[PATCH v3 4/5] tools, libxl: parse optional start gfn from the iomem config option

[Arianna Avanzini <avanzini.arianna@gmail.com>]

Currently the "iomem" domU config option allows to specify a machine
address range to be mapped to the domU. However, there is no way to
specify the guest address range used for the mapping. This commit
extends the iomem config option code to parse an additional, optional
parameter: this parameter, if given, specifies the start guest address
used for the mapping; if no start guest address is given, a 1:1 mapping
is performed as default.

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Paolo Valente <paolo.valente@unimore.it>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Julien Grall <julien.grall@citrix.com>
Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Eric Trudeau <etrudeau@broadcom.com>
Cc: Viktor Kleinik <viktor.kleinik@globallogic.com>
---
 docs/man/xl.cfg.pod.5       |  7 ++++---
 tools/libxl/libxl_types.idl |  1 +
 tools/libxl/xl_cmdimpl.c    | 22 +++++++++++++++-------
 3 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index a6663b9..d9684f2 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -602,12 +602,13 @@ is given in hexadecimal and may either a span e.g. C<2f8-2ff>
 It is recommended to use this option only for trusted VMs under
 administrator control.
 
-=item B<iomem=[ "IOMEM_START,NUM_PAGES", "IOMEM_START,NUM_PAGES", ... ]>
+=item B<iomem=[ "IOMEM_START,NUM_PAGES[@GFN]", "IOMEM_START,NUM_PAGES[@GFN]", ... ]>
 
 Allow guest to access specific hardware I/O memory pages. B<IOMEM_START>
 is a physical page number. B<NUM_PAGES> is the number
-of pages beginning with B<START_PAGE> to allow access. Both values
-must be given in hexadecimal.
+of pages beginning with B<START_PAGE> to allow access. B<GFN> specifies
+the guest frame number where the mapping will start in the domU's
+address space. All of these values must be given in hexadecimal.
 
 It is recommended to use this option only for trusted VMs under
 administrator control.
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 612645c..f0bdb09 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -172,6 +172,7 @@ libxl_ioport_range = Struct("ioport_range", [
 libxl_iomem_range = Struct("iomem_range", [
     ("start", uint64),
     ("number", uint64),
+    ("gfn", uint64),
     ])
 
 libxl_vga_interface_info = Struct("vga_interface_info", [
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 6b1ebfa..cf8d71f 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -1220,13 +1220,21 @@ static void parse_config_data(const char *config_source,
                         "xl: Unable to get element %d in iomem list\n", i);
                 exit(1);
             }
-            if(sscanf(buf, "%" SCNx64",%" SCNx64,
-                     &b_info->iomem[i].start,
-                     &b_info->iomem[i].number)
-                  != 2) {
-               fprintf(stderr,
-                       "xl: Invalid argument parsing iomem: %s\n", buf);
-               exit(1);
+            if(sscanf(buf, "%" SCNx64",%" SCNx64"@%" SCNx64,
+                      &b_info->iomem[i].start,
+                      &b_info->iomem[i].number,
+                      &b_info->iomem[i].gfn)
+                  != 3) {
+                if(sscanf(buf, "%" SCNx64",%" SCNx64,
+                          &b_info->iomem[i].start,
+                          &b_info->iomem[i].number)
+                      != 2) {
+                    fprintf(stderr,
+                            "xl: Invalid argument parsing iomem: %s\n", buf);
+                    exit(1);
+                } else
+                    /* default to 1:1 mapping */
+                    b_info->iomem[i].gfn = b_info->iomem[i].start;
             }
         }
     }
-- 
1.9.0