[src/trunk]: src/sys/arch/x86/x86 Add a machdep.tsc_user_enable sysctl, to en...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/e2aad9a9f4de
branches:  trunk
changeset: 356554:e2aad9a9f4de
user:      maxv <maxv%NetBSD.org@localhost>
date:      Mon Oct 02 19:23:16 2017 +0000

description:
Add a machdep.tsc_user_enable sysctl, to enable/disable the rdtsc
instruction in usermode. It defaults to enabled.

diffstat:

 sys/arch/x86/x86/tsc.c         |  36 +++++++++++++++++++++++++++++-
 sys/arch/x86/x86/tsc.h         |   4 ++-
 sys/arch/x86/x86/x86_machdep.c |  49 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 84 insertions(+), 5 deletions(-)

diffs (177 lines):

diff -r 7a9383c78805 -r e2aad9a9f4de sys/arch/x86/x86/tsc.c
--- a/sys/arch/x86/x86/tsc.c    Mon Oct 02 17:48:01 2017 +0000
+++ b/sys/arch/x86/x86/tsc.c    Mon Oct 02 19:23:16 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tsc.c,v 1.36 2013/12/18 03:20:19 msaitoh Exp $ */
+/*     $NetBSD: tsc.c,v 1.37 2017/10/02 19:23:16 maxv Exp $    */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.36 2013/12/18 03:20:19 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.37 2017/10/02 19:23:16 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -37,6 +37,7 @@
 #include <sys/atomic.h>
 #include <sys/kernel.h>
 #include <sys/cpu.h>
+#include <sys/xcall.h>
 
 #include <machine/cpu_counter.h>
 #include <machine/cpuvar.h>
@@ -53,6 +54,8 @@
 static int64_t tsc_drift_observed;
 static bool    tsc_good;
 
+int tsc_user_enabled = 1;
+
 static volatile int64_t        tsc_sync_val;
 static volatile struct cpu_info        *tsc_sync_cpu;
 
@@ -265,6 +268,35 @@
        tsc_post_ap(ci);
 }
 
+static void
+tsc_apply_cpu(void *arg1, void *arg2)
+{
+       bool enable = (bool)arg1;
+       if (enable) {
+               lcr4(rcr4() & ~CR4_TSD);
+       } else {
+               lcr4(rcr4() | CR4_TSD);
+       }
+}
+
+void
+tsc_user_enable(void)
+{
+       uint64_t xc;
+
+       xc = xc_broadcast(0, tsc_apply_cpu, (void *)true, NULL);
+       xc_wait(xc);
+}
+
+void
+tsc_user_disable(void)
+{
+       uint64_t xc;
+
+       xc = xc_broadcast(0, tsc_apply_cpu, (void *)false, NULL);
+       xc_wait(xc);
+}
+
 uint64_t
 cpu_frequency(struct cpu_info *ci)
 {
diff -r 7a9383c78805 -r e2aad9a9f4de sys/arch/x86/x86/tsc.h
--- a/sys/arch/x86/x86/tsc.h    Mon Oct 02 17:48:01 2017 +0000
+++ b/sys/arch/x86/x86/tsc.h    Mon Oct 02 19:23:16 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tsc.h,v 1.5 2013/12/11 02:14:08 msaitoh Exp $  */
+/*     $NetBSD: tsc.h,v 1.6 2017/10/02 19:23:16 maxv Exp $     */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -31,3 +31,5 @@
 void   tsc_sync_ap(struct cpu_info *);
 void   tsc_sync_bp(struct cpu_info *);
 void   tsc_sync_drift(int64_t);
+void   tsc_user_enable(void);
+void   tsc_user_disable(void);
diff -r 7a9383c78805 -r e2aad9a9f4de sys/arch/x86/x86/x86_machdep.c
--- a/sys/arch/x86/x86/x86_machdep.c    Mon Oct 02 17:48:01 2017 +0000
+++ b/sys/arch/x86/x86/x86_machdep.c    Mon Oct 02 19:23:16 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: x86_machdep.c,v 1.95 2017/09/30 12:01:56 maxv Exp $    */
+/*     $NetBSD: x86_machdep.c,v 1.96 2017/10/02 19:23:16 maxv Exp $    */
 
 /*-
  * Copyright (c) 2002, 2006, 2007 YAMAMOTO Takashi,
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.95 2017/09/30 12:01:56 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.96 2017/10/02 19:23:16 maxv Exp $");
 
 #include "opt_modular.h"
 #include "opt_physmem.h"
@@ -70,6 +70,8 @@
 
 #include <uvm/uvm_extern.h>
 
+#include "tsc.h"
+
 #include "acpica.h"
 #if NACPICA > 0
 #include <dev/acpi/acpivar.h>
@@ -1109,6 +1111,38 @@
        return sysctl_lookup(SYSCTLFN_CALL(&node));
 }
 
+#ifndef XEN
+static int
+sysctl_machdep_tsc_enable(SYSCTLFN_ARGS)
+{
+       struct sysctlnode node;
+       int error, val;
+
+       val = *(int *)rnode->sysctl_data;
+
+       node = *rnode;
+       node.sysctl_data = &val;
+
+       error = sysctl_lookup(SYSCTLFN_CALL(&node));
+       if (error != 0 || newp == NULL)
+               return error;
+
+       if (val == 1) {
+               tsc_user_enable();
+       } else if (val == 0) {
+               tsc_user_disable();
+       } else {
+               error = EINVAL;
+       }
+       if (error)
+               return error;
+
+       *(int *)rnode->sysctl_data = val;
+
+       return 0;
+}
+#endif
+
 static void
 const_sysctl(struct sysctllog **clog, const char *name, int type,
     u_quad_t value, int tag)
@@ -1122,6 +1156,9 @@
 SYSCTL_SETUP(sysctl_machdep_setup, "sysctl machdep subtree setup")
 {
        extern uint64_t tsc_freq;
+#ifndef XEN
+       extern int tsc_user_enabled;
+#endif
        extern int sparse_dump;
 
        sysctl_createv(clog, 0, NULL, NULL,
@@ -1167,6 +1204,14 @@
                       SYSCTL_DESCR("Whether the kernel uses PAE"),
                       NULL, 0, &use_pae, 0,
                       CTL_MACHDEP, CTL_CREATE, CTL_EOL);
+#ifndef XEN
+       sysctl_createv(clog, 0, NULL, NULL,
+                      CTLFLAG_READWRITE,
+                      CTLTYPE_INT, "tsc_user_enable",
+                      SYSCTL_DESCR("RDTSC instruction enabled in usermode"),
+                      sysctl_machdep_tsc_enable, 0, &tsc_user_enabled, 0,
+                      CTL_MACHDEP, CTL_CREATE, CTL_EOL);
+#endif
 
        /* None of these can ever change once the system has booted */
        const_sysctl(clog, "fpu_present", CTLTYPE_INT, i386_fpu_present,