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Handle broadcast NMIs.

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On several Intel chipsets, diagnostic NMIs sent from BMC or NMIs
reporting hardware errors are broadcasted to all CPUs.

When kernel is configured to enter kdb on NMI, the outcome is
problematic, because each CPU tries to enter kdb.  All CPUs are
executing NMI handlers, which set the latches disabling the nested NMI
delivery; this means that stop_cpus_hard(), used by kdb_enter() to
stop other cpus by broadcasting IPI_STOP_HARD NMI, cannot work.  One
indication of this is the harmless but annoying diagnostic "timeout
stopping cpus".

Much more harming behaviour is that because all CPUs try to enter kdb,
and if ddb is used as debugger, all CPUs issue prompt on console and
race for the input, not to mention the simultaneous use of the ddb
shared state.

Try to fix this by introducing a pseudo-lock for simultaneous attempts
to handle NMIs.  If one core happens to enter NMI trap handler, other
cores see it and simulate reception of the IPI_STOP_HARD.  More,
generic_stop_cpus() avoids sending IPI_STOP_HARD and avoids waiting
for the acknowledgement, relying on the nmi handler on other cores
suspending and then restarting the CPU.

Since it is impossible to detect at runtime whether some stray NMI is
broadcast or unicast, add a knob for administrator (really developer)
to configure debugging NMI handling mode.

The updated patch was debugged with the help from Andrey Gapon (avg)
and discussed with him.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D8249
This commit is contained in:
Konstantin Belousov 2016-10-24 16:40:27 +00:00
parent 1d1140af58
commit 835c2787be
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=307866
7 changed files with 135 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
sys/amd64/amd64/trap.c
View File

@ -144,11 +144,6 @@ static char *trap_msg[] = {
"DTrace pid return trap", /* 32 T_DTRACE_RET */
};
#ifdef KDB
static int kdb_on_nmi = 1;
SYSCTL_INT(_machdep, OID_AUTO, kdb_on_nmi, CTLFLAG_RWTUN,
&kdb_on_nmi, 0, "Go to KDB on NMI");
#endif
static int panic_on_nmi = 1;
SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RWTUN,
&panic_on_nmi, 0, "Panic on NMI");
@ -377,21 +372,7 @@ trap(struct trapframe *frame)
#ifdef DEV_ISA
case T_NMI:
/* machine/parity/power fail/"kitchen sink" faults */
if (isa_nmi(frame->tf_err) == 0) {
#ifdef KDB
/*
* NMI can be hooked up to a pushbutton
* for debugging.
*/
if (kdb_on_nmi) {
printf ("NMI ... going to debugger\n");
kdb_trap(type, 0, frame);
}
#endif /* KDB */
goto userout;
} else if (panic_on_nmi)
panic("NMI indicates hardware failure");
nmi_handle_intr(type, frame, true);
break;
#endif /* DEV_ISA */
@ -563,20 +544,8 @@ trap(struct trapframe *frame)
#ifdef DEV_ISA
case T_NMI:
/* machine/parity/power fail/"kitchen sink" faults */
if (isa_nmi(frame->tf_err) == 0) {
#ifdef KDB
/*
* NMI can be hooked up to a pushbutton
* for debugging.
*/
if (kdb_on_nmi) {
printf ("NMI ... going to debugger\n");
kdb_trap(type, 0, frame);
}
#endif /* KDB */
goto out;
} else if (panic_on_nmi == 0)
if (nmi_handle_intr(type, frame, false) ||
!panic_on_nmi)
goto out;
/* FALLTHROUGH */
#endif /* DEV_ISA */

32
sys/i386/i386/trap.c
View File

@ -467,21 +467,7 @@ trap(struct trapframe *frame)
}
goto userout;
#else /* !POWERFAIL_NMI */
/* machine/parity/power fail/"kitchen sink" faults */
if (isa_nmi(frame->tf_err) == 0) {
#ifdef KDB
/*
* NMI can be hooked up to a pushbutton
* for debugging.
*/
if (kdb_on_nmi) {
printf ("NMI ... going to debugger\n");
kdb_trap(type, 0, frame);
}
#endif /* KDB */
goto userout;
} else if (panic_on_nmi)
panic("NMI indicates hardware failure");
nmi_handle_intr(type, frame, true);
break;
#endif /* POWERFAIL_NMI */
#endif /* DEV_ISA */
@ -730,20 +716,8 @@ trap(struct trapframe *frame)
}
goto out;
#else /* !POWERFAIL_NMI */
/* machine/parity/power fail/"kitchen sink" faults */
if (isa_nmi(frame->tf_err) == 0) {
#ifdef KDB
/*
* NMI can be hooked up to a pushbutton
* for debugging.
*/
if (kdb_on_nmi) {
printf ("NMI ... going to debugger\n");
kdb_trap(type, 0, frame);
}
#endif /* KDB */
goto out;
} else if (panic_on_nmi == 0)
if (nmi_handle_intr(type, frame, false) ||
!panic_on_nmi)
goto out;
/* FALLTHROUGH */
#endif /* POWERFAIL_NMI */

53
sys/kern/subr_smp.c
View File

@ -209,6 +209,11 @@ forward_signal(struct thread *td)
* 1: ok
*
*/
#if defined(__amd64__) || defined(__i386__)
#define X86 1
#else
#define X86 0
#endif
static int
generic_stop_cpus(cpuset_t map, u_int type)
{
@ -220,12 +225,11 @@ generic_stop_cpus(cpuset_t map, u_int type)
volatile cpuset_t *cpus;
KASSERT(
#if defined(__amd64__) || defined(__i386__)
type == IPI_STOP || type == IPI_STOP_HARD || type == IPI_SUSPEND,
#else
type == IPI_STOP || type == IPI_STOP_HARD,
type == IPI_STOP || type == IPI_STOP_HARD
#if X86
|| type == IPI_SUSPEND
#endif
("%s: invalid stop type", __func__));
, ("%s: invalid stop type", __func__));
if (!smp_started)
return (0);
@ -233,7 +237,7 @@ generic_stop_cpus(cpuset_t map, u_int type)
CTR2(KTR_SMP, "stop_cpus(%s) with %u type",
cpusetobj_strprint(cpusetbuf, &map), type);
#if defined(__amd64__) || defined(__i386__)
#if X86
/*
* When suspending, ensure there are are no IPIs in progress.
* IPIs that have been issued, but not yet delivered (e.g.
@ -245,6 +249,9 @@ generic_stop_cpus(cpuset_t map, u_int type)
mtx_lock_spin(&smp_ipi_mtx);
#endif
#if X86
if (!nmi_is_broadcast || nmi_kdb_lock == 0) {
#endif
if (stopping_cpu != PCPU_GET(cpuid))
while (atomic_cmpset_int(&stopping_cpu, NOCPU,
PCPU_GET(cpuid)) == 0)
@ -253,8 +260,11 @@ generic_stop_cpus(cpuset_t map, u_int type)
/* send the stop IPI to all CPUs in map */
ipi_selected(map, type);
#if X86
}
#endif
#if defined(__amd64__) || defined(__i386__)
#if X86
if (type == IPI_SUSPEND)
cpus = &suspended_cpus;
else
@ -272,7 +282,7 @@ generic_stop_cpus(cpuset_t map, u_int type)
}
}
#if defined(__amd64__) || defined(__i386__)
#if X86
if (type == IPI_SUSPEND)
mtx_unlock_spin(&smp_ipi_mtx);
#endif
@ -295,7 +305,7 @@ stop_cpus_hard(cpuset_t map)
return (generic_stop_cpus(map, IPI_STOP_HARD));
}
#if defined(__amd64__) || defined(__i386__)
#if X86
int
suspend_cpus(cpuset_t map)
{
@ -325,20 +335,18 @@ generic_restart_cpus(cpuset_t map, u_int type)
#endif
volatile cpuset_t *cpus;
KASSERT(
#if defined(__amd64__) || defined(__i386__)
type == IPI_STOP || type == IPI_STOP_HARD || type == IPI_SUSPEND,
#else
type == IPI_STOP || type == IPI_STOP_HARD,
KASSERT(type == IPI_STOP || type == IPI_STOP_HARD
#if X86
|| type == IPI_SUSPEND
#endif
("%s: invalid stop type", __func__));
, ("%s: invalid stop type", __func__));
if (!smp_started)
return 0;
return (0);
CTR1(KTR_SMP, "restart_cpus(%s)", cpusetobj_strprint(cpusetbuf, &map));
#if defined(__amd64__) || defined(__i386__)
#if X86
if (type == IPI_SUSPEND)
cpus = &suspended_cpus;
else
@ -348,11 +356,17 @@ generic_restart_cpus(cpuset_t map, u_int type)
/* signal other cpus to restart */
CPU_COPY_STORE_REL(&map, &started_cpus);
#if X86
if (!nmi_is_broadcast || nmi_kdb_lock == 0) {
#endif
/* wait for each to clear its bit */
while (CPU_OVERLAP(cpus, &map))
cpu_spinwait();
#if X86
}
#endif
return 1;
return (1);
}
int
@ -362,7 +376,7 @@ restart_cpus(cpuset_t map)
return (generic_restart_cpus(map, IPI_STOP));
}
#if defined(__amd64__) || defined(__i386__)
#if X86
int
resume_cpus(cpuset_t map)
{
@ -370,6 +384,7 @@ resume_cpus(cpuset_t map)
return (generic_restart_cpus(map, IPI_SUSPEND));
}
#endif
#undef X86
/*
* All-CPU rendezvous. CPUs are signalled, all execute the setup function

3
sys/x86/include/x86_smp.h
View File

@ -45,6 +45,9 @@ extern u_int ipi_page;
extern u_int ipi_range;
extern u_int ipi_range_size;
extern int nmi_kdb_lock;
extern int nmi_is_broadcast;
struct cpu_info {
int cpu_present:1;
int cpu_bsp:1;

5
sys/x86/include/x86_var.h
View File

@ -85,6 +85,7 @@ struct reg;
struct fpreg;
struct dbreg;
struct dumperinfo;
struct trapframe;
/*
* The interface type of the interrupt handler entry point cannot be
@ -107,6 +108,10 @@ bool fix_cpuid(void);
void fillw(int /*u_short*/ pat, void *base, size_t cnt);
int is_physical_memory(vm_paddr_t addr);
int isa_nmi(int cd);
bool nmi_call_kdb(u_int cpu, u_int type, struct trapframe *frame,
bool panic);
bool nmi_call_kdb_smp(u_int type, struct trapframe *frame, bool panic);
int nmi_handle_intr(u_int type, struct trapframe *frame, bool panic);
void pagecopy(void *from, void *to);
void printcpuinfo(void);
int user_dbreg_trap(void);

50
sys/x86/x86/cpu_machdep.c
View File

@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_inet.h"
#include "opt_isa.h"
#include "opt_kdb.h"
#include "opt_kstack_pages.h"
#include "opt_maxmem.h"
#include "opt_mp_watchdog.h"
@ -522,3 +523,52 @@ idle_sysctl(SYSCTL_HANDLER_ARGS)
SYSCTL_PROC(_machdep, OID_AUTO, idle, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
idle_sysctl, "A", "currently selected idle function");
int nmi_is_broadcast = 1;
SYSCTL_INT(_machdep, OID_AUTO, nmi_is_broadcast, CTLFLAG_RWTUN,
&nmi_is_broadcast, 0,
"Chipset NMI is broadcast");
#ifdef KDB
int kdb_on_nmi = 1;
SYSCTL_INT(_machdep, OID_AUTO, kdb_on_nmi, CTLFLAG_RWTUN,
&kdb_on_nmi, 0,
"Go to KDB on NMI");
#endif
#ifdef DEV_ISA
bool
nmi_call_kdb(u_int cpu, u_int type, struct trapframe *frame, bool do_panic)
{
/* machine/parity/power fail/"kitchen sink" faults */
if (isa_nmi(frame->tf_err) == 0) {
#ifdef KDB
/*
* NMI can be hooked up to a pushbutton for debugging.
*/
if (kdb_on_nmi) {
printf ("NMI/cpu%d ... going to debugger\n", cpu);
kdb_trap(type, 0, frame);
return (true);
}
} else
#endif /* KDB */
if (do_panic)
panic("NMI indicates hardware failure");
return (false);
}
#endif
int
nmi_handle_intr(u_int type, struct trapframe *frame, bool panic)
{
#ifdef DEV_ISA
#ifdef SMP
if (nmi_is_broadcast)
return (nmi_call_kdb_smp(type, frame, panic));
else
#endif
return (nmi_call_kdb(0, type, frame, panic));
#endif
}

37
sys/x86/x86/mp_x86.c
View File

@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$");
#include "opt_apic.h"
#endif
#include "opt_cpu.h"
#include "opt_isa.h"
#include "opt_kstack_pages.h"
#include "opt_pmap.h"
#include "opt_sched.h"
@ -140,6 +141,7 @@ int cpu_apic_ids[MAXCPU];
volatile u_int cpu_ipi_pending[MAXCPU];
static void release_aps(void *dummy);
static void cpustop_handler_post(u_int cpu);
static int hyperthreading_allowed = 1;
SYSCTL_INT(_machdep, OID_AUTO, hyperthreading_allowed, CTLFLAG_RDTUN,
@ -1211,6 +1213,34 @@ ipi_nmi_handler(void)
return (0);
}
#ifdef DEV_ISA
int nmi_kdb_lock;
bool
nmi_call_kdb_smp(u_int type, struct trapframe *frame, bool do_panic)
{
int cpu;
bool call_post, ret;
cpu = PCPU_GET(cpuid);
if (atomic_cmpset_acq_int(&nmi_kdb_lock, 0, 1)) {
ret = nmi_call_kdb(cpu, type, frame, do_panic);
call_post = false;
} else {
ret = true;
savectx(&stoppcbs[cpu]);
CPU_SET_ATOMIC(cpu, &stopped_cpus);
while (!atomic_cmpset_acq_int(&nmi_kdb_lock, 0, 1))
ia32_pause();
call_post = true;
}
atomic_store_rel_int(&nmi_kdb_lock, 0);
if (call_post)
cpustop_handler_post(cpu);
return (ret);
}
#endif
/*
* Handle an IPI_STOP by saving our current context and spinning until we
* are resumed.
@ -1231,6 +1261,13 @@ cpustop_handler(void)
while (!CPU_ISSET(cpu, &started_cpus))
ia32_pause();
cpustop_handler_post(cpu);
}
static void
cpustop_handler_post(u_int cpu)
{
CPU_CLR_ATOMIC(cpu, &started_cpus);
CPU_CLR_ATOMIC(cpu, &stopped_cpus);