In order to facilitate parallel startup, start to eliminate some of the
global variables passing information to CPUs in the startup path.
However, start by introducing one more: smpboot_control. For now this
merely holds the CPU# of the CPU which is coming up. Each CPU can then
find its own per-cpu data, and everything else it needs can be found
from there, allowing the other global variables to be removed.
First to be removed is initial_stack. Each CPU can load %rsp from its
current_task->thread.sp instead. That is already set up with the correct
idle thread for APs. Set up the .sp field in INIT_THREAD on x86 so that
the BSP also finds a suitable stack pointer in the static per-cpu data
when coming up on first boot.
On resume from S3, the CPU needs a temporary stack because its idle task
is already active. Instead of setting initial_stack, the sleep code can
simply set its own current->thread.sp to point to the temporary stack.
Nobody else cares about ->thread.sp for a thread which is currently on
a CPU, because the true value is actually in the %rsp register. Which
is restored with the rest of the CPU context in do_suspend_lowlevel().
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Usama Arif <usama.arif@bytedance.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20230316222109.1940300-7-usama.arif@bytedance.com
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
#else
-#define INIT_THREAD { }
+extern unsigned long __end_init_task[];
+
+#define INIT_THREAD { \
+ .sp = (unsigned long)&__end_init_task - sizeof(struct pt_regs), \
+}
extern unsigned long KSTK_ESP(struct task_struct *task);
#define nmi_selftest() do { } while (0)
#endif
-#endif /* __ASSEMBLY__ */
+extern unsigned int smpboot_control;
+
+#endif /* !__ASSEMBLY__ */
+
#endif /* _ASM_X86_SMP_H */
saved_magic = 0x12345678;
#else /* CONFIG_64BIT */
#ifdef CONFIG_SMP
- initial_stack = (unsigned long)temp_stack + sizeof(temp_stack);
+ /*
+ * As each CPU starts up, it will find its own stack pointer
+ * from its current_task->thread.sp. Typically that will be
+ * the idle thread for a newly-started AP, or even the boot
+ * CPU which will find it set to &init_task in the static
+ * per-cpu data.
+ *
+ * Make the resuming CPU use the temporary stack at startup
+ * by setting current->thread.sp to point to that. The true
+ * %rsp will be restored with the rest of the CPU context,
+ * by do_suspend_lowlevel(). And unwinders don't care about
+ * the abuse of ->thread.sp because it's a dead variable
+ * while the thread is running on the CPU anyway; the true
+ * value is in the actual %rsp register.
+ */
+ current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack);
early_gdt_descr.address =
(unsigned long)get_cpu_gdt_rw(smp_processor_id());
initial_gs = per_cpu_offset(smp_processor_id());
+ smpboot_control = smp_processor_id();
#endif
initial_code = (unsigned long)wakeup_long64;
- saved_magic = 0x123456789abcdef0L;
+ saved_magic = 0x123456789abcdef0L;
#endif /* CONFIG_64BIT */
/*
OFFSET(TSS_sp1, tss_struct, x86_tss.sp1);
OFFSET(TSS_sp2, tss_struct, x86_tss.sp2);
OFFSET(X86_top_of_stack, pcpu_hot, top_of_stack);
+ OFFSET(X86_current_task, pcpu_hot, current_task);
#ifdef CONFIG_CALL_DEPTH_TRACKING
OFFSET(X86_call_depth, pcpu_hot, call_depth);
#endif
* tables and then reload them.
*/
- /* Set up the stack for verify_cpu(), similar to initial_stack below */
- leaq (__end_init_task - FRAME_SIZE)(%rip), %rsp
+ /* Set up the stack for verify_cpu() */
+ leaq (__end_init_task - PTREGS_SIZE)(%rip), %rsp
leaq _text(%rip), %rdi
UNWIND_HINT_EMPTY
ANNOTATE_NOENDBR // above
+#ifdef CONFIG_SMP
+ movl smpboot_control(%rip), %ecx
+
+ /* Get the per cpu offset for the given CPU# which is in ECX */
+ movq __per_cpu_offset(,%rcx,8), %rdx
+#else
+ xorl %edx, %edx /* zero-extended to clear all of RDX */
+#endif /* CONFIG_SMP */
+
+ /*
+ * Setup a boot time stack - Any secondary CPU will have lost its stack
+ * by now because the cr3-switch above unmaps the real-mode stack.
+ *
+ * RDX contains the per-cpu offset
+ */
+ movq pcpu_hot + X86_current_task(%rdx), %rax
+ movq TASK_threadsp(%rax), %rsp
+
/*
* We must switch to a new descriptor in kernel space for the GDT
* because soon the kernel won't have access anymore to the userspace
movl initial_gs+4(%rip),%edx
wrmsr
- /*
- * Setup a boot time stack - Any secondary CPU will have lost its stack
- * by now because the cr3-switch above unmaps the real-mode stack
- */
- movq initial_stack(%rip), %rsp
-
/* Setup and Load IDT */
pushq %rsi
call early_setup_idt
SYM_CODE_START(start_cpu0)
ANNOTATE_NOENDBR
UNWIND_HINT_EMPTY
- movq initial_stack(%rip), %rsp
+
+ /* Find the idle task stack */
+ movq PER_CPU_VAR(pcpu_hot) + X86_current_task, %rcx
+ movq TASK_threadsp(%rcx), %rsp
+
jmp .Ljump_to_C_code
SYM_CODE_END(start_cpu0)
#endif
#ifdef CONFIG_AMD_MEM_ENCRYPT
SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb)
#endif
-
-/*
- * The FRAME_SIZE gap is a convention which helps the in-kernel unwinder
- * reliably detect the end of the stack.
- */
-SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - FRAME_SIZE)
__FINITDATA
__INIT
SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page))
.align 16
+SYM_DATA(smpboot_control, .long 0)
+
+ .align 16
/* This must match the first entry in level2_kernel_pgt */
SYM_DATA(phys_base, .quad 0x0)
EXPORT_SYMBOL(phys_base)
idle->thread.sp = (unsigned long)task_pt_regs(idle);
early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu);
initial_code = (unsigned long)start_secondary;
- initial_stack = idle->thread.sp;
+
+ if (IS_ENABLED(CONFIG_X86_32)) {
+ initial_stack = idle->thread.sp;
+ } else {
+ smpboot_control = cpu;
+ }
/* Enable the espfix hack for this CPU */
init_espfix_ap(cpu);
ANNOTATE_NOENDBR
cld
- mov initial_stack(%rip), %rsp
+ leaq (__end_init_task - PTREGS_SIZE)(%rip), %rsp
/* Set up %gs.
*
projects / platform / kernel / linux-starfive.git / commitdiff