Merge tag 'uml-for-linux-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull UML updates from Johannes Berg:
 "Apart from the usual small churn, we have

   - initial SMP support (only kernel)

   - major vDSO cleanups (and fixes for 32-bit)"

* tag 'uml-for-linux-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (33 commits)
  um: Disable KASAN_INLINE when STATIC_LINK is selected
  um: Don't rename vmap to kernel_vmap
  um: drivers: virtio: use string choices helper
  um: Always set up AT_HWCAP and AT_PLATFORM
  x86/um: Remove FIXADDR_USER_START and FIXADDR_USE_END
  um: Remove __access_ok_vsyscall()
  um: Remove redundant range check from __access_ok_vsyscall()
  um: Remove fixaddr_user_init()
  x86/um: Drop gate area handling
  x86/um: Do not inherit vDSO from host
  um: Split out default elf_aux_hwcap
  x86/um: Move ELF_PLATFORM fallback to x86-specific code
  um: Split out default elf_aux_platform
  um: Avoid circular dependency on asm-offsets in pgtable.h
  um: Enable SMP support on x86
  asm-generic: percpu: Add assembly guard
  um: vdso: Remove getcpu support on x86
  um: Add initial SMP support
  um: Define timers on a per-CPU basis
  um: Determine sleep based on need_resched()
  ...

Author: torvalds

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  |
     -----------------------

arch/um/Kconfig

@@ -5,6 +5,7 @@ menu "UML-specific options"
 config UML
 	bool
 	default y
+	select ARCH_DISABLE_KASAN_INLINE if STATIC_LINK
 	select ARCH_NEEDS_DEFER_KASAN if STATIC_LINK
 	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	select ARCH_HAS_CACHE_LINE_SIZE
@@ -28,6 +29,7 @@ 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
@@ -81,10 +83,48 @@ 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"
 
@@ -200,12 +240,6 @@ config KERNEL_STACK_ORDER
 	  increase in the size of the state which needs to be saved when handling
 	  signals.
 
-config MMAPPER
-	tristate "iomem emulation driver"
-	help
-	  This driver allows a host file to be used as emulated IO memory inside
-	  UML.
-
 config PGTABLE_LEVELS
 	int
 	default 4 if 64BIT
@@ -260,6 +294,7 @@ source "arch/um/drivers/Kconfig"
 
 config ARCH_SUSPEND_POSSIBLE
 	def_bool y
+	depends on !SMP
 
 menu "Power management options"
 

arch/um/Makefile

@@ -46,19 +46,17 @@ ARCH_INCLUDE	:= -I$(srctree)/$(SHARED_HEADERS)
 ARCH_INCLUDE	+= -I$(srctree)/$(HOST_DIR)/um/shared
 KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/um
 
-# -Dvmap=kernel_vmap prevents anything from referencing the libpcap.o symbol so
-# named - it's a common symbol in libpcap, so we get a binary which crashes.
-#
-# Same things for in6addr_loopback and mktime - found in libc. For these two we
-# only get link-time error, luckily.
+# -Dstrrchr=kernel_strrchr (as well as the various in6addr symbols) prevents
+#  anything from referencing
+# libc symbols with the same name, which can cause a linker error.
 #
 # -Dlongjmp=kernel_longjmp prevents anything from referencing the libpthread.a
 # embedded copy of longjmp, same thing for setjmp.
 #
-# These apply to USER_CFLAGS to.
+# These apply to USER_CFLAGS too.
 
 KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \
-	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap	\
+	$(ARCH_INCLUDE) $(MODE_INCLUDE)	\
 	-Dlongjmp=kernel_longjmp -Dsetjmp=kernel_setjmp \
 	-Din6addr_loopback=kernel_in6addr_loopback \
 	-Din6addr_any=kernel_in6addr_any -Dstrrchr=kernel_strrchr \

arch/um/drivers/Makefile

@@ -29,7 +29,6 @@ obj-$(CONFIG_STDERR_CONSOLE) += stderr_console.o
 
 obj-$(CONFIG_UML_NET_VECTOR) += vector.o
 obj-$(CONFIG_MCONSOLE) += mconsole.o
-obj-$(CONFIG_MMAPPER) += mmapper_kern.o 
 obj-$(CONFIG_BLK_DEV_UBD) += ubd.o 
 obj-$(CONFIG_UML_SOUND) += hostaudio.o
 obj-$(CONFIG_NULL_CHAN) += null.o 

arch/um/drivers/mmapper_kern.c

@@ -24,6 +24,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/string_choices.h>
 #include <linux/virtio.h>
 #include <linux/virtio_config.h>
 #include <linux/virtio_ring.h>
@@ -1151,8 +1152,7 @@ void virtio_uml_set_no_vq_suspend(struct virtio_device *vdev,
 		return;
 
 	vu_dev->no_vq_suspend = no_vq_suspend;
-	dev_info(&vdev->dev, "%sabled VQ suspend\n",
-		 no_vq_suspend ? "dis" : "en");
+	dev_info(&vdev->dev, "%s VQ suspend\n", str_disabled_enabled(no_vq_suspend));
 }
 
 static void vu_of_conn_broken(struct work_struct *wk)

arch/um/drivers/virtio_uml.c

@@ -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__ */

arch/um/include/asm/current.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 */

arch/um/include/asm/hardirq.h

@@ -2,15 +2,15 @@
 #ifndef __UM_IRQFLAGS_H
 #define __UM_IRQFLAGS_H
 
-extern int signals_enabled;
+int um_get_signals(void);
 int um_set_signals(int enable);
 void block_signals(void);
 void unblock_signals(void);
 
 #define arch_local_save_flags arch_local_save_flags
 static inline unsigned long arch_local_save_flags(void)
 {
-	return signals_enabled;
+	return um_get_signals();
 }
 
 #define arch_local_irq_restore arch_local_irq_restore

arch/um/include/asm/irqflags.h

@@ -24,10 +24,6 @@
 
 #ifdef CONFIG_KASAN
 void kasan_init(void);
-
-#if defined(CONFIG_STATIC_LINK) && defined(CONFIG_KASAN_INLINE)
-#error UML does not work in KASAN_INLINE mode with STATIC_LINK enabled!
-#endif
 #else
 static inline void kasan_init(void) { }
 #endif /* CONFIG_KASAN */