[PATCH v8 09/12] xen: add runtime parameter access support to hypfs

[Juergen Gross <jgross@xxxxxxxx>]

Add support to read and modify values of hypervisor runtime parameters
via the hypervisor file system.

As runtime parameters can be modified via a sysctl, too, this path has
to take the hypfs rw_lock as writer.

For custom runtime parameters the connection between the parameter
value and the file system is done via an init function which will set
the initial value (if needed) and the leaf properties.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- complete rework
- support custom parameters, too
- support parameter writing

V6:
- rewording in docs/misc/hypfs-paths.pandoc (Jan Beulich)
- use memchr() (Jan Beulich)
- use strlcat() (Jan Beulich)
- rework to use a custom parameter init function instead of a reference
  to a content variable, allowing to drop default strings
- style correction (Jan Beulich)
- dropping param_append_str() in favor of a custom function at its only
  use site

V7:
- fine tune some parameter initializations (Jan Beulich)
- call custom_runtime_set_var() after updating the value
- modify alignment in Arm linker script to 4 (Jan Beulich)

V8:
- modify alignment in Arm linker script to 8 (Julien Grall)
- fix ept runtime parameter reporting (Jan Beulich)
- rebase to support CONFIG_HYPFS

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 docs/misc/hypfs-paths.pandoc |   9 +++
 xen/arch/arm/xen.lds.S       |   7 ++
 xen/arch/x86/hvm/vmx/vmcs.c  |  29 +++++++-
 xen/arch/x86/pv/domain.c     |  24 ++++++-
 xen/arch/x86/xen.lds.S       |   7 ++
 xen/common/grant_table.c     |  62 ++++++++++++++----
 xen/common/hypfs.c           |  41 ++++++++++++
 xen/common/kernel.c          |  27 +++++++-
 xen/drivers/char/console.c   |  77 ++++++++++++++++++++--
 xen/include/xen/hypfs.h      |   7 ++
 xen/include/xen/param.h      | 124 ++++++++++++++++++++++++++++++++++-
 11 files changed, 390 insertions(+), 24 deletions(-)

diff --git a/docs/misc/hypfs-paths.pandoc b/docs/misc/hypfs-paths.pandoc
index 9a76bc383b..a111c6f25c 100644
--- a/docs/misc/hypfs-paths.pandoc
+++ b/docs/misc/hypfs-paths.pandoc
@@ -154,3 +154,12 @@ The major version of Xen.
 #### /buildinfo/version/minor = INTEGER
 
 The minor version of Xen.
+
+#### /params/
+
+A directory of runtime parameters.
+
+#### /params/*
+
+The individual parameters. The description of the different parameters can be
+found in `docs/misc/xen-command-line.pandoc`.
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index a497f6a48d..0a6efe96cf 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -89,6 +89,13 @@ SECTIONS
        __start_schedulers_array = .;
        *(.data.schedulers)
        __end_schedulers_array = .;
+
+#ifdef CONFIG_HYPFS
+       . = ALIGN(8);
+       __paramhypfs_start = .;
+       *(.data.paramhypfs)
+       __paramhypfs_end = .;
+#endif
        *(.data.rel)
        *(.data.rel.*)
        CONSTRUCTORS
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 221af9737a..1746385d13 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -71,6 +71,27 @@ static bool __read_mostly opt_ept_pml = true;
 static s8 __read_mostly opt_ept_ad = -1;
 int8_t __read_mostly opt_ept_exec_sp = -1;
 
+#ifdef CONFIG_HYPFS
+static char opt_ept_setting[10];
+
+static void update_ept_param(void)
+{
+    if ( opt_ept_exec_sp >= 0 )
+        snprintf(opt_ept_setting, sizeof(opt_ept_setting), "exec-sp=%d",
+                 opt_ept_exec_sp);
+}
+
+static void __init init_ept_param(struct param_hypfs *par)
+{
+    update_ept_param();
+    custom_runtime_set_var(par, opt_ept_setting);
+}
+#else
+static void update_ept_param(void)
+{
+}
+#endif
+
 static int __init parse_ept_param(const char *s)
 {
     const char *ss;
@@ -97,6 +118,9 @@ static int __init parse_ept_param(const char *s)
 }
 custom_param("ept", parse_ept_param);
 
+static int parse_ept_param_runtime(const char *s);
+custom_runtime_only_param("ept", parse_ept_param_runtime, init_ept_param);
+
 static int parse_ept_param_runtime(const char *s)
 {
     struct domain *d;
@@ -115,6 +139,10 @@ static int parse_ept_param_runtime(const char *s)
 
     opt_ept_exec_sp = val;
 
+    update_ept_param();
+    custom_runtime_set_var(param_2_parfs(parse_ept_param_runtime),
+                           opt_ept_setting);
+
     rcu_read_lock(&domlist_read_lock);
     for_each_domain ( d )
     {
@@ -144,7 +172,6 @@ static int parse_ept_param_runtime(const char *s)
 
     return 0;
 }
-custom_runtime_only_param("ept", parse_ept_param_runtime);
 
 /* Dynamic (run-time adjusted) execution control flags. */
 u32 vmx_pin_based_exec_control __read_mostly;
diff --git a/xen/arch/x86/pv/domain.c b/xen/arch/x86/pv/domain.c
index 0a4a5bd001..6bfce9a76a 100644
--- a/xen/arch/x86/pv/domain.c
+++ b/xen/arch/x86/pv/domain.c
@@ -52,9 +52,27 @@ static __read_mostly enum {
     PCID_OFF,
     PCID_ALL,
     PCID_XPTI,
-    PCID_NOXPTI
+    PCID_NOXPTI,
+    PCID_END
 } opt_pcid = PCID_XPTI;
 
+#ifdef CONFIG_HYPFS
+static const char opt_pcid_2_string[PCID_END][7] = {
+    [PCID_OFF] = "off",
+    [PCID_ALL] = "on",
+    [PCID_XPTI] = "xpti",
+    [PCID_NOXPTI] = "noxpti"
+};
+
+static void __init opt_pcid_init(struct param_hypfs *par)
+{
+    custom_runtime_set_var(par, opt_pcid_2_string[opt_pcid]);
+}
+#endif
+
+static int parse_pcid(const char *s);
+custom_runtime_param("pcid", parse_pcid, opt_pcid_init);
+
 static int parse_pcid(const char *s)
 {
     int rc = 0;
@@ -87,9 +105,11 @@ static int parse_pcid(const char *s)
         break;
     }
 
+    custom_runtime_set_var(param_2_parfs(parse_pcid),
+                           opt_pcid_2_string[opt_pcid]);
+
     return rc;
 }
-custom_runtime_param("pcid", parse_pcid);
 
 static void noreturn continue_nonidle_domain(struct vcpu *v)
 {
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 0e3a733cab..3ed020e26b 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -279,6 +279,13 @@ SECTIONS
        __start_schedulers_array = .;
        *(.data.schedulers)
        __end_schedulers_array = .;
+
+#ifdef CONFIG_HYPFS
+       . = ALIGN(8);
+       __paramhypfs_start = .;
+       *(.data.paramhypfs)
+       __paramhypfs_end = .;
+#endif
   } :text
 
   DECL_SECTION(.data) {
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 5ef7ff940d..a9eeee8ff9 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -85,8 +85,43 @@ struct grant_table {
     struct grant_table_arch arch;
 };
 
-static int parse_gnttab_limit(const char *param, const char *arg,
-                              unsigned int *valp)
+unsigned int __read_mostly opt_max_grant_frames = 64;
+static unsigned int __read_mostly opt_max_maptrack_frames = 1024;
+
+#ifdef CONFIG_HYPFS
+#define GRANT_CUSTOM_VAL_SZ  12
+static char __read_mostly opt_max_grant_frames_val[GRANT_CUSTOM_VAL_SZ];
+static char __read_mostly opt_max_maptrack_frames_val[GRANT_CUSTOM_VAL_SZ];
+
+static void update_gnttab_par(struct param_hypfs *par, unsigned int val,
+                              char *parval)
+{
+    snprintf(parval, GRANT_CUSTOM_VAL_SZ, "%u", val);
+    custom_runtime_set_var_sz(par, parval, GRANT_CUSTOM_VAL_SZ);
+}
+
+static void __init gnttab_max_frames_init(struct param_hypfs *par)
+{
+    update_gnttab_par(par, opt_max_grant_frames, opt_max_grant_frames_val);
+}
+
+static void __init max_maptrack_frames_init(struct param_hypfs *par)
+{
+    update_gnttab_par(par, opt_max_maptrack_frames,
+                      opt_max_maptrack_frames_val);
+}
+#else
+#define opt_max_grant_frames_val    NULL
+#define opt_max_maptrack_frames_val NULL
+
+static void update_gnttab_par(struct param_hypfs *par, unsigned int val,
+                              char *parval)
+{
+}
+#endif
+
+static int parse_gnttab_limit(struct param_hypfs *par, const char *arg,
+                              unsigned int *valp, char *parval)
 {
     const char *e;
     unsigned long val;
@@ -99,28 +134,33 @@ static int parse_gnttab_limit(const char *param, const 
char *arg,
         return -ERANGE;
 
     *valp = val;
+    update_gnttab_par(par, val, parval);
 
     return 0;
 }
 
-unsigned int __read_mostly opt_max_grant_frames = 64;
+static int parse_gnttab_max_frames(const char *arg);
+custom_runtime_param("gnttab_max_frames", parse_gnttab_max_frames,
+                     gnttab_max_frames_init);
 
 static int parse_gnttab_max_frames(const char *arg)
 {
-    return parse_gnttab_limit("gnttab_max_frames", arg,
-                              &opt_max_grant_frames);
+    return parse_gnttab_limit(param_2_parfs(parse_gnttab_max_frames),
+                              arg, &opt_max_grant_frames,
+                              opt_max_grant_frames_val);
 }
-custom_runtime_param("gnttab_max_frames", parse_gnttab_max_frames);
 
-static unsigned int __read_mostly opt_max_maptrack_frames = 1024;
+static int parse_gnttab_max_maptrack_frames(const char *arg);
+custom_runtime_param("gnttab_max_maptrack_frames",
+                     parse_gnttab_max_maptrack_frames,
+                     max_maptrack_frames_init);
 
 static int parse_gnttab_max_maptrack_frames(const char *arg)
 {
-    return parse_gnttab_limit("gnttab_max_maptrack_frames", arg,
-                              &opt_max_maptrack_frames);
+    return parse_gnttab_limit(param_2_parfs(parse_gnttab_max_maptrack_frames),
+                              arg, &opt_max_maptrack_frames,
+                              opt_max_maptrack_frames_val);
 }
-custom_runtime_param("gnttab_max_maptrack_frames",
-                     parse_gnttab_max_maptrack_frames);
 
 #ifndef GNTTAB_MAX_VERSION
 #define GNTTAB_MAX_VERSION 2
diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
index a873d507d1..e4de0a9eef 100644
--- a/xen/common/hypfs.c
+++ b/xen/common/hypfs.c
@@ -10,6 +10,7 @@
 #include <xen/hypercall.h>
 #include <xen/hypfs.h>
 #include <xen/lib.h>
+#include <xen/param.h>
 #include <xen/rwlock.h>
 #include <public/hypfs.h>
 
@@ -281,6 +282,36 @@ int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
     return 0;
 }
 
+int hypfs_write_custom(struct hypfs_entry_leaf *leaf,
+                       XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
+{
+    struct param_hypfs *p;
+    char *buf;
+    int ret;
+
+    buf = xzalloc_array(char, ulen);
+    if ( !buf )
+        return -ENOMEM;
+
+    ret = -EFAULT;
+    if ( copy_from_guest(buf, uaddr, ulen) )
+        goto out;
+
+    ret = -EDOM;
+    if ( memchr(buf, 0, ulen) != (buf + ulen - 1) )
+        goto out;
+
+    p = container_of(leaf, struct param_hypfs, hypfs);
+    ret = p->param->par.func(buf);
+
+    if ( !ret )
+        leaf->e.size = ulen;
+
+ out:
+    xfree(buf);
+    return ret;
+}
+
 static int hypfs_write(struct hypfs_entry *entry,
                        XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
 {
@@ -352,3 +383,13 @@ long do_hypfs_op(unsigned int cmd,
 
     return ret;
 }
+
+void hypfs_write_lock(void)
+{
+    write_lock(&hypfs_lock);
+}
+
+void hypfs_write_unlock(void)
+{
+    write_unlock(&hypfs_lock);
+}
diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index f8f41820d5..3b8b0d8ca5 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -198,7 +198,13 @@ static void __init _cmdline_parse(const char *cmdline)
 
 int runtime_parse(const char *line)
 {
-    return parse_params(line, __param_start, __param_end);
+    int ret;
+
+    hypfs_write_lock();
+    ret = parse_params(line, __param_start, __param_end);
+    hypfs_write_unlock();
+
+    return ret;
 }
 
 /**
@@ -429,6 +435,25 @@ static int __init buildinfo_init(void)
     return 0;
 }
 __initcall(buildinfo_init);
+
+static HYPFS_DIR_INIT(params, "params");
+
+static int __init param_init(void)
+{
+    struct param_hypfs *param;
+
+    hypfs_add_dir(&hypfs_root, &params, true);
+
+    for ( param = __paramhypfs_start; param < __paramhypfs_end; param++ )
+    {
+        if ( param->init_leaf )
+            param->init_leaf(param);
+        hypfs_add_leaf(&params, &param->hypfs, true);
+    }
+
+    return 0;
+}
+__initcall(param_init);
 #endif
 
 # define DO(fn) long do_##fn
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 913ae1b66a..692b7278f6 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -75,12 +75,35 @@ enum con_timestamp_mode
     TSM_DATE_MS,       /* [YYYY-MM-DD HH:MM:SS.mmm] */
     TSM_BOOT,          /* [SSSSSS.uuuuuu] */
     TSM_RAW,           /* [XXXXXXXXXXXXXXXX] */
+    TSM_END
 };
 
 static enum con_timestamp_mode __read_mostly opt_con_timestamp_mode = TSM_NONE;
 
+#ifdef CONFIG_HYPFS
+static const char con_timestamp_mode_2_string[TSM_END][7] = {
+    [TSM_NONE] = "none",
+    [TSM_DATE] = "date",
+    [TSM_DATE_MS] = "datems",
+    [TSM_BOOT] = "boot",
+    [TSM_RAW] = "raw"
+};
+
+static void con_timestamp_mode_upd(struct param_hypfs *par)
+{
+    const char *val = con_timestamp_mode_2_string[opt_con_timestamp_mode];
+
+    custom_runtime_set_var_sz(par, val, 7);
+}
+#else
+static void con_timestamp_mode_upd(struct param_hypfs *par)
+{
+}
+#endif
+
 static int parse_console_timestamps(const char *s);
-custom_runtime_param("console_timestamps", parse_console_timestamps);
+custom_runtime_param("console_timestamps", parse_console_timestamps,
+                     con_timestamp_mode_upd);
 
 /* conring_size: allows a large console ring than default (16kB). */
 static uint32_t __initdata opt_conring_size;
@@ -143,6 +166,39 @@ static int __read_mostly xenlog_guest_lower_thresh =
 static int parse_loglvl(const char *s);
 static int parse_guest_loglvl(const char *s);
 
+#ifdef CONFIG_HYPFS
+#define LOGLVL_VAL_SZ 16
+static char xenlog_val[LOGLVL_VAL_SZ];
+static char xenlog_guest_val[LOGLVL_VAL_SZ];
+
+static char *lvl2opt[] = { "none", "error", "warning", "info", "all" };
+
+static void xenlog_update_val(int lower, int upper, char *val)
+{
+    snprintf(val, LOGLVL_VAL_SZ, "%s/%s", lvl2opt[lower], lvl2opt[upper]);
+}
+
+static void __init xenlog_init(struct param_hypfs *par)
+{
+    xenlog_update_val(xenlog_lower_thresh, xenlog_upper_thresh, xenlog_val);
+    custom_runtime_set_var(par, xenlog_val);
+}
+
+static void __init xenlog_guest_init(struct param_hypfs *par)
+{
+    xenlog_update_val(xenlog_guest_lower_thresh, xenlog_guest_upper_thresh,
+                      xenlog_guest_val);
+    custom_runtime_set_var(par, xenlog_guest_val);
+}
+#else
+#define xenlog_val       NULL
+#define xenlog_guest_val NULL
+
+static void xenlog_update_val(int lower, int upper, char *val)
+{
+}
+#endif
+
 /*
  * <lvl> := none|error|warning|info|debug|all
  * loglvl=<lvl_print_always>[/<lvl_print_ratelimit>]
@@ -151,8 +207,8 @@ static int parse_guest_loglvl(const char *s);
  * Similar definitions for guest_loglvl, but applies to guest tracing.
  * Defaults: loglvl=warning ; guest_loglvl=none/warning
  */
-custom_runtime_param("loglvl", parse_loglvl);
-custom_runtime_param("guest_loglvl", parse_guest_loglvl);
+custom_runtime_param("loglvl", parse_loglvl, xenlog_init);
+custom_runtime_param("guest_loglvl", parse_guest_loglvl, xenlog_guest_init);
 
 static atomic_t print_everything = ATOMIC_INIT(0);
 
@@ -173,7 +229,7 @@ static int __parse_loglvl(const char *s, const char **ps)
     return 2; /* sane fallback */
 }
 
-static int _parse_loglvl(const char *s, int *lower, int *upper)
+static int _parse_loglvl(const char *s, int *lower, int *upper, char *val)
 {
     *lower = *upper = __parse_loglvl(s, &s);
     if ( *s == '/' )
@@ -181,18 +237,21 @@ static int _parse_loglvl(const char *s, int *lower, int 
*upper)
     if ( *upper < *lower )
         *upper = *lower;
 
+    xenlog_update_val(*lower, *upper, val);
+
     return *s ? -EINVAL : 0;
 }
 
 static int parse_loglvl(const char *s)
 {
-    return _parse_loglvl(s, &xenlog_lower_thresh, &xenlog_upper_thresh);
+    return _parse_loglvl(s, &xenlog_lower_thresh, &xenlog_upper_thresh,
+                         xenlog_val);
 }
 
 static int parse_guest_loglvl(const char *s)
 {
     return _parse_loglvl(s, &xenlog_guest_lower_thresh,
-                         &xenlog_guest_upper_thresh);
+                         &xenlog_guest_upper_thresh, xenlog_guest_val);
 }
 
 static char *loglvl_str(int lvl)
@@ -727,13 +786,17 @@ static int printk_prefix_check(char *p, char **pp)
 
 static int parse_console_timestamps(const char *s)
 {
+    struct param_hypfs *par = param_2_parfs(parse_console_timestamps);
+
     switch ( parse_bool(s, NULL) )
     {
     case 0:
         opt_con_timestamp_mode = TSM_NONE;
+        con_timestamp_mode_upd(par);
         return 0;
     case 1:
         opt_con_timestamp_mode = TSM_DATE;
+        con_timestamp_mode_upd(par);
         return 0;
     }
     if ( *s == '\0' || /* Compat for old booleanparam() */
@@ -750,6 +813,8 @@ static int parse_console_timestamps(const char *s)
     else
         return -EINVAL;
 
+    con_timestamp_mode_upd(par);
+
     return 0;
 }
 
diff --git a/xen/include/xen/hypfs.h b/xen/include/xen/hypfs.h
index 279bcf3b4c..095a0c9bee 100644
--- a/xen/include/xen/hypfs.h
+++ b/xen/include/xen/hypfs.h
@@ -117,6 +117,13 @@ int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
                      XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
 int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
                      XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
+int hypfs_write_custom(struct hypfs_entry_leaf *leaf,
+                       XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
+void hypfs_write_lock(void);
+void hypfs_write_unlock(void);
+#else
+static inline void hypfs_write_lock(void) {}
+static inline void hypfs_write_unlock(void) {}
 #endif
 
 #endif /* __XEN_HYPFS_H__ */
diff --git a/xen/include/xen/param.h b/xen/include/xen/param.h
index a1dc3ba8f0..4893de9bd5 100644
--- a/xen/include/xen/param.h
+++ b/xen/include/xen/param.h
@@ -1,6 +1,7 @@
 #ifndef _XEN_PARAM_H
 #define _XEN_PARAM_H
 
+#include <xen/hypfs.h>
 #include <xen/init.h>
 #include <xen/lib.h>
 #include <xen/stdbool.h>
@@ -80,7 +81,120 @@ extern const struct kernel_param __param_start[], 
__param_end[];
 
 #define __rtparam         __param(__dataparam)
 
-#define custom_runtime_only_param(_name, _var) \
+#ifdef CONFIG_HYPFS
+
+struct param_hypfs {
+    const struct kernel_param *param;
+    struct hypfs_entry_leaf hypfs;
+    void (*init_leaf)(struct param_hypfs *par);
+};
+
+extern struct param_hypfs __paramhypfs_start[], __paramhypfs_end[];
+
+#define __paramhypfs      __used_section(".data.paramhypfs")
+
+#define __paramfs         static __paramhypfs \
+    __attribute__((__aligned__(sizeof(void *)))) struct param_hypfs
+
+#define custom_runtime_set_var_sz(parfs, var, sz) \
+    { \
+        (parfs)->hypfs.content = var; \
+        (parfs)->hypfs.e.max_size = sz; \
+        (parfs)->hypfs.e.size = strlen(var) + 1; \
+    }
+#define custom_runtime_set_var(parfs, var) \
+    custom_runtime_set_var_sz(parfs, var, sizeof(var))
+
+#define param_2_parfs(par) &__parfs_##par
+
+/* initfunc needs to set size and content, e.g. via custom_runtime_set_var(). 
*/
+#define custom_runtime_only_param(_name, _var, initfunc) \
+    __rtparam __rtpar_##_var = \
+      { .name = _name, \
+          .type = OPT_CUSTOM, \
+          .par.func = _var }; \
+    __paramfs __parfs_##_var = \
+        { .param = &__rtpar_##_var, \
+          .init_leaf = initfunc, \
+          .hypfs.e.type = XEN_HYPFS_TYPE_STRING, \
+          .hypfs.e.encoding = XEN_HYPFS_ENC_PLAIN, \
+          .hypfs.e.name = _name, \
+          .hypfs.e.read = hypfs_read_leaf, \
+          .hypfs.e.write = hypfs_write_custom }
+#define boolean_runtime_only_param(_name, _var) \
+    __rtparam __rtpar_##_var = \
+        { .name = _name, \
+          .type = OPT_BOOL, \
+          .len = sizeof(_var) + \
+                 BUILD_BUG_ON_ZERO(sizeof(_var) != sizeof(bool)), \
+          .par.var = &_var }; \
+    __paramfs __parfs_##_var = \
+        { .param = &__rtpar_##_var, \
+          .hypfs.e.type = XEN_HYPFS_TYPE_BOOL, \
+          .hypfs.e.encoding = XEN_HYPFS_ENC_PLAIN, \
+          .hypfs.e.name = _name, \
+          .hypfs.e.size = sizeof(_var), \
+          .hypfs.e.max_size = sizeof(_var), \
+          .hypfs.e.read = hypfs_read_leaf, \
+          .hypfs.e.write = hypfs_write_bool, \
+          .hypfs.content = &_var }
+#define integer_runtime_only_param(_name, _var) \
+    __rtparam __rtpar_##_var = \
+        { .name = _name, \
+          .type = OPT_UINT, \
+          .len = sizeof(_var), \
+          .par.var = &_var }; \
+    __paramfs __parfs_##_var = \
+        { .param = &__rtpar_##_var, \
+          .hypfs.e.type = XEN_HYPFS_TYPE_UINT, \
+          .hypfs.e.encoding = XEN_HYPFS_ENC_PLAIN, \
+          .hypfs.e.name = _name, \
+          .hypfs.e.size = sizeof(_var), \
+          .hypfs.e.max_size = sizeof(_var), \
+          .hypfs.e.read = hypfs_read_leaf, \
+          .hypfs.e.write = hypfs_write_leaf, \
+          .hypfs.content = &_var }
+#define size_runtime_only_param(_name, _var) \
+    __rtparam __rtpar_##_var = \
+        { .name = _name, \
+          .type = OPT_SIZE, \
+          .len = sizeof(_var), \
+          .par.var = &_var }; \
+    __paramfs __parfs_##_var = \
+        { .param = &__rtpar_##_var, \
+          .hypfs.e.type = XEN_HYPFS_TYPE_UINT, \
+          .hypfs.e.encoding = XEN_HYPFS_ENC_PLAIN, \
+          .hypfs.e.name = _name, \
+          .hypfs.e.size = sizeof(_var), \
+          .hypfs.e.max_size = sizeof(_var), \
+          .hypfs.e.read = hypfs_read_leaf, \
+          .hypfs.e.write = hypfs_write_leaf, \
+          .hypfs.content = &_var }
+#define string_runtime_only_param(_name, _var) \
+    __rtparam __rtpar_##_var = \
+        { .name = _name, \
+          .type = OPT_STR, \
+          .len = sizeof(_var), \
+          .par.var = &_var }; \
+    __paramfs __parfs_##_var = \
+        { .param = &__rtpar_##_var, \
+          .hypfs.e.type = XEN_HYPFS_TYPE_STRING, \
+          .hypfs.e.encoding = XEN_HYPFS_ENC_PLAIN, \
+          .hypfs.e.name = _name, \
+          .hypfs.e.size = sizeof(_var), \
+          .hypfs.e.max_size = sizeof(_var), \
+          .hypfs.e.read = hypfs_read_leaf, \
+          .hypfs.e.write = hypfs_write_leaf, \
+          .hypfs.content = &_var }
+
+#else
+
+struct param_hypfs {
+};
+
+#define param_2_parfs(par)  NULL
+
+#define custom_runtime_only_param(_name, _var, initfunc) \
     __rtparam __rtpar_##_var = \
       { .name = _name, \
           .type = OPT_CUSTOM, \
@@ -111,9 +225,13 @@ extern const struct kernel_param __param_start[], 
__param_end[];
           .len = sizeof(_var), \
           .par.var = &_var }
 
-#define custom_runtime_param(_name, _var) \
+#define custom_runtime_set_var(parfs, var)
+
+#endif
+
+#define custom_runtime_param(_name, _var, initfunc) \
     custom_param(_name, _var); \
-    custom_runtime_only_param(_name, _var)
+    custom_runtime_only_param(_name, _var, initfunc)
 #define boolean_runtime_param(_name, _var) \
     boolean_param(_name, _var); \
     boolean_runtime_only_param(_name, _var)
-- 
2.26.1