Commit 3d8c1a01 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
Browse files

arm64: smp: initialize cpu offset earlier 



Now that we have a consistent place to initialize CPU context registers
early in the boot path, let's also initialize the per-cpu offset here.
This makes the primary and secondary boot paths more consistent, and
allows for the use of per-cpu operations earlier, which will be
necessary for instrumentation with KCSAN.

Note that smp_prepare_boot_cpu() still needs to re-initialize CPU0's
offset as immediately prior to this the per-cpu areas may be
reallocated, and hence the boot-time offset may be stale. A comment is
added to make this clear.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210520115031.18509-7-mark.rutland@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 8e334d72

arch/arm64/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
int main(void)

{

  DEFINE(TSK_ACTIVE_MM,		offsetof(struct task_struct, active_mm));

  DEFINE(TSK_CPU,		offsetof(struct task_struct, cpu));

  BLANK();

  DEFINE(TSK_TI_FLAGS,		offsetof(struct task_struct, thread_info.flags));

  DEFINE(TSK_TI_PREEMPT,	offsetof(struct task_struct, thread_info.preempt_count));

arch/arm64/kernel/head.S

+11 −6
Original line number Diff line number Diff line
@@ -402,17 +402,22 @@ SYM_FUNC_END(__create_page_tables) 
	 * its location in the task stack. We reserve the entire pt_regs space

	 * for consistency with user tasks and kthreads.

	 */

	.macro	init_cpu_task tsk, tmp

	.macro	init_cpu_task tsk, tmp1, tmp2

	msr	sp_el0, \tsk



	ldr	\tmp, [\tsk, #TSK_STACK]

	add	sp, \tmp, #THREAD_SIZE

	ldr	\tmp1, [\tsk, #TSK_STACK]

	add	sp, \tmp1, #THREAD_SIZE

	sub	sp, sp, #PT_REGS_SIZE



	stp	xzr, xzr, [sp, #S_STACKFRAME]

	add	x29, sp, #S_STACKFRAME



	scs_load \tsk, \tmp

	scs_load \tsk, \tmp1



	adr_l	\tmp1, __per_cpu_offset

	ldr	w\tmp2, [\tsk, #TSK_CPU]

	ldr	\tmp1, [\tmp1, \tmp2, lsl #3]

	set_this_cpu_offset \tmp1

	.endm



/*
@@ -422,7 +427,7 @@ SYM_FUNC_END(__create_page_tables) 
 */

SYM_FUNC_START_LOCAL(__primary_switched)

	adr_l	x4, init_task

	init_cpu_task x4, x5

	init_cpu_task x4, x5, x6



	adr_l	x8, vectors			// load VBAR_EL1 with virtual

	msr	vbar_el1, x8			// vector table address
@@ -650,7 +655,7 @@ SYM_FUNC_START_LOCAL(__secondary_switched) 
	ldr	x2, [x0, #CPU_BOOT_TASK]

	cbz	x2, __secondary_too_slow



	init_cpu_task x2, x1

	init_cpu_task x2, x1, x3



#ifdef CONFIG_ARM64_PTR_AUTH

	ptrauth_keys_init_cpu x2, x3, x4, x5

arch/arm64/kernel/setup.c

+0 −6
Original line number Diff line number Diff line
@@ -87,12 +87,6 @@ void __init smp_setup_processor_id(void) 
	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;

	set_cpu_logical_map(0, mpidr);



	/*

	 * clear __my_cpu_offset on boot CPU to avoid hang caused by

	 * using percpu variable early, for example, lockdep will

	 * access percpu variable inside lock_release

	 */

	set_my_cpu_offset(0);

	pr_info("Booting Linux on physical CPU 0x%010lx [0x%08x]\n",

		(unsigned long)mpidr, read_cpuid_id());

}

arch/arm64/kernel/smp.c

+6 −4
Original line number Diff line number Diff line
@@ -198,10 +198,7 @@ asmlinkage notrace void secondary_start_kernel(void) 
	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;

	struct mm_struct *mm = &init_mm;

	const struct cpu_operations *ops;

	unsigned int cpu;



	cpu = task_cpu(current);

	set_my_cpu_offset(per_cpu_offset(cpu));

	unsigned int cpu = smp_processor_id();



	/*

	 * All kernel threads share the same mm context; grab a
@@ -448,6 +445,11 @@ void __init smp_cpus_done(unsigned int max_cpus) 


void __init smp_prepare_boot_cpu(void)

{

	/*

	 * The runtime per-cpu areas have been allocated by

	 * setup_per_cpu_areas(), and CPU0's boot time per-cpu area will be

	 * freed shortly, so we must move over to the runtime per-cpu area.

	 */

	set_my_cpu_offset(per_cpu_offset(smp_processor_id()));

	cpuinfo_store_boot_cpu();