[src/trunk]: src/sys/arch/x86/x86 Add a workaround for local APIC timers runn...

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

details:   https://anonhg.NetBSD.org/src/rev/089b9b9e9e03
branches:  trunk
changeset: 828031:089b9b9e9e03
user:      jmcneill <jmcneill%NetBSD.org@localhost>
date:      Thu Nov 23 19:53:20 2017 +0000

description:
Add a workaround for local APIC timers running under KVM. It seems these
timers don't reload the current-count register in periodic mode when it
reaches 0, so we need to detect this condition and reload it ourselves.

XXX pullup

diffstat:

 sys/arch/x86/x86/lapic.c |  22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diffs (57 lines):

diff -r 0f6e910160d6 -r 089b9b9e9e03 sys/arch/x86/x86/lapic.c
--- a/sys/arch/x86/x86/lapic.c  Thu Nov 23 16:30:50 2017 +0000
+++ b/sys/arch/x86/x86/lapic.c  Thu Nov 23 19:53:20 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lapic.c,v 1.63 2017/11/04 12:53:00 maxv Exp $  */
+/*     $NetBSD: lapic.c,v 1.64 2017/11/23 19:53:20 jmcneill Exp $      */
 
 /*-
  * Copyright (c) 2000, 2008 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: lapic.c,v 1.63 2017/11/04 12:53:00 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: lapic.c,v 1.64 2017/11/23 19:53:20 jmcneill Exp $");
 
 #include "acpica.h"
 #include "ioapic.h"
@@ -124,6 +124,8 @@
 bool x2apic_enable = false;
 #endif
 
+static bool lapic_broken_periodic __read_mostly;
+
 static uint32_t
 i82489_readreg(u_int reg)
 {
@@ -678,6 +680,16 @@
                            32;
 
                /*
+                * Apply workaround for broken periodic timer under KVM
+                */
+               if (vm_guest == VM_GUEST_KVM) {
+                       lapic_broken_periodic = true;
+                       lapic_timecounter.tc_quality = -100;
+                       aprint_debug_dev(ci->ci_dev,
+                           "applying KVM timer workaround\n");
+               }
+
+               /*
                 * Now that the timer's calibrated, use the apic timer routines
                 * for all our timing needs..
                 */
@@ -717,6 +729,12 @@
 
        while (deltat > 0) {
                xtick = lapic_gettick();
+               if (lapic_broken_periodic && xtick == 0 && otick == 0) {
+                       lapic_initclocks();
+                       xtick = lapic_gettick();
+                       if (xtick == 0)
+                               panic("lapic timer stopped ticking");
+               }
                if (xtick > otick)
                        deltat -= lapic_tval - (xtick - otick);
                else