* [PATCH v3 3/7] um: Define timers on a per-CPU basis
2025-09-14 15:56 [PATCH v3 0/7] um: Add SMP support Tiwei Bie
2025-09-14 15:56 ` [PATCH v3 1/7] um: Turn signals_* into thread-local variables Tiwei Bie
2025-09-14 15:56 ` [PATCH v3 2/7] um: Determine sleep based on need_resched() Tiwei Bie
@ 2025-09-14 15:56 ` Tiwei Bie
2025-09-14 15:56 ` [PATCH v3 4/7] um: Add initial SMP support Tiwei Bie
` (3 subsequent siblings)
6 siblings, 0 replies; 10+ messages in thread
From: Tiwei Bie @ 2025-09-14 15:56 UTC (permalink / raw)
To: richard, anton.ivanov, johannes
Cc: linux-um, linux-kernel, benjamin, arnd, tiwei.btw, tiwei.bie
From: Tiwei Bie <tiwei.btw@antgroup.com>
Define timers on a per-CPU basis to enable each CPU to have its
own timer. This is a preparation for adding SMP support.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
---
arch/um/include/linux/time-internal.h | 3 ++
arch/um/include/shared/os.h | 6 +--
arch/um/kernel/irq.c | 2 +-
arch/um/kernel/time.c | 58 +++++++++++++++++++--------
arch/um/os-Linux/main.c | 2 +-
arch/um/os-Linux/time.c | 29 +++++++++-----
6 files changed, 69 insertions(+), 31 deletions(-)
diff --git a/arch/um/include/linux/time-internal.h b/arch/um/include/linux/time-internal.h
index 138908b999d7..c274eb5ad55e 100644
--- a/arch/um/include/linux/time-internal.h
+++ b/arch/um/include/linux/time-internal.h
@@ -90,4 +90,7 @@ extern unsigned long tt_extra_sched_jiffies;
* which is intentional since we really shouldn't link it in that case.
*/
void time_travel_ndelay(unsigned long nsec);
+
+int um_setup_timer(void);
+
#endif /* __TIMER_INTERNAL_H__ */
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 324d4eed3385..0ca6e4548671 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -269,9 +269,9 @@ extern void os_warn(const char *fmt, ...)
/* time.c */
extern void os_idle_sleep(void);
extern int os_timer_create(void);
-extern int os_timer_set_interval(unsigned long long nsecs);
-extern int os_timer_one_shot(unsigned long long nsecs);
-extern void os_timer_disable(void);
+extern int os_timer_set_interval(int cpu, unsigned long long nsecs);
+extern int os_timer_one_shot(int cpu, unsigned long long nsecs);
+extern void os_timer_disable(int cpu);
extern long long os_persistent_clock_emulation(void);
extern long long os_nsecs(void);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index d69d137a0334..e95f6c5a259d 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -683,7 +683,7 @@ void __init init_IRQ(void)
{
int i;
- irq_set_chip_and_handler(TIMER_IRQ, &alarm_irq_type, handle_edge_irq);
+ irq_set_chip_and_handler(TIMER_IRQ, &alarm_irq_type, handle_percpu_irq);
for (i = 1; i < UM_LAST_SIGNAL_IRQ; i++)
irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 17da0a870650..b344a36b44eb 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -625,9 +625,10 @@ void time_travel_sleep(void)
* controller application.
*/
unsigned long long next = S64_MAX;
+ int cpu = raw_smp_processor_id();
if (time_travel_mode == TT_MODE_BASIC)
- os_timer_disable();
+ os_timer_disable(cpu);
time_travel_update_time(next, true);
@@ -638,9 +639,9 @@ void time_travel_sleep(void)
* This is somewhat wrong - we should get the first
* one sooner like the os_timer_one_shot() below...
*/
- os_timer_set_interval(time_travel_timer_interval);
+ os_timer_set_interval(cpu, time_travel_timer_interval);
} else {
- os_timer_one_shot(time_travel_timer_event.time - next);
+ os_timer_one_shot(cpu, time_travel_timer_event.time - next);
}
}
}
@@ -758,6 +759,8 @@ extern u64 time_travel_ext_req(u32 op, u64 time);
#define time_travel_del_event(e) do { } while (0)
#endif
+static struct clock_event_device timer_clockevent[NR_CPUS];
+
void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
{
unsigned long flags;
@@ -780,12 +783,14 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
static int itimer_shutdown(struct clock_event_device *evt)
{
+ int cpu = evt - &timer_clockevent[0];
+
if (time_travel_mode != TT_MODE_OFF)
time_travel_del_event(&time_travel_timer_event);
if (time_travel_mode != TT_MODE_INFCPU &&
time_travel_mode != TT_MODE_EXTERNAL)
- os_timer_disable();
+ os_timer_disable(cpu);
return 0;
}
@@ -793,6 +798,7 @@ static int itimer_shutdown(struct clock_event_device *evt)
static int itimer_set_periodic(struct clock_event_device *evt)
{
unsigned long long interval = NSEC_PER_SEC / HZ;
+ int cpu = evt - &timer_clockevent[0];
if (time_travel_mode != TT_MODE_OFF) {
time_travel_del_event(&time_travel_timer_event);
@@ -805,7 +811,7 @@ static int itimer_set_periodic(struct clock_event_device *evt)
if (time_travel_mode != TT_MODE_INFCPU &&
time_travel_mode != TT_MODE_EXTERNAL)
- os_timer_set_interval(interval);
+ os_timer_set_interval(cpu, interval);
return 0;
}
@@ -825,7 +831,7 @@ static int itimer_next_event(unsigned long delta,
if (time_travel_mode != TT_MODE_INFCPU &&
time_travel_mode != TT_MODE_EXTERNAL)
- return os_timer_one_shot(delta);
+ return os_timer_one_shot(raw_smp_processor_id(), delta);
return 0;
}
@@ -835,10 +841,9 @@ static int itimer_one_shot(struct clock_event_device *evt)
return itimer_next_event(0, evt);
}
-static struct clock_event_device timer_clockevent = {
+static struct clock_event_device _timer_clockevent = {
.name = "posix-timer",
.rating = 250,
- .cpumask = cpu_possible_mask,
.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT,
.set_state_shutdown = itimer_shutdown,
@@ -856,6 +861,9 @@ static struct clock_event_device timer_clockevent = {
static irqreturn_t um_timer(int irq, void *dev)
{
+ int cpu = raw_smp_processor_id();
+ struct clock_event_device *evt = &timer_clockevent[cpu];
+
/*
* Interrupt the (possibly) running userspace process, technically this
* should only happen if userspace is currently executing.
@@ -867,7 +875,7 @@ static irqreturn_t um_timer(int irq, void *dev)
get_current()->mm)
os_alarm_process(get_current()->mm->context.id.pid);
- (*timer_clockevent.event_handler)(&timer_clockevent);
+ evt->event_handler(evt);
return IRQ_HANDLED;
}
@@ -904,7 +912,24 @@ static struct clocksource timer_clocksource = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-static void __init um_timer_setup(void)
+int um_setup_timer(void)
+{
+ int cpu = raw_smp_processor_id();
+ struct clock_event_device *evt = &timer_clockevent[cpu];
+ int err;
+
+ err = os_timer_create();
+ if (err)
+ return err;
+
+ memcpy(evt, &_timer_clockevent, sizeof(*evt));
+ evt->cpumask = cpumask_of(cpu);
+ clockevents_register_device(evt);
+
+ return 0;
+}
+
+static void __init um_timer_init(void)
{
int err;
@@ -913,8 +938,8 @@ static void __init um_timer_setup(void)
printk(KERN_ERR "register_timer : request_irq failed - "
"errno = %d\n", -err);
- err = os_timer_create();
- if (err != 0) {
+ err = um_setup_timer();
+ if (err) {
printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
return;
}
@@ -924,7 +949,6 @@ static void __init um_timer_setup(void)
printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
return;
}
- clockevents_register_device(&timer_clockevent);
}
void read_persistent_clock64(struct timespec64 *ts)
@@ -945,7 +969,7 @@ void read_persistent_clock64(struct timespec64 *ts)
void __init time_init(void)
{
timer_set_signal_handler();
- late_time_init = um_timer_setup;
+ late_time_init = um_timer_init;
}
#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
@@ -961,21 +985,21 @@ static int setup_time_travel(char *str)
{
if (strcmp(str, "=inf-cpu") == 0) {
time_travel_mode = TT_MODE_INFCPU;
- timer_clockevent.name = "time-travel-timer-infcpu";
+ _timer_clockevent.name = "time-travel-timer-infcpu";
timer_clocksource.name = "time-travel-clock";
return 1;
}
if (strncmp(str, "=ext:", 5) == 0) {
time_travel_mode = TT_MODE_EXTERNAL;
- timer_clockevent.name = "time-travel-timer-external";
+ _timer_clockevent.name = "time-travel-timer-external";
timer_clocksource.name = "time-travel-clock-external";
return time_travel_connect_external(str + 5);
}
if (!*str) {
time_travel_mode = TT_MODE_BASIC;
- timer_clockevent.name = "time-travel-timer";
+ _timer_clockevent.name = "time-travel-timer";
timer_clocksource.name = "time-travel-clock";
return 1;
}
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index 3c63ce19e3bf..730723106228 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -171,7 +171,7 @@ int __init main(int argc, char **argv, char **envp)
*/
/* stop timers and set timer signal to be ignored */
- os_timer_disable();
+ os_timer_disable(0);
/* disable SIGIO for the fds and set SIGIO to be ignored */
err = deactivate_all_fds();
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index f3d4547e5227..e0197bfe4ac9 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -17,7 +17,7 @@
#include <string.h>
#include "internal.h"
-static timer_t event_high_res_timer = 0;
+static timer_t event_high_res_timer[CONFIG_NR_CPUS] = { 0 };
static inline long long timespec_to_ns(const struct timespec *ts)
{
@@ -32,20 +32,30 @@ long long os_persistent_clock_emulation(void)
return timespec_to_ns(&realtime_tp);
}
+#ifndef sigev_notify_thread_id
+#define sigev_notify_thread_id _sigev_un._tid
+#endif
+
/**
* os_timer_create() - create an new posix (interval) timer
*/
int os_timer_create(void)
{
- timer_t *t = &event_high_res_timer;
+ timer_t *t = &event_high_res_timer[0];
+ struct sigevent sev = {
+ .sigev_notify = SIGEV_THREAD_ID,
+ .sigev_signo = SIGALRM,
+ .sigev_value.sival_ptr = t,
+ .sigev_notify_thread_id = gettid(),
+ };
- if (timer_create(CLOCK_MONOTONIC, NULL, t) == -1)
+ if (timer_create(CLOCK_MONOTONIC, &sev, t) == -1)
return -1;
return 0;
}
-int os_timer_set_interval(unsigned long long nsecs)
+int os_timer_set_interval(int cpu, unsigned long long nsecs)
{
struct itimerspec its;
@@ -55,13 +65,13 @@ int os_timer_set_interval(unsigned long long nsecs)
its.it_interval.tv_sec = nsecs / UM_NSEC_PER_SEC;
its.it_interval.tv_nsec = nsecs % UM_NSEC_PER_SEC;
- if (timer_settime(event_high_res_timer, 0, &its, NULL) == -1)
+ if (timer_settime(event_high_res_timer[cpu], 0, &its, NULL) == -1)
return -errno;
return 0;
}
-int os_timer_one_shot(unsigned long long nsecs)
+int os_timer_one_shot(int cpu, unsigned long long nsecs)
{
struct itimerspec its = {
.it_value.tv_sec = nsecs / UM_NSEC_PER_SEC,
@@ -71,19 +81,20 @@ int os_timer_one_shot(unsigned long long nsecs)
.it_interval.tv_nsec = 0, // we cheat here
};
- timer_settime(event_high_res_timer, 0, &its, NULL);
+ timer_settime(event_high_res_timer[cpu], 0, &its, NULL);
return 0;
}
/**
* os_timer_disable() - disable the posix (interval) timer
+ * @cpu: the CPU for which the timer is to be disabled
*/
-void os_timer_disable(void)
+void os_timer_disable(int cpu)
{
struct itimerspec its;
memset(&its, 0, sizeof(struct itimerspec));
- timer_settime(event_high_res_timer, 0, &its, NULL);
+ timer_settime(event_high_res_timer[cpu], 0, &its, NULL);
}
long long os_nsecs(void)
--
2.34.1
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH v3 4/7] um: Add initial SMP support
2025-09-14 15:56 [PATCH v3 0/7] um: Add SMP support Tiwei Bie
` (2 preceding siblings ...)
2025-09-14 15:56 ` [PATCH v3 3/7] um: Define timers on a per-CPU basis Tiwei Bie
@ 2025-09-14 15:56 ` Tiwei Bie
2025-09-14 15:56 ` [PATCH v3 5/7] um: vdso: Remove getcpu support on x86 Tiwei Bie
` (2 subsequent siblings)
6 siblings, 0 replies; 10+ messages in thread
From: Tiwei Bie @ 2025-09-14 15:56 UTC (permalink / raw)
To: richard, anton.ivanov, johannes
Cc: linux-um, linux-kernel, benjamin, arnd, tiwei.btw, tiwei.bie
From: Tiwei Bie <tiwei.btw@antgroup.com>
Add initial symmetric multi-processing (SMP) support to UML. With
this support enabled, users can tell UML to start multiple virtual
processors, each represented as a separate host thread.
In UML, kthreads and normal threads (when running in kernel mode)
can be scheduled and executed simultaneously on different virtual
processors. However, the userspace code of normal threads still
runs within their respective single-threaded stubs.
That is, SMP support is currently available both within the kernel
and across different processes, but still remains limited within
threads of the same process in userspace.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
---
.../core/generic-idle-thread/arch-support.txt | 2 +-
arch/um/Kconfig | 46 +++-
arch/um/include/asm/current.h | 5 +-
arch/um/include/asm/hardirq.h | 24 +-
arch/um/include/asm/mmu.h | 10 +
arch/um/include/asm/pgtable.h | 2 +
arch/um/include/asm/smp.h | 15 +-
arch/um/include/linux/smp-internal.h | 17 ++
arch/um/include/shared/kern_util.h | 1 +
arch/um/include/shared/os.h | 17 ++
arch/um/include/shared/skas/mm_id.h | 5 +
arch/um/include/shared/smp.h | 20 ++
arch/um/kernel/Makefile | 1 +
arch/um/kernel/irq.c | 25 ++
arch/um/kernel/mem.c | 2 +
arch/um/kernel/process.c | 12 +-
arch/um/kernel/skas/mmu.c | 33 ++-
arch/um/kernel/skas/process.c | 7 +-
arch/um/kernel/smp.c | 241 ++++++++++++++++++
arch/um/kernel/tlb.c | 5 +-
arch/um/kernel/trap.c | 2 +-
arch/um/kernel/um_arch.c | 25 +-
arch/um/os-Linux/Makefile | 4 +-
arch/um/os-Linux/internal.h | 8 +
arch/um/os-Linux/main.c | 3 +-
arch/um/os-Linux/process.c | 20 ++
arch/um/os-Linux/signal.c | 31 ++-
arch/um/os-Linux/skas/process.c | 22 +-
arch/um/os-Linux/smp.c | 148 +++++++++++
arch/um/os-Linux/start_up.c | 4 +
arch/um/os-Linux/time.c | 38 ++-
31 files changed, 751 insertions(+), 44 deletions(-)
create mode 100644 arch/um/include/linux/smp-internal.h
create mode 100644 arch/um/include/shared/smp.h
create mode 100644 arch/um/kernel/smp.c
create mode 100644 arch/um/os-Linux/smp.c
diff --git a/Documentation/features/core/generic-idle-thread/arch-support.txt b/Documentation/features/core/generic-idle-thread/arch-support.txt
index 0735cb5367b4..425442e31fa2 100644
--- a/Documentation/features/core/generic-idle-thread/arch-support.txt
+++ b/Documentation/features/core/generic-idle-thread/arch-support.txt
@@ -24,7 +24,7 @@
| s390: | ok |
| sh: | ok |
| sparc: | ok |
- | um: | TODO |
+ | um: | ok |
| x86: | ok |
| xtensa: | ok |
-----------------------
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 8161cc5ae6f7..3d1b1fdbf3be 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -27,6 +27,7 @@ config UML
select OF_EARLY_FLATTREE if OF
select GENERIC_IRQ_SHOW
select GENERIC_CPU_DEVICES
+ select GENERIC_SMP_IDLE_THREAD
select HAVE_GCC_PLUGINS
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_LTO_CLANG_THIN
@@ -80,10 +81,48 @@ config HZ
int
default 100
-config NR_CPUS
+config UML_SUBARCH_SUPPORTS_SMP
+ bool
+
+config SMP
+ bool "Symmetric multi-processing support"
+ default n
+ depends on UML_SUBARCH_SUPPORTS_SMP
+ help
+ This option enables UML SMP support.
+
+ With this enabled, users can tell UML to start multiple virtual
+ processors. Each virtual processor is represented as a separate
+ host thread.
+
+ In UML, kthreads and normal threads (when running in kernel mode)
+ can be scheduled and executed simultaneously on different virtual
+ processors. However, the userspace code of normal threads still
+ runs within their respective single-threaded stubs.
+
+ That is, SMP support is available both within the kernel and
+ across different processes, but remains limited within threads
+ of the same process in userspace.
+
+config NR_CPUS_RANGE_BEGIN
int
- range 1 1
- default 1
+ default 1 if !SMP
+ default 2
+
+config NR_CPUS_RANGE_END
+ int
+ default 1 if !SMP
+ default 64
+
+config NR_CPUS_DEFAULT
+ int
+ default 1 if !SMP
+ default 2
+
+config NR_CPUS
+ int "Maximum number of CPUs" if SMP
+ range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
+ default NR_CPUS_DEFAULT
source "arch/$(HEADER_ARCH)/um/Kconfig"
@@ -259,6 +298,7 @@ source "arch/um/drivers/Kconfig"
config ARCH_SUSPEND_POSSIBLE
def_bool y
+ depends on !SMP
menu "Power management options"
diff --git a/arch/um/include/asm/current.h b/arch/um/include/asm/current.h
index 8accc6d6f502..159a29b3d4cc 100644
--- a/arch/um/include/asm/current.h
+++ b/arch/um/include/asm/current.h
@@ -7,15 +7,16 @@
#ifndef __ASSEMBLER__
+#include <shared/smp.h>
+
struct task_struct;
extern struct task_struct *cpu_tasks[NR_CPUS];
static __always_inline struct task_struct *get_current(void)
{
- return cpu_tasks[0];
+ return cpu_tasks[uml_curr_cpu()];
}
-
#define current get_current()
#endif /* __ASSEMBLER__ */
diff --git a/arch/um/include/asm/hardirq.h b/arch/um/include/asm/hardirq.h
index 52e2c36267a9..8de71752a9b8 100644
--- a/arch/um/include/asm/hardirq.h
+++ b/arch/um/include/asm/hardirq.h
@@ -2,8 +2,30 @@
#ifndef __ASM_UM_HARDIRQ_H
#define __ASM_UM_HARDIRQ_H
-#include <asm-generic/hardirq.h>
+#include <linux/cache.h>
+#include <linux/threads.h>
#define __ARCH_IRQ_EXIT_IRQS_DISABLED 1
+typedef struct {
+ unsigned int __softirq_pending;
+#if IS_ENABLED(CONFIG_SMP)
+ unsigned int irq_resched_count;
+ unsigned int irq_call_count;
+#endif
+} ____cacheline_aligned irq_cpustat_t;
+
+DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
+
+#define __ARCH_IRQ_STAT
+
+#define inc_irq_stat(member) this_cpu_inc(irq_stat.member)
+
+#include <linux/irq.h>
+
+static inline void ack_bad_irq(unsigned int irq)
+{
+ pr_crit("unexpected IRQ trap at vector %02x\n", irq);
+}
+
#endif /* __ASM_UM_HARDIRQ_H */
diff --git a/arch/um/include/asm/mmu.h b/arch/um/include/asm/mmu.h
index 4d0e4239f3cc..07d48738b402 100644
--- a/arch/um/include/asm/mmu.h
+++ b/arch/um/include/asm/mmu.h
@@ -7,16 +7,26 @@
#define __ARCH_UM_MMU_H
#include "linux/types.h"
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
#include <mm_id.h>
typedef struct mm_context {
struct mm_id id;
+ struct mutex turnstile;
struct list_head list;
/* Address range in need of a TLB sync */
+ spinlock_t sync_tlb_lock;
unsigned long sync_tlb_range_from;
unsigned long sync_tlb_range_to;
} mm_context_t;
+#define INIT_MM_CONTEXT(mm) \
+ .context = { \
+ .turnstile = __MUTEX_INITIALIZER(mm.context.turnstile), \
+ .sync_tlb_lock = __SPIN_LOCK_INITIALIZER(mm.context.sync_tlb_lock), \
+ }
+
#endif
diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index 24fdea6f88c3..91aec3698475 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -225,6 +225,8 @@ static inline void set_pte(pte_t *pteptr, pte_t pteval)
static inline void um_tlb_mark_sync(struct mm_struct *mm, unsigned long start,
unsigned long end)
{
+ guard(spinlock_irqsave)(&mm->context.sync_tlb_lock);
+
if (!mm->context.sync_tlb_range_to) {
mm->context.sync_tlb_range_from = start;
mm->context.sync_tlb_range_to = end;
diff --git a/arch/um/include/asm/smp.h b/arch/um/include/asm/smp.h
index a8cc1d46ddcb..be1743a6ff3c 100644
--- a/arch/um/include/asm/smp.h
+++ b/arch/um/include/asm/smp.h
@@ -2,6 +2,19 @@
#ifndef __UM_SMP_H
#define __UM_SMP_H
-#define hard_smp_processor_id() 0
+#if IS_ENABLED(CONFIG_SMP)
+
+#include <linux/cpumask.h>
+#include <shared/smp.h>
+
+#define raw_smp_processor_id() uml_curr_cpu()
+
+void arch_smp_send_reschedule(int cpu);
+
+void arch_send_call_function_single_ipi(int cpu);
+
+void arch_send_call_function_ipi_mask(const struct cpumask *mask);
+
+#endif /* CONFIG_SMP */
#endif
diff --git a/arch/um/include/linux/smp-internal.h b/arch/um/include/linux/smp-internal.h
new file mode 100644
index 000000000000..1dbcbc23f9c9
--- /dev/null
+++ b/arch/um/include/linux/smp-internal.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_SMP_INTERNAL_H
+#define __UM_SMP_INTERNAL_H
+
+#if IS_ENABLED(CONFIG_SMP)
+
+void prefill_possible_map(void);
+
+#else /* !CONFIG_SMP */
+
+static inline void prefill_possible_map(void) { }
+
+#endif /* CONFIG_SMP */
+
+extern char cpu_irqstacks[NR_CPUS][THREAD_SIZE] __aligned(THREAD_SIZE);
+
+#endif /* __UM_SMP_INTERNAL_H */
diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h
index 3daaa5c4b35d..14a8df1927a6 100644
--- a/arch/um/include/shared/kern_util.h
+++ b/arch/um/include/shared/kern_util.h
@@ -14,6 +14,7 @@ struct siginfo;
extern int uml_exitcode;
extern int kmalloc_ok;
+extern int kmalloc_disabled[];
#define UML_ROUND_UP(addr) \
((((unsigned long) addr) + PAGE_SIZE - 1) & PAGE_MASK)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 0ca6e4548671..b26e94292fc1 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -216,6 +216,9 @@ extern int can_drop_memory(void);
void os_set_pdeathsig(void);
+int os_futex_wait(void *uaddr, unsigned int val);
+int os_futex_wake(void *uaddr);
+
/* execvp.c */
extern int execvp_noalloc(char *buf, const char *file, char *const argv[]);
/* helper.c */
@@ -267,6 +270,7 @@ extern void os_warn(const char *fmt, ...)
__attribute__ ((format (printf, 1, 2)));
/* time.c */
+void os_idle_prepare(void);
extern void os_idle_sleep(void);
extern int os_timer_create(void);
extern int os_timer_set_interval(int cpu, unsigned long long nsecs);
@@ -339,4 +343,17 @@ extern void um_trace_signals_off(void);
/* time-travel */
extern void deliver_time_travel_irqs(void);
+/* smp.c */
+#if IS_ENABLED(CONFIG_SMP)
+void os_init_smp(void);
+int os_start_cpu_thread(int cpu);
+void os_start_secondary(void *arg, jmp_buf *switch_buf);
+int os_send_ipi(int cpu, int vector);
+void os_local_ipi_enable(void);
+void os_local_ipi_disable(void);
+#else /* !CONFIG_SMP */
+static inline void os_local_ipi_enable(void) { }
+static inline void os_local_ipi_disable(void) { }
+#endif /* CONFIG_SMP */
+
#endif
diff --git a/arch/um/include/shared/skas/mm_id.h b/arch/um/include/shared/skas/mm_id.h
index 4f977ef5dda5..fb96c0bd8222 100644
--- a/arch/um/include/shared/skas/mm_id.h
+++ b/arch/um/include/shared/skas/mm_id.h
@@ -6,6 +6,8 @@
#ifndef __MM_ID_H
#define __MM_ID_H
+#include <linux/compiler_types.h>
+
#define STUB_MAX_FDS 4
struct mm_id {
@@ -19,6 +21,9 @@ struct mm_id {
int syscall_fd_map[STUB_MAX_FDS];
};
+void enter_turnstile(struct mm_id *mm_id) __acquires(turnstile);
+void exit_turnstile(struct mm_id *mm_id) __releases(turnstile);
+
void notify_mm_kill(int pid);
#endif
diff --git a/arch/um/include/shared/smp.h b/arch/um/include/shared/smp.h
new file mode 100644
index 000000000000..06e3faa95091
--- /dev/null
+++ b/arch/um/include/shared/smp.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_SHARED_SMP_H
+#define __UM_SHARED_SMP_H
+
+#if IS_ENABLED(CONFIG_SMP)
+
+extern int uml_ncpus;
+
+int uml_curr_cpu(void);
+void uml_start_secondary(void *opaque);
+void uml_ipi_handler(int vector);
+
+#else /* !CONFIG_SMP */
+
+#define uml_ncpus 1
+#define uml_curr_cpu() 0
+
+#endif /* CONFIG_SMP */
+
+#endif /* __UM_SHARED_SMP_H */
diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
index b8f4e9281599..be60bc451b3f 100644
--- a/arch/um/kernel/Makefile
+++ b/arch/um/kernel/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_GPROF) += gprof_syms.o
obj-$(CONFIG_OF) += dtb.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
+obj-$(CONFIG_SMP) += smp.o
USER_OBJS := config.o
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index e95f6c5a259d..f4b13f15a9c1 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -22,6 +22,9 @@
#include <irq_kern.h>
#include <linux/time-internal.h>
+DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
+
+#define irq_stats(x) (&per_cpu(irq_stat, x))
/* When epoll triggers we do not know why it did so
* we can also have different IRQs for read and write.
@@ -701,3 +704,25 @@ void sigchld_handler(int sig, struct siginfo *unused_si,
{
do_IRQ(SIGCHLD_IRQ, regs);
}
+
+/*
+ * /proc/interrupts printing for arch specific interrupts
+ */
+int arch_show_interrupts(struct seq_file *p, int prec)
+{
+#if IS_ENABLED(CONFIG_SMP)
+ int cpu;
+
+ seq_printf(p, "%*s: ", prec, "RES");
+ for_each_online_cpu(cpu)
+ seq_printf(p, "%10u ", irq_stats(cpu)->irq_resched_count);
+ seq_puts(p, " Rescheduling interrupts\n");
+
+ seq_printf(p, "%*s: ", prec, "CAL");
+ for_each_online_cpu(cpu)
+ seq_printf(p, "%10u ", irq_stats(cpu)->irq_call_count);
+ seq_puts(p, " Function call interrupts\n");
+#endif
+
+ return 0;
+}
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 76bec7de81b5..d35c1bd225e0 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -53,6 +53,8 @@ pgd_t swapper_pg_dir[PTRS_PER_PGD];
/* Initialized at boot time, and readonly after that */
int kmalloc_ok = 0;
+int kmalloc_disabled[NR_CPUS];
+
/* Used during early boot */
static unsigned long brk_end;
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 41b3b3bf7309..16562a4a3f52 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -185,11 +185,12 @@ int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
void initial_thread_cb(void (*proc)(void *), void *arg)
{
- int save_kmalloc_ok = kmalloc_ok;
+ int cpu = raw_smp_processor_id();
+ int save_kmalloc = kmalloc_disabled[cpu];
- kmalloc_ok = 0;
+ kmalloc_disabled[cpu] = 1;
initial_thread_cb_skas(proc, arg);
- kmalloc_ok = save_kmalloc_ok;
+ kmalloc_disabled[cpu] = save_kmalloc;
}
int arch_dup_task_struct(struct task_struct *dst,
@@ -220,6 +221,11 @@ void arch_cpu_idle(void)
um_idle_sleep();
}
+void arch_cpu_idle_prepare(void)
+{
+ os_idle_prepare();
+}
+
int __uml_cant_sleep(void) {
return in_atomic() || irqs_disabled() || in_interrupt();
/* Is in_interrupt() really needed? */
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index afe9a2f251ef..00957788591b 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -23,17 +23,36 @@ static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
static spinlock_t mm_list_lock;
static struct list_head mm_list;
+void enter_turnstile(struct mm_id *mm_id) __acquires(turnstile)
+{
+ struct mm_context *ctx = container_of(mm_id, struct mm_context, id);
+
+ mutex_lock(&ctx->turnstile);
+}
+
+void exit_turnstile(struct mm_id *mm_id) __releases(turnstile)
+{
+ struct mm_context *ctx = container_of(mm_id, struct mm_context, id);
+
+ mutex_unlock(&ctx->turnstile);
+}
+
int init_new_context(struct task_struct *task, struct mm_struct *mm)
{
struct mm_id *new_id = &mm->context.id;
unsigned long stack = 0;
int ret = -ENOMEM;
+ mutex_init(&mm->context.turnstile);
+ spin_lock_init(&mm->context.sync_tlb_lock);
+
stack = __get_free_pages(GFP_KERNEL | __GFP_ZERO, ilog2(STUB_DATA_PAGES));
if (stack == 0)
goto out;
new_id->stack = stack;
+ new_id->syscall_data_len = 0;
+ new_id->syscall_fd_num = 0;
scoped_guard(spinlock_irqsave, &mm_list_lock) {
/* Insert into list, used for lookups when the child dies */
@@ -73,6 +92,9 @@ void destroy_context(struct mm_struct *mm)
return;
}
+ scoped_guard(spinlock_irqsave, &mm_list_lock)
+ list_del(&mm->context.list);
+
if (mmu->id.pid > 0) {
os_kill_ptraced_process(mmu->id.pid, 1);
mmu->id.pid = -1;
@@ -82,10 +104,6 @@ void destroy_context(struct mm_struct *mm)
os_close_file(mmu->id.sock);
free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES));
-
- guard(spinlock_irqsave)(&mm_list_lock);
-
- list_del(&mm->context.list);
}
static irqreturn_t mm_sigchld_irq(int irq, void* dev)
@@ -110,12 +128,11 @@ static irqreturn_t mm_sigchld_irq(int irq, void* dev)
/* Marks the MM as dead */
mm_context->id.pid = -1;
- /*
- * NOTE: If SMP is implemented, a futex_wake
- * needs to be added here.
- */
stub_data = (void *)mm_context->id.stack;
stub_data->futex = FUTEX_IN_KERN;
+#if IS_ENABLED(CONFIG_SMP)
+ os_futex_wake(&stub_data->futex);
+#endif
/*
* NOTE: Currently executing syscalls by
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index 5881b17eb987..444e82b5b7ee 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -7,6 +7,7 @@
#include <linux/sched/mm.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/task.h>
+#include <linux/smp-internal.h>
#include <asm/tlbflush.h>
@@ -26,12 +27,12 @@ static int __init start_kernel_proc(void *unused)
return 0;
}
-static char cpu0_irqstack[THREAD_SIZE] __aligned(THREAD_SIZE);
+char cpu_irqstacks[NR_CPUS][THREAD_SIZE] __aligned(THREAD_SIZE);
int __init start_uml(void)
{
- stack_protections((unsigned long) &cpu0_irqstack);
- set_sigstack(cpu0_irqstack, THREAD_SIZE);
+ stack_protections((unsigned long) &cpu_irqstacks[0]);
+ set_sigstack(cpu_irqstacks[0], THREAD_SIZE);
init_new_thread_signals();
diff --git a/arch/um/kernel/smp.c b/arch/um/kernel/smp.c
new file mode 100644
index 000000000000..b47c57d55d17
--- /dev/null
+++ b/arch/um/kernel/smp.c
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Ant Group
+ * Author: Tiwei Bie <tiwei.btw@antgroup.com>
+ *
+ * Based on the previous implementation in TT mode
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/sched.h>
+#include <linux/sched/task.h>
+#include <linux/sched/task_stack.h>
+#include <linux/module.h>
+#include <linux/processor.h>
+#include <linux/threads.h>
+#include <linux/cpu.h>
+#include <linux/hardirq.h>
+#include <linux/smp.h>
+#include <linux/smp-internal.h>
+#include <init.h>
+#include <kern.h>
+#include <os.h>
+#include <smp.h>
+
+enum {
+ UML_IPI_RES = 0,
+ UML_IPI_CALL_SINGLE,
+ UML_IPI_CALL,
+ UML_IPI_STOP,
+};
+
+void arch_smp_send_reschedule(int cpu)
+{
+ os_send_ipi(cpu, UML_IPI_RES);
+}
+
+void arch_send_call_function_single_ipi(int cpu)
+{
+ os_send_ipi(cpu, UML_IPI_CALL_SINGLE);
+}
+
+void arch_send_call_function_ipi_mask(const struct cpumask *mask)
+{
+ int cpu;
+
+ for_each_cpu(cpu, mask)
+ os_send_ipi(cpu, UML_IPI_CALL);
+}
+
+void smp_send_stop(void)
+{
+ int cpu, me = smp_processor_id();
+
+ for_each_online_cpu(cpu) {
+ if (cpu == me)
+ continue;
+ os_send_ipi(cpu, UML_IPI_STOP);
+ }
+}
+
+static void ipi_handler(int vector, struct uml_pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
+ int cpu = raw_smp_processor_id();
+
+ irq_enter();
+
+ if (current->mm)
+ os_alarm_process(current->mm->context.id.pid);
+
+ switch (vector) {
+ case UML_IPI_RES:
+ inc_irq_stat(irq_resched_count);
+ scheduler_ipi();
+ break;
+
+ case UML_IPI_CALL_SINGLE:
+ inc_irq_stat(irq_call_count);
+ generic_smp_call_function_single_interrupt();
+ break;
+
+ case UML_IPI_CALL:
+ inc_irq_stat(irq_call_count);
+ generic_smp_call_function_interrupt();
+ break;
+
+ case UML_IPI_STOP:
+ set_cpu_online(cpu, false);
+ while (1)
+ pause();
+ break;
+
+ default:
+ pr_err("CPU#%d received unknown IPI (vector=%d)!\n", cpu, vector);
+ break;
+ }
+
+ irq_exit();
+ set_irq_regs(old_regs);
+}
+
+void uml_ipi_handler(int vector)
+{
+ struct uml_pt_regs r = { .is_user = 0 };
+
+ preempt_disable();
+ ipi_handler(vector, &r);
+ preempt_enable();
+}
+
+/* AP states used only during CPU startup */
+enum {
+ UML_CPU_PAUSED = 0,
+ UML_CPU_RUNNING,
+};
+
+static int cpu_states[NR_CPUS];
+
+static int start_secondary(void *unused)
+{
+ int err, cpu = raw_smp_processor_id();
+
+ notify_cpu_starting(cpu);
+ set_cpu_online(cpu, true);
+
+ err = um_setup_timer();
+ if (err)
+ panic("CPU#%d failed to setup timer, err = %d", cpu, err);
+
+ local_irq_enable();
+
+ cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
+ return 0;
+}
+
+void uml_start_secondary(void *opaque)
+{
+ int cpu = raw_smp_processor_id();
+ struct mm_struct *mm = &init_mm;
+ struct task_struct *idle;
+
+ stack_protections((unsigned long) &cpu_irqstacks[cpu]);
+ set_sigstack(&cpu_irqstacks[cpu], THREAD_SIZE);
+
+ set_cpu_present(cpu, true);
+ os_futex_wait(&cpu_states[cpu], UML_CPU_PAUSED);
+
+ smp_rmb(); /* paired with smp_wmb() in __cpu_up() */
+
+ idle = cpu_tasks[cpu];
+ idle->thread_info.cpu = cpu;
+
+ mmgrab(mm);
+ idle->active_mm = mm;
+
+ idle->thread.request.thread.proc = start_secondary;
+ idle->thread.request.thread.arg = NULL;
+
+ new_thread(task_stack_page(idle), &idle->thread.switch_buf,
+ new_thread_handler);
+ os_start_secondary(opaque, &idle->thread.switch_buf);
+}
+
+void __init smp_prepare_cpus(unsigned int max_cpus)
+{
+ int err, cpu, me = smp_processor_id();
+ unsigned long deadline;
+
+ os_init_smp();
+
+ for_each_possible_cpu(cpu) {
+ if (cpu == me)
+ continue;
+
+ pr_debug("Booting processor %d...\n", cpu);
+ err = os_start_cpu_thread(cpu);
+ if (err) {
+ pr_crit("CPU#%d failed to start cpu thread, err = %d",
+ cpu, err);
+ continue;
+ }
+
+ deadline = jiffies + msecs_to_jiffies(1000);
+ spin_until_cond(cpu_present(cpu) ||
+ time_is_before_jiffies(deadline));
+
+ if (!cpu_present(cpu))
+ pr_crit("CPU#%d failed to boot\n", cpu);
+ }
+}
+
+int __cpu_up(unsigned int cpu, struct task_struct *tidle)
+{
+ cpu_tasks[cpu] = tidle;
+ smp_wmb(); /* paired with smp_rmb() in uml_start_secondary() */
+ cpu_states[cpu] = UML_CPU_RUNNING;
+ os_futex_wake(&cpu_states[cpu]);
+ spin_until_cond(cpu_online(cpu));
+
+ return 0;
+}
+
+void __init smp_cpus_done(unsigned int max_cpus)
+{
+}
+
+/* Set in uml_ncpus_setup */
+int uml_ncpus = 1;
+
+void __init prefill_possible_map(void)
+{
+ int cpu;
+
+ for (cpu = 0; cpu < uml_ncpus; cpu++)
+ set_cpu_possible(cpu, true);
+ for (; cpu < NR_CPUS; cpu++)
+ set_cpu_possible(cpu, false);
+}
+
+static int __init uml_ncpus_setup(char *line, int *add)
+{
+ *add = 0;
+
+ if (kstrtoint(line, 10, ¨_ncpus)) {
+ os_warn("%s: Couldn't parse '%s'\n", __func__, line);
+ return -1;
+ }
+
+ uml_ncpus = clamp(uml_ncpus, 1, NR_CPUS);
+
+ return 0;
+}
+
+__uml_setup("ncpus=", uml_ncpus_setup,
+"ncpus=<# of desired CPUs>\n"
+" This tells UML how many virtual processors to start. The maximum\n"
+" number of supported virtual processors can be obtained by querying\n"
+" the CONFIG_NR_CPUS option using --showconfig.\n\n"
+);
+
+EXPORT_SYMBOL(uml_curr_cpu);
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index cf7e0d4407f2..39608cccf2c6 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -162,9 +162,11 @@ int um_tlb_sync(struct mm_struct *mm)
{
pgd_t *pgd;
struct vm_ops ops;
- unsigned long addr = mm->context.sync_tlb_range_from, next;
+ unsigned long addr, next;
int ret = 0;
+ guard(spinlock_irqsave)(&mm->context.sync_tlb_lock);
+
if (mm->context.sync_tlb_range_to == 0)
return 0;
@@ -177,6 +179,7 @@ int um_tlb_sync(struct mm_struct *mm)
ops.unmap = unmap;
}
+ addr = mm->context.sync_tlb_range_from;
pgd = pgd_offset(mm, addr);
do {
next = pgd_addr_end(addr, mm->context.sync_tlb_range_to);
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 5b80a3a89c20..177615820a4c 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -316,7 +316,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
if (!is_user && regs)
current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
- if (!is_user && init_mm.context.sync_tlb_range_to) {
+ if (!is_user && address >= start_vm && address < end_vm) {
/*
* Kernel has pending updates from set_ptes that were not
* flushed yet. Syncing them should fix the pagefault (if not
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index cfbbbf8500c3..a6890e908a5d 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -19,6 +19,7 @@
#include <linux/kmsg_dump.h>
#include <linux/suspend.h>
#include <linux/random.h>
+#include <linux/smp-internal.h>
#include <asm/processor.h>
#include <asm/cpufeature.h>
@@ -71,6 +72,12 @@ static int show_cpuinfo(struct seq_file *m, void *v)
{
int i = 0;
+#if IS_ENABLED(CONFIG_SMP)
+ i = (uintptr_t) v - 1;
+ if (!cpu_online(i))
+ return 0;
+#endif
+
seq_printf(m, "processor\t: %d\n", i);
seq_printf(m, "vendor_id\t: User Mode Linux\n");
seq_printf(m, "model name\t: UML\n");
@@ -87,13 +94,14 @@ static int show_cpuinfo(struct seq_file *m, void *v)
loops_per_jiffy/(500000/HZ),
(loops_per_jiffy/(5000/HZ)) % 100);
-
return 0;
}
static void *c_start(struct seq_file *m, loff_t *pos)
{
- return *pos < nr_cpu_ids ? &boot_cpu_data + *pos : NULL;
+ if (*pos < nr_cpu_ids)
+ return (void *)(uintptr_t)(*pos + 1);
+ return NULL;
}
static void *c_next(struct seq_file *m, void *v, loff_t *pos)
@@ -421,6 +429,7 @@ void __init setup_arch(char **cmdline_p)
strscpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
*cmdline_p = command_line;
setup_hostinfo(host_info, sizeof host_info);
+ prefill_possible_map();
if (os_getrandom(rng_seed, sizeof(rng_seed), 0) == sizeof(rng_seed)) {
add_bootloader_randomness(rng_seed, sizeof(rng_seed));
@@ -455,6 +464,18 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
}
+#if IS_ENABLED(CONFIG_SMP)
+void alternatives_smp_module_add(struct module *mod, char *name,
+ void *locks, void *locks_end,
+ void *text, void *text_end)
+{
+}
+
+void alternatives_smp_module_del(struct module *mod)
+{
+}
+#endif
+
void *text_poke(void *addr, const void *opcode, size_t len)
{
/*
diff --git a/arch/um/os-Linux/Makefile b/arch/um/os-Linux/Makefile
index fae836713487..70c73c22f715 100644
--- a/arch/um/os-Linux/Makefile
+++ b/arch/um/os-Linux/Makefile
@@ -16,8 +16,10 @@ CFLAGS_main.o += -Wno-frame-larger-than
obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
+obj-$(CONFIG_SMP) += smp.o
+
USER_OBJS := $(user-objs-y) elf_aux.o execvp.o file.o helper.o irq.o \
main.o mem.o process.o registers.o sigio.o signal.o start_up.o time.o \
- tty.o umid.o util.o
+ tty.o umid.o util.o smp.o
include $(srctree)/arch/um/scripts/Makefile.rules
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
index c2c7a0dc673c..bac9fcc8c14c 100644
--- a/arch/um/os-Linux/internal.h
+++ b/arch/um/os-Linux/internal.h
@@ -4,6 +4,7 @@
#include <mm_id.h>
#include <stub-data.h>
+#include <signal.h>
/*
* elf_aux.c
@@ -18,6 +19,7 @@ void check_tmpexec(void);
/*
* signal.c
*/
+extern __thread int signals_enabled;
int timer_alarm_pending(void);
/*
@@ -25,4 +27,10 @@ int timer_alarm_pending(void);
*/
void wait_stub_done(int pid);
void wait_stub_done_seccomp(struct mm_id *mm_idp, int running, int wait_sigsys);
+
+/*
+ * smp.c
+ */
+#define IPI_SIGNAL SIGRTMIN
+
#endif /* __UM_OS_LINUX_INTERNAL_H */
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index 730723106228..f46a0b30a2a1 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -16,6 +16,7 @@
#include <init.h>
#include <kern_util.h>
#include <os.h>
+#include <smp.h>
#include <um_malloc.h>
#include "internal.h"
@@ -207,7 +208,7 @@ void *__wrap_malloc(int size)
{
void *ret;
- if (!kmalloc_ok)
+ if (!kmalloc_ok || kmalloc_disabled[uml_curr_cpu()])
return __real_malloc(size);
else if (size <= UM_KERN_PAGE_SIZE)
/* finding contiguous pages can be hard*/
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 00b49e90d05f..3a2a84ab9325 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -10,6 +10,8 @@
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
+#include <limits.h>
+#include <linux/futex.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/prctl.h>
@@ -189,3 +191,21 @@ void os_set_pdeathsig(void)
{
prctl(PR_SET_PDEATHSIG, SIGKILL);
}
+
+int os_futex_wait(void *uaddr, unsigned int val)
+{
+ int r;
+
+ CATCH_EINTR(r = syscall(__NR_futex, uaddr, FUTEX_WAIT, val,
+ NULL, NULL, 0));
+ return r < 0 ? -errno : r;
+}
+
+int os_futex_wake(void *uaddr)
+{
+ int r;
+
+ CATCH_EINTR(r = syscall(__NR_futex, uaddr, FUTEX_WAKE, INT_MAX,
+ NULL, NULL, 0));
+ return r < 0 ? -errno : r;
+}
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 554a87dd32cc..327fb3c52fc7 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -69,7 +69,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
#define SIGCHLD_BIT 2
#define SIGCHLD_MASK (1 << SIGCHLD_BIT)
-static __thread int signals_enabled;
+__thread int signals_enabled;
#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
static int signals_blocked, signals_blocked_pending;
#endif
@@ -259,9 +259,29 @@ int change_sig(int signal, int on)
return 0;
}
-void block_signals(void)
+static inline void __block_signals(void)
{
+ if (!signals_enabled)
+ return;
+
+ os_local_ipi_disable();
+ barrier();
signals_enabled = 0;
+}
+
+static inline void __unblock_signals(void)
+{
+ if (signals_enabled)
+ return;
+
+ signals_enabled = 1;
+ barrier();
+ os_local_ipi_enable();
+}
+
+void block_signals(void)
+{
+ __block_signals();
/*
* This must return with signals disabled, so this barrier
* ensures that writes are flushed out before the return.
@@ -278,7 +298,8 @@ void unblock_signals(void)
if (signals_enabled == 1)
return;
- signals_enabled = 1;
+ __unblock_signals();
+
#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
deliver_time_travel_irqs();
#endif
@@ -312,7 +333,7 @@ void unblock_signals(void)
* tracing that happens inside the handlers we call for the
* pending signals will mess up the tracing state.
*/
- signals_enabled = 0;
+ __block_signals();
um_trace_signals_off();
/*
@@ -344,7 +365,7 @@ void unblock_signals(void)
/* Re-enable signals and trace that we're doing so. */
um_trace_signals_on();
- signals_enabled = 1;
+ __unblock_signals();
}
}
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 0bc10cd4cbed..1c4c0dd17f7f 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -553,7 +553,7 @@ extern unsigned long tt_extra_sched_jiffies;
void userspace(struct uml_pt_regs *regs)
{
int err, status, op;
- siginfo_t si_ptrace;
+ siginfo_t si_local;
siginfo_t *si;
int sig;
@@ -563,6 +563,13 @@ void userspace(struct uml_pt_regs *regs)
while (1) {
struct mm_id *mm_id = current_mm_id();
+ /*
+ * At any given time, only one CPU thread can enter the
+ * turnstile to operate on the same stub process, including
+ * executing stub system calls (mmap and munmap).
+ */
+ enter_turnstile(mm_id);
+
/*
* When we are in time-travel mode, userspace can theoretically
* do a *lot* of work without being scheduled. The problem with
@@ -630,9 +637,10 @@ void userspace(struct uml_pt_regs *regs)
}
if (proc_data->si_offset > sizeof(proc_data->sigstack) - sizeof(*si))
- panic("%s - Invalid siginfo offset from child",
- __func__);
- si = (void *)&proc_data->sigstack[proc_data->si_offset];
+ panic("%s - Invalid siginfo offset from child", __func__);
+
+ si = &si_local;
+ memcpy(si, &proc_data->sigstack[proc_data->si_offset], sizeof(*si));
regs->is_user = 1;
@@ -728,8 +736,8 @@ void userspace(struct uml_pt_regs *regs)
case SIGFPE:
case SIGWINCH:
ptrace(PTRACE_GETSIGINFO, pid, 0,
- (struct siginfo *)&si_ptrace);
- si = &si_ptrace;
+ (struct siginfo *)&si_local);
+ si = &si_local;
break;
default:
si = NULL;
@@ -740,6 +748,8 @@ void userspace(struct uml_pt_regs *regs)
}
}
+ exit_turnstile(mm_id);
+
UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
if (sig) {
diff --git a/arch/um/os-Linux/smp.c b/arch/um/os-Linux/smp.c
new file mode 100644
index 000000000000..18d3858a7cd2
--- /dev/null
+++ b/arch/um/os-Linux/smp.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Ant Group
+ * Author: Tiwei Bie <tiwei.btw@antgroup.com>
+ */
+
+#include <errno.h>
+#include <pthread.h>
+#include <signal.h>
+#include <kern_util.h>
+#include <um_malloc.h>
+#include <init.h>
+#include <os.h>
+#include <smp.h>
+#include "internal.h"
+
+struct cpu_thread_data {
+ int cpu;
+ sigset_t sigset;
+};
+
+static __thread int __curr_cpu;
+
+int uml_curr_cpu(void)
+{
+ return __curr_cpu;
+}
+
+static pthread_t cpu_threads[CONFIG_NR_CPUS];
+
+static void *cpu_thread(void *arg)
+{
+ struct cpu_thread_data *data = arg;
+
+ __curr_cpu = data->cpu;
+
+ uml_start_secondary(data);
+
+ return NULL;
+}
+
+int os_start_cpu_thread(int cpu)
+{
+ struct cpu_thread_data *data;
+ sigset_t sigset, oset;
+ int err;
+
+ data = uml_kmalloc(sizeof(*data), UM_GFP_ATOMIC);
+ if (!data)
+ return -ENOMEM;
+
+ sigfillset(&sigset);
+ if (sigprocmask(SIG_SETMASK, &sigset, &oset) < 0) {
+ err = errno;
+ goto err;
+ }
+
+ data->cpu = cpu;
+ data->sigset = oset;
+
+ err = pthread_create(&cpu_threads[cpu], NULL, cpu_thread, data);
+ if (sigprocmask(SIG_SETMASK, &oset, NULL) < 0)
+ panic("Failed to restore the signal mask, errno = %d", errno);
+ if (err != 0)
+ goto err;
+
+ return 0;
+
+err:
+ kfree(data);
+ return -err;
+}
+
+void os_start_secondary(void *arg, jmp_buf *switch_buf)
+{
+ struct cpu_thread_data *data = arg;
+
+ sigaddset(&data->sigset, IPI_SIGNAL);
+ sigaddset(&data->sigset, SIGIO);
+
+ if (sigprocmask(SIG_SETMASK, &data->sigset, NULL) < 0)
+ panic("Failed to restore the signal mask, errno = %d", errno);
+
+ kfree(data);
+ longjmp(*switch_buf, 1);
+
+ /* unreachable */
+ printk(UM_KERN_ERR "impossible long jump!");
+ fatal_sigsegv();
+}
+
+int os_send_ipi(int cpu, int vector)
+{
+ union sigval value = { .sival_int = vector };
+
+ return pthread_sigqueue(cpu_threads[cpu], IPI_SIGNAL, value);
+}
+
+static void __local_ipi_set(int enable)
+{
+ sigset_t sigset;
+
+ sigemptyset(&sigset);
+ sigaddset(&sigset, IPI_SIGNAL);
+
+ if (sigprocmask(enable ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
+ panic("%s: sigprocmask failed, errno = %d", __func__, errno);
+}
+
+void os_local_ipi_enable(void)
+{
+ __local_ipi_set(1);
+}
+
+void os_local_ipi_disable(void)
+{
+ __local_ipi_set(0);
+}
+
+static void ipi_sig_handler(int sig, siginfo_t *si, void *uc)
+{
+ int save_errno = errno;
+
+ signals_enabled = 0;
+ um_trace_signals_off();
+
+ uml_ipi_handler(si->si_value.sival_int);
+
+ um_trace_signals_on();
+ signals_enabled = 1;
+
+ errno = save_errno;
+}
+
+void __init os_init_smp(void)
+{
+ struct sigaction action = {
+ .sa_sigaction = ipi_sig_handler,
+ .sa_flags = SA_SIGINFO | SA_ONSTACK | SA_RESTART,
+ };
+
+ sigfillset(&action.sa_mask);
+
+ if (sigaction(IPI_SIGNAL, &action, NULL) < 0)
+ panic("%s: sigaction failed, errno = %d", __func__, errno);
+
+ cpu_threads[0] = pthread_self();
+}
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index a827c2e01aa5..61c61e9c246c 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -22,6 +22,7 @@
#include <asm/unistd.h>
#include <init.h>
#include <os.h>
+#include <smp.h>
#include <kern_util.h>
#include <mem_user.h>
#include <ptrace_user.h>
@@ -481,6 +482,9 @@ void __init os_early_checks(void)
fatal("SECCOMP userspace requested but not functional!\n");
}
+ if (uml_ncpus > 1)
+ fatal("SMP is not supported with PTRACE userspace.\n");
+
using_seccomp = 0;
check_ptrace();
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index e0197bfe4ac9..e6aaf5e84f2f 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -11,9 +11,11 @@
#include <errno.h>
#include <signal.h>
#include <time.h>
+#include <sys/signalfd.h>
#include <sys/time.h>
#include <kern_util.h>
#include <os.h>
+#include <smp.h>
#include <string.h>
#include "internal.h"
@@ -41,7 +43,8 @@ long long os_persistent_clock_emulation(void)
*/
int os_timer_create(void)
{
- timer_t *t = &event_high_res_timer[0];
+ int cpu = uml_curr_cpu();
+ timer_t *t = &event_high_res_timer[cpu];
struct sigevent sev = {
.sigev_notify = SIGEV_THREAD_ID,
.sigev_signo = SIGALRM,
@@ -105,24 +108,49 @@ long long os_nsecs(void)
return timespec_to_ns(&ts);
}
+static __thread int wake_signals;
+
+void os_idle_prepare(void)
+{
+ sigset_t set;
+
+ sigemptyset(&set);
+ sigaddset(&set, SIGALRM);
+ sigaddset(&set, IPI_SIGNAL);
+
+ /*
+ * We need to use signalfd rather than sigsuspend in idle sleep
+ * because the IPI signal is a real‑time signal that carries data,
+ * and unlike handling SIGALRM, we cannot simply flag it in
+ * signals_pending.
+ */
+ wake_signals = signalfd(-1, &set, SFD_CLOEXEC);
+ if (wake_signals < 0)
+ panic("Failed to create signal FD, errno = %d", errno);
+}
+
/**
* os_idle_sleep() - sleep until interrupted
*/
void os_idle_sleep(void)
{
- sigset_t set, old;
+ sigset_t set;
- /* Block SIGALRM while performing the need_resched check. */
+ /*
+ * Block SIGALRM while performing the need_resched check.
+ * Note that, because IRQs are disabled, the IPI signal is
+ * already blocked.
+ */
sigemptyset(&set);
sigaddset(&set, SIGALRM);
- sigprocmask(SIG_BLOCK, &set, &old);
+ sigprocmask(SIG_BLOCK, &set, NULL);
/*
* Because disabling IRQs does not block SIGALRM, it is also
* necessary to check for any pending timer alarms.
*/
if (!uml_need_resched() && !timer_alarm_pending())
- sigsuspend(&old);
+ os_poll(1, &wake_signals);
/* Restore the signal mask. */
sigprocmask(SIG_UNBLOCK, &set, NULL);
--
2.34.1
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