tools/[lib]xl: Add vmtrace_buf_size parameter

Allow to specify the size of per-vCPU trace buffer upon
domain creation. This is zero by default (meaning: not enabled).

Signed-off-by: Michał Leszczyński <michal.leszczynski@cert.pl>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

docs/man/xl.cfg.5.pod.in

@@ -681,6 +681,15 @@ Windows).
 
 If this option is not specified then it will default to B<false>.
 
+=item B<vmtrace_buf_kb=KBYTES>
+
+Specifies the size of vmtrace buffer that would be allocated for each
+vCPU belonging to this domain.  Disabled (i.e.  B<vmtrace_buf_kb=0>) by
+default.
+
+B<NOTE>: Acceptable values are platform specific.  For Intel Processor
+Trace, this value must be a power of 2 between 4k and 16M.
+
 =back
 
 =head2 Devices

tools/golang/xenlight/helpers.gen.go

@@ -1114,6 +1114,7 @@ return fmt.Errorf("invalid union key '%v'", x.Type)}
 x.ArchArm.GicVersion = GicVersion(xc.arch_arm.gic_version)
 x.ArchArm.Vuart = VuartType(xc.arch_arm.vuart)
 x.Altp2M = Altp2MMode(xc.altp2m)
+x.VmtraceBufKb = int(xc.vmtrace_buf_kb)
 
  return nil}
 
@@ -1589,6 +1590,7 @@ return fmt.Errorf("invalid union key '%v'", x.Type)}
 xc.arch_arm.gic_version = C.libxl_gic_version(x.ArchArm.GicVersion)
 xc.arch_arm.vuart = C.libxl_vuart_type(x.ArchArm.Vuart)
 xc.altp2m = C.libxl_altp2m_mode(x.Altp2M)
+xc.vmtrace_buf_kb = C.int(x.VmtraceBufKb)
 
  return nil
  }

tools/golang/xenlight/types.gen.go

@@ -514,6 +514,7 @@ GicVersion GicVersion
 Vuart VuartType
 }
 Altp2M Altp2MMode
+VmtraceBufKb int
 }
 
 type domainBuildInfoTypeUnion interface {

tools/include/libxl.h

@@ -488,6 +488,13 @@
  */
 #define LIBXL_HAVE_PHYSINFO_CAP_VMTRACE 1
 
+/*
+ * LIBXL_HAVE_VMTRACE_BUF_KB indicates that libxl_domain_create_info has a
+ * vmtrace_buf_kb parameter, which allows to enable pre-allocation of
+ * processor tracing buffers of given size.
+ */
+#define LIBXL_HAVE_VMTRACE_BUF_KB 1
+
 /*
  * libxl ABI compatibility
  *

tools/libs/light/libxl_create.c

@@ -607,6 +607,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
             .max_evtchn_port = b_info->event_channels,
             .max_grant_frames = b_info->max_grant_frames,
             .max_maptrack_frames = b_info->max_maptrack_frames,
+            .vmtrace_size = ROUNDUP(b_info->vmtrace_buf_kb << 10, XC_PAGE_SHIFT),
         };
 
         if (info->type != LIBXL_DOMAIN_TYPE_PV) {

tools/libs/light/libxl_types.idl

@@ -648,6 +648,10 @@ libxl_domain_build_info = Struct("domain_build_info",[
     # supported by x86 HVM and ARM support is planned.
     ("altp2m", libxl_altp2m_mode),
 
+    # Size of preallocated vmtrace trace buffers (in KBYTES).
+    # Use zero value to disable this feature.
+    ("vmtrace_buf_kb", integer),
+
     ], dir=DIR_IN,
        copy_deprecated_fn="libxl__domain_build_info_copy_deprecated",
 )

tools/xl/xl_parse.c

@@ -1863,6 +1863,10 @@ void parse_config_data(const char *config_source,
         }
     }
 
+    if (!xlu_cfg_get_long(config, "vmtrace_buf_kb", &l, 1) && l) {
+        b_info->vmtrace_buf_kb = l;
+    }
+
     if (!xlu_cfg_get_list(config, "ioports", &ioports, &num_ioports, 0)) {
         b_info->num_ioports = num_ioports;
         b_info->ioports = calloc(num_ioports, sizeof(*b_info->ioports));