[PATCH v2 1/4] xl: Add support for ignore_msrs option

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

This option allows guest administrator specify what should happen when
guest accesses an MSR which is not explicitly emulated by the hypervisor.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 docs/man/xl.cfg.5.pod.in         | 20 +++++++++++++++++++-
 tools/libs/light/libxl_types.idl |  7 +++++++
 tools/xl/xl_parse.c              |  7 +++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index c8e017f950de..96ce97c42cab 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -2044,7 +2044,25 @@ Do not provide a VM generation ID.
 See also "Virtual Machine Generation ID" by Microsoft:
 
L<https://docs.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-machine-generation-identifier>
 
-=back 
+=over
+
+=item B<ignore_msrs="STRING">
+
+Determine hypervisor behavior on accesses to MSRs that are not emulated by the 
hypervisor.
+
+=over 4
+
+=item B<never>
+
+Issue a warning to the log and #GP to the guest. This is default.
+
+=item B<silent>
+
+MSR reads return 0, MSR writes are ignored. No warnings to the log.
+
+=item B<verbose>
+
+Similar to B<silent> but a warning is written.
 
 =head3 Guest Virtual Time Controls
 
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 05324736b744..7b5fef771ee8 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -477,6 +477,12 @@ libxl_tee_type = Enumeration("tee_type", [
     (1, "optee")
     ], init_val = "LIBXL_TEE_TYPE_NONE")
 
+libxl_ignore_msrs = Enumeration("ignore_msrs", [
+    (0, "never"),
+    (1, "silent"),
+    (2, "verbose"),
+    ], init_val = "LIBXL_IGNORE_MSRS_NEVER")
+
 libxl_rdm_reserve = Struct("rdm_reserve", [
     ("strategy",    libxl_rdm_reserve_strategy),
     ("policy",      libxl_rdm_reserve_policy),
@@ -559,6 +565,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
     ("apic",             libxl_defbool),
     ("dm_restrict",      libxl_defbool),
     ("tee",              libxl_tee_type),
+    ("ignore_msrs",      libxl_ignore_msrs),
     ("u", KeyedUnion(None, libxl_domain_type, "type",
                 [("hvm", Struct(None, [("firmware",         string),
                                        ("bios",             libxl_bios_type),
diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 4ebf39620ae7..942086c3f41d 100644
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -2732,6 +2732,13 @@ skip_usbdev:
         }
     }
 
+    if (!xlu_cfg_get_string(config, "ignore_msrs", &buf, 0)) {
+        if (libxl_ignore_msrs_from_string(buf, &b_info->ignore_msrs)) {
+           fprintf(stderr, "ERROR: invalid value \"%s\" for 
\"ignore_msrs\"\n", buf);
+           exit(1);
+        }
+    }
+
     parse_vkb_list(config, d_config);
 
     xlu_cfg_get_defbool(config, "xend_suspend_evtchn_compat",
-- 
1.8.3.1