a/tools/libxl/libxl_dom.c
> +++ b/tools/libxl/libxl_dom.c
> @@ -862,6 +862,42 @@ err:
>      return ret;
>  }
>  
> +static int libxl__load_hvm_firmware_module(libxl__gc *gc,
> +                                           const char *filename,
> +                                           const char *what,
> +                                           struct xc_hvm_firmware_module *m)
> +{
> +    int datalen = 0;
> +    void *data = NULL;
> +    int r, rc;
> +
> +    LOG(DEBUG, "Loading %s: %s", what, filename);
> +    r = libxl_read_file_contents(CTX, filename, &data, &datalen);
> +    if (r) {
> +        /*
> +         * Print a message only on ENOENT, other errors are logged by the
> +         * function libxl_read_file_contents().
> +         */
> +        if (r == ENOENT)
> +            LOGEV(ERROR, r, "failed to read %s file", what);
> +        rc =  ERROR_FAIL;
> +        goto out;
> +    }
> +    libxl__ptr_add(gc, data);
> +    if (datalen) {
> +        /* Only accept non-empty files */
> +        m->data = data;
> +        m->length = datalen;
> +    } else {
> +        LOG(ERROR, "file %s for %s is empty", filename, what);
> +        rc = ERROR_INVAL;
> +        goto out;
> +    }
> +    rc = 0;
> +out:
> +    return rc;
> +}
> +
>  static int libxl__domain_firmware(libxl__gc *gc,
>                                    libxl_domain_build_info *info,
>                                    struct xc_dom_image *dom)
> @@ -871,6 +907,7 @@ static int libxl__domain_firmware(libxl__gc *gc,
>      int e, rc;
>      int datalen = 0;
>      void *data;
> +    const char *bios_filename = NULL;
>  
>      if (info->u.hvm.firmware)
>          firmware = info->u.hvm.firmware;
> @@ -914,6 +951,30 @@ static int libxl__domain_firmware(libxl__gc *gc,
>          goto out;
>      }
>  
> +    if (info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
> +        if (info->u.hvm.system_firmware) {
> +            bios_filename = info->u.hvm.system_firmware;
> +        } else {
> +            switch (info->u.hvm.bios) {
> +            case LIBXL_BIOS_TYPE_SEABIOS:
> +                bios_filename = libxl__seabios_path();
> +                break;
> +            case LIBXL_BIOS_TYPE_OVMF:
> +                bios_filename = libxl__ovmf_path();
> +                break;
> +            case LIBXL_BIOS_TYPE_ROMBIOS:
> +            default:
> +                abort();
> +            }
> +        }
> +    }
> +
> +    if (bios_filename) {
> +        rc = libxl__load_hvm_firmware_module(gc, bios_filename, "BIOS",
> +                                             &dom->system_firmware_module);
> +        if (rc) goto out;
> +    }
> +
>      if (info->u.hvm.smbios_firmware) {
>          data = NULL;
>          e = libxl_read_file_contents(ctx, info->u.hvm.smbios_firmware,
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 5347b69..991a1cc 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -2320,6 +2320,8 @@ _hidden const char *libxl__xen_config_dir_path(void);
>  _hidden const char *libxl__xen_script_dir_path(void);
>  _hidden const char *libxl__lock_dir_path(void);
>  _hidden const char *libxl__run_dir_path(void);
> +_hidden const char *libxl__seabios_path(void);
> +_hidden const char *libxl__ovmf_path(void);
>  
>  /*----- subprocess execution with timeout -----*/
>  
> diff --git a/tools/libxl/libxl_paths.c b/tools/libxl/libxl_paths.c
> index 9b7b0d5..6972b90 100644
> --- a/tools/libxl/libxl_paths.c
> +++ b/tools/libxl/libxl_paths.c
> @@ -35,6 +35,16 @@ const char *libxl__run_dir_path(void)
>      return XEN_RUN_DIR;
>  }
>  
> +const char *libxl__seabios_path(void)
> +{
> +    return SEABIOS_PATH;
> +}
> +
> +const char *libxl__ovmf_path(void)
> +{
> +    return OVMF_PATH;
> +}
> +
Hi, I got bellow errors when compiling on ARM.

libxl_paths.c: In function 'libxl__seabios_path':
libxl_paths.c:40:12: error: 'SEABIOS_PATH' undeclared (first use in this
function)
     return SEABIOS_PATH;
            ^
libxl_paths.c:40:12: note: each undeclared identifier is reported only
once for each function it appears in
libxl_paths.c: In function 'libxl__ovmf_path':
libxl_paths.c:45:12: error: 'OVMF_PATH' undeclared (first use in this
function)
     return OVMF_PATH;
            ^
libxl_paths.c: In function 'libxl__seabios_path':
libxl_paths.c:41:1: error: control reaches end of non-void function
[-Werror=return-type]
 }
 ^
libxl_paths.c: In function 'libxl__ovmf_path':
libxl_paths.c:46:1: error: control reaches end of non-void function
[-Werror=return-type]
 }
 ^
cc1: all warnings being treated as errors

Thanks,
Wei Liu Aug. 15, 2016, 9:09 a.m. UTC | #2
On Mon, Aug 15, 2016 at 05:04:20PM +0800, Shannon Zhao wrote:
[...]
> >  
> > +const char *libxl__seabios_path(void)
> > +{
> > +    return SEABIOS_PATH;
> > +}
> > +
> > +const char *libxl__ovmf_path(void)
> > +{
> > +    return OVMF_PATH;
> > +}
> > +
> Hi, I got bellow errors when compiling on ARM.
> 
> libxl_paths.c: In function 'libxl__seabios_path':
> libxl_paths.c:40:12: error: 'SEABIOS_PATH' undeclared (first use in this
> function)
>      return SEABIOS_PATH;
>             ^
> libxl_paths.c:40:12: note: each undeclared identifier is reported only
> once for each function it appears in
> libxl_paths.c: In function 'libxl__ovmf_path':
> libxl_paths.c:45:12: error: 'OVMF_PATH' undeclared (first use in this
> function)
>      return OVMF_PATH;
>             ^
> libxl_paths.c: In function 'libxl__seabios_path':
> libxl_paths.c:41:1: error: control reaches end of non-void function
> [-Werror=return-type]
>  }
>  ^
> libxl_paths.c: In function 'libxl__ovmf_path':
> libxl_paths.c:46:1: error: control reaches end of non-void function
> [-Werror=return-type]
>  }
>  ^
> cc1: all warnings being treated as errors
> 

Have you tried to run ./autogen.sh in xen.git top-level directory?

Wei.

> Thanks,
> -- 
> Shannon
>
Shannon Zhao Aug. 15, 2016, 9:14 a.m. UTC | #3
On 2016/8/15 17:09, Wei Liu wrote:
> On Mon, Aug 15, 2016 at 05:04:20PM +0800, Shannon Zhao wrote:
> [...]
>>> > >  
>>> > > +const char *libxl__seabios_path(void)
>>> > > +{
>>> > > +    return SEABIOS_PATH;
>>> > > +}
>>> > > +
>>> > > +const char *libxl__ovmf_path(void)
>>> > > +{
>>> > > +    return OVMF_PATH;
>>> > > +}
>>> > > +
>> > Hi, I got bellow errors when compiling on ARM.
>> > 
>> > libxl_paths.c: In function 'libxl__seabios_path':
>> > libxl_paths.c:40:12: error: 'SEABIOS_PATH' undeclared (first use in this
>> > function)
>> >      return SEABIOS_PATH;
>> >             ^
>> > libxl_paths.c:40:12: note: each undeclared identifier is reported only
>> > once for each function it appears in
>> > libxl_paths.c: In function 'libxl__ovmf_path':
>> > libxl_paths.c:45:12: error: 'OVMF_PATH' undeclared (first use in this
>> > function)
>> >      return OVMF_PATH;
>> >             ^
>> > libxl_paths.c: In function 'libxl__seabios_path':
>> > libxl_paths.c:41:1: error: control reaches end of non-void function
>> > [-Werror=return-type]
>> >  }
>> >  ^
>> > libxl_paths.c: In function 'libxl__ovmf_path':
>> > libxl_paths.c:46:1: error: control reaches end of non-void function
>> > [-Werror=return-type]
>> >  }
>> >  ^
>> > cc1: all warnings being treated as errors
>> > 
> Have you tried to run ./autogen.sh in xen.git top-level directory?
Eh, I only ran ./configure and make dist-tools as before. ./autogen.sh
makes it work.

Thanks,
Wei Liu Aug. 15, 2016, 9:17 a.m. UTC | #4
On Mon, Aug 15, 2016 at 05:14:43PM +0800, Shannon Zhao wrote:
> 
> 
> On 2016/8/15 17:09, Wei Liu wrote:
> > On Mon, Aug 15, 2016 at 05:04:20PM +0800, Shannon Zhao wrote:
> > [...]
> >>> > >  
> >>> > > +const char *libxl__seabios_path(void)
> >>> > > +{
> >>> > > +    return SEABIOS_PATH;
> >>> > > +}
> >>> > > +
> >>> > > +const char *libxl__ovmf_path(void)
> >>> > > +{
> >>> > > +    return OVMF_PATH;
> >>> > > +}
> >>> > > +
> >> > Hi, I got bellow errors when compiling on ARM.
> >> > 
> >> > libxl_paths.c: In function 'libxl__seabios_path':
> >> > libxl_paths.c:40:12: error: 'SEABIOS_PATH' undeclared (first use in this
> >> > function)
> >> >      return SEABIOS_PATH;
> >> >             ^
> >> > libxl_paths.c:40:12: note: each undeclared identifier is reported only
> >> > once for each function it appears in
> >> > libxl_paths.c: In function 'libxl__ovmf_path':
> >> > libxl_paths.c:45:12: error: 'OVMF_PATH' undeclared (first use in this
> >> > function)
> >> >      return OVMF_PATH;
> >> >             ^
> >> > libxl_paths.c: In function 'libxl__seabios_path':
> >> > libxl_paths.c:41:1: error: control reaches end of non-void function
> >> > [-Werror=return-type]
> >> >  }
> >> >  ^
> >> > libxl_paths.c: In function 'libxl__ovmf_path':
> >> > libxl_paths.c:46:1: error: control reaches end of non-void function
> >> > [-Werror=return-type]
> >> >  }
> >> >  ^
> >> > cc1: all warnings being treated as errors
> >> > 
> > Have you tried to run ./autogen.sh in xen.git top-level directory?
> Eh, I only ran ./configure and make dist-tools as before. ./autogen.sh
> makes it work.
> 

Good to hear that solved your problem.

Anthony didn't commit the changes to configure that's why you saw those
errors.

Wei.

> Thanks,
> -- 
> Shannon
>
diff mbox

Patch

diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
index 3bb27d0..a685b83 100644
--- a/docs/man/xl.cfg.pod.5.in
+++ b/docs/man/xl.cfg.pod.5.in
@@ -1212,6 +1212,15 @@  Requires device_model_version=qemu-xen.
 
 =back
 
+=item B<bios_path_override="PATH">
+
+Override the path to the blob to be used as BIOS. The blob provided here MUST
+be consistent with the B<bios=> which you have specified. You should not
+normally need to specify this option.
+
+This options does not have any effect if using B<bios="rombios"> or
+B<device_model_version="qemu-xen-traditional">.
+
 =item B<pae=BOOLEAN>
 
 Hide or expose the IA32 Physical Address Extensions. These extensions
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 48a43ce..5cccdc8 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -942,6 +942,14 @@  void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, const libxl_mac *src);
 #define LIBXL_HAVE_CHECKPOINTED_STREAM 1
 
 /*
+ * LIBXL_HAVE_BUILDINFO_HVM_SYSTEM_FIRMWARE
+ *
+ * libxl_domain_build_info has u.hvm.system_firmware field which can be use
+ * to provide a different firmware blob (like SeaBIOS or OVMF).
+ */
+#define LIBXL_HAVE_BUILDINFO_HVM_SYSTEM_FIRMWARE
+
+/*
  * ERROR_REMUS_XXX error code only exists from Xen 4.5, Xen 4.6 and it
  * is changed to ERROR_CHECKPOINT_XXX in Xen 4.7
  */
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index ec29060..2a1793d 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -862,6 +862,42 @@  err:
     return ret;
 }
 
+static int libxl__load_hvm_firmware_module(libxl__gc *gc,
+                                           const char *filename,
+                                           const char *what,
+                                           struct xc_hvm_firmware_module *m)
+{
+    int datalen = 0;
+    void *data = NULL;
+    int r, rc;
+
+    LOG(DEBUG, "Loading %s: %s", what, filename);
+    r = libxl_read_file_contents(CTX, filename, &data, &datalen);
+    if (r) {
+        /*
+         * Print a message only on ENOENT, other errors are logged by the
+         * function libxl_read_file_contents().
+         */
+        if (r == ENOENT)
+            LOGEV(ERROR, r, "failed to read %s file", what);
+        rc =  ERROR_FAIL;
+        goto out;
+    }
+    libxl__ptr_add(gc, data);
+    if (datalen) {
+        /* Only accept non-empty files */
+        m->data = data;
+        m->length = datalen;
+    } else {
+        LOG(ERROR, "file %s for %s is empty", filename, what);
+        rc = ERROR_INVAL;
+        goto out;
+    }
+    rc = 0;
+out:
+    return rc;
+}
+
 static int libxl__domain_firmware(libxl__gc *gc,
                                   libxl_domain_build_info *info,
                                   struct xc_dom_image *dom)
@@ -871,6 +907,7 @@  static int libxl__domain_firmware(libxl__gc *gc,
     int e, rc;
     int datalen = 0;
     void *data;
+    const char *bios_filename = NULL;
 
     if (info->u.hvm.firmware)
         firmware = info->u.hvm.firmware;
@@ -914,6 +951,30 @@  static int libxl__domain_firmware(libxl__gc *gc,
         goto out;
     }
 
+    if (info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
+        if (info->u.hvm.system_firmware) {
+            bios_filename = info->u.hvm.system_firmware;
+        } else {
+            switch (info->u.hvm.bios) {
+            case LIBXL_BIOS_TYPE_SEABIOS:
+                bios_filename = libxl__seabios_path();
+                break;
+            case LIBXL_BIOS_TYPE_OVMF:
+                bios_filename = libxl__ovmf_path();
+                break;
+            case LIBXL_BIOS_TYPE_ROMBIOS:
+            default:
+                abort();
+            }
+        }
+    }
+
+    if (bios_filename) {
+        rc = libxl__load_hvm_firmware_module(gc, bios_filename, "BIOS",
+                                             &dom->system_firmware_module);
+        if (rc) goto out;
+    }
+
     if (info->u.hvm.smbios_firmware) {
         data = NULL;
         e = libxl_read_file_contents(ctx, info->u.hvm.smbios_firmware,
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 5347b69..991a1cc 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2320,6 +2320,8 @@  _hidden const char *libxl__xen_config_dir_path(void);
 _hidden const char *libxl__xen_script_dir_path(void);
 _hidden const char *libxl__lock_dir_path(void);
 _hidden const char *libxl__run_dir_path(void);
+_hidden const char *libxl__seabios_path(void);
+_hidden const char *libxl__ovmf_path(void);
 
 /*----- subprocess execution with timeout -----*/
 
diff --git a/tools/libxl/libxl_paths.c b/tools/libxl/libxl_paths.c
index 9b7b0d5..6972b90 100644
--- a/tools/libxl/libxl_paths.c
+++ b/tools/libxl/libxl_paths.c
@@ -35,6 +35,16 @@  const char *libxl__run_dir_path(void)
     return XEN_RUN_DIR;
 }
 
+const char *libxl__seabios_path(void)
+{
+    return SEABIOS_PATH;
+}
+
+const char *libxl__ovmf_path(void)
+{
+    return OVMF_PATH;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index ef614be..98bfc3a 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -513,6 +513,7 @@  libxl_domain_build_info = Struct("domain_build_info",[
                                        ("timer_mode",       libxl_timer_mode),
                                        ("nested_hvm",       libxl_defbool),
                                        ("altp2m",           libxl_defbool),
+                                       ("system_firmware",  string),
                                        ("smbios_firmware",  string),
                                        ("acpi_firmware",    string),
                                        ("hdtype",           libxl_hdtype),
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index d1fcfa4..1d06598 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -1562,12 +1562,17 @@  static void parse_config_data(const char *config_source,
 
         xlu_cfg_replace_string (config, "firmware_override",
                                 &b_info->u.hvm.firmware, 0);
-        if (!xlu_cfg_get_string(config, "bios", &buf, 0) &&
-            libxl_bios_type_from_string(buf, &b_info->u.hvm.bios)) {
+        xlu_cfg_replace_string (config, "bios_path_override",
+                                &b_info->u.hvm.system_firmware, 0);
+        if (!xlu_cfg_get_string(config, "bios", &buf, 0)) {
+            if (libxl_bios_type_from_string(buf, &b_info->u.hvm.bios)) {
                 fprintf(stderr, "ERROR: invalid value \"%s\" for \"bios\"\n",
                     buf);
                 exit (1);
-        }
+            }
+        } else if (b_info->u.hvm.system_firmware)
+            fprintf(stderr, "WARNING: "
+                    "bios_path_override given without specific bios name\n");
 
         xlu_cfg_get_defbool(config, "pae", &b_info->u.hvm.pae, 0);
         xlu_cfg_get_defbool(config, "apic", &b_info->u.hvm.apic, 0);