[PATCH v4 3/5] tools/arm: Add the trap_unmapped_accesses xl config option

["Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>]

From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
---
 docs/man/xl.cfg.5.pod.in         | 9 +++++++++
 tools/include/libxl.h            | 7 +++++++
 tools/libs/light/libxl_arm.c     | 6 +++---
 tools/libs/light/libxl_create.c  | 3 +++
 tools/libs/light/libxl_types.idl | 1 +
 tools/libs/light/libxl_x86.c     | 6 ++++++
 tools/xl/xl_parse.c              | 3 +++
 7 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index c388899306..075e89e6d2 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -3056,6 +3056,15 @@ will be used for the domain. Otherwise, the value 
specified by the `nr_spis`
 parameter will be used. The number of SPIs should match the highest interrupt
 ID that will be assigned to the domain.
 
+=item B<trap_unmapped_accesses=BOOLEAN>
+
+An Optional boolean parameter that configures handling of accesses to unmapped
+address ranges. If enabled, guest accesses will trap. If disabled, guest
+accesses will read all bits as ones, e.g 0xFFFFFFFF for a 32bit access and
+writes will be ignored.
+
+This option is only implemented for Arm where the default is enabled.
+
 =back
 
 =head3 x86
diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index b7ad7735ca..24c81cf145 100644
--- a/tools/include/libxl.h
+++ b/tools/include/libxl.h
@@ -549,6 +549,13 @@
  */
 #define LIBXL_HAVE_VPMU 1
 
+/*
+ * LIBXL_HAVE_TRAP_UNMAPPED_ACCESSES indicates that libxl_domain_build_info
+ * has a trap_unmapped_accesses parameter, which allows the control of how
+ * accesses to unmapped adresses behave.
+ */
+#define LIBXL_HAVE_TRAP_UNMAPPED_ACCESSES 1
+
 /*
  * LIBXL_HAVE_PHYSINFO_CAP_GNTTAB indicates that libxl_physinfo has a
  * cap_gnttab_v1/2 fields, which indicates the available grant table ABIs.
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 9530996e72..afc62a5299 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -233,9 +233,6 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
         config->arch.sve_vl = d_config->b_info.arch_arm.sve_vl / 128U;
     }
 
-    /* Trap accesses to unmapped areas. */
-    config->flags |= XEN_DOMCTL_CDF_trap_unmapped_accesses;
-
     return 0;
 }
 
@@ -1714,6 +1711,9 @@ int libxl__arch_domain_build_info_setdefault(libxl__gc 
*gc,
     /* ACPI is disabled by default */
     libxl_defbool_setdefault(&b_info->acpi, false);
 
+    /* Trapping of unmapped accesses enabled by default.  */
+    libxl_defbool_setdefault(&b_info->trap_unmapped_accesses, true);
+
     /* Sanitise SVE parameter */
     if (b_info->arch_arm.sve_vl) {
         unsigned int max_sve_vl =
diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
index 8bc768b515..625ce5b040 100644
--- a/tools/libs/light/libxl_create.c
+++ b/tools/libs/light/libxl_create.c
@@ -605,6 +605,9 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config 
*d_config,
         if (libxl_defbool_val(b_info->vpmu))
             create.flags |= XEN_DOMCTL_CDF_vpmu;
 
+        if (libxl_defbool_val(b_info->trap_unmapped_accesses))
+            create.flags |= XEN_DOMCTL_CDF_trap_unmapped_accesses;
+
         assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
         LOG(DETAIL, "passthrough: %s",
             libxl_passthrough_to_string(info->passthrough));
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 1985153830..57ae16ae78 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -736,6 +736,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
     ("vmtrace_buf_kb", integer),
 
     ("vpmu", libxl_defbool),
+    ("trap_unmapped_accesses", libxl_defbool),
 
     ], dir=DIR_IN,
        copy_deprecated_fn="libxl__domain_build_info_copy_deprecated",
diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c
index 867addfcab..60d4e8661c 100644
--- a/tools/libs/light/libxl_x86.c
+++ b/tools/libs/light/libxl_x86.c
@@ -26,6 +26,11 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
     if (libxl_defbool_val(d_config->b_info.arch_x86.msr_relaxed))
         config->arch.misc_flags |= XEN_X86_MSR_RELAXED;
 
+    if (libxl_defbool_val(d_config->b_info.trap_unmapped_accesses)) {
+            LOG(ERROR, "trap_unmapped_accesses is not supported on x86\n");
+            return ERROR_FAIL;
+    }
+
     return 0;
 }
 
@@ -813,6 +818,7 @@ int libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
 {
     libxl_defbool_setdefault(&b_info->acpi, true);
     libxl_defbool_setdefault(&b_info->arch_x86.msr_relaxed, false);
+    libxl_defbool_setdefault(&b_info->trap_unmapped_accesses, false);
 
     if (b_info->type == LIBXL_DOMAIN_TYPE_HVM) {
         /*
diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 219e924779..98b3612d0f 100644
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -2972,6 +2972,9 @@ skip_usbdev:
     if (!xlu_cfg_get_long (config, "nr_spis", &l, 0))
         b_info->arch_arm.nr_spis = l;
 
+    xlu_cfg_get_defbool(config, "trap_unmapped_accesses",
+                        &b_info->trap_unmapped_accesses, 0);
+
     parse_vkb_list(config, d_config);
 
     d_config->virtios = NULL;
-- 
2.43.0