[PATCH v3 25/59] x86/percpu: Move current_top_of_stack next to current_task

Peter Zijlstra
2022-09-15T11:43:56Z

From: Thomas Gleixner <tglx@linutronix.de>

Extend the struct pcpu_hot cacheline with current_top_of_stack;
another very frequently used value.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/entry/entry_32.S | 4 ++--
arch/x86/entry/entry_64.S | 6 +++---
arch/x86/entry/entry_64_compat.S | 6 +++---
arch/x86/include/asm/current.h | 1 +
arch/x86/include/asm/processor.h | 4 +---
arch/x86/kernel/asm-offsets.c | 2 ++
arch/x86/kernel/cpu/common.c | 12 +-----------
arch/x86/kernel/process_32.c | 4 ++--
arch/x86/kernel/process_64.c | 2 +-
arch/x86/kernel/smpboot.c | 2 +-
arch/x86/kernel/traps.c | 4 ++--
11 files changed, 19 insertions(+), 28 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1181,7 +1181,7 @@ SYM_CODE_START(asm_exc_nmi)
* is using the thread stack right now, so it's safe for us to use it.
*/
movl %esp, %ebx
- movl PER_CPU_VAR(cpu_current_top_of_stack), %esp
+ movl PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %esp
call exc_nmi
movl %ebx, %esp

@@ -1243,7 +1243,7 @@ SYM_CODE_START(rewind_stack_and_make_dea
/* Prevent any naive code from trying to unwind to our caller. */
xorl %ebp, %ebp

- movl PER_CPU_VAR(cpu_current_top_of_stack), %esi
+ movl PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %esi
leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp

call make_task_dead
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -92,7 +92,7 @@ SYM_CODE_START(entry_SYSCALL_64)
/* tss.sp2 is scratch space. */
movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp
- movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp

SYM_INNER_LABEL(entry_SYSCALL_64_safe_stack, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
@@ -1209,7 +1209,7 @@ SYM_CODE_START(asm_exc_nmi)
FENCE_SWAPGS_USER_ENTRY
SWITCH_TO_KERNEL_CR3 scratch_reg=%rdx
movq %rsp, %rdx
- movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp
UNWIND_HINT_IRET_REGS base=%rdx offset=8
pushq 5*8(%rdx) /* pt_regs->ss */
pushq 4*8(%rdx) /* pt_regs->rsp */
@@ -1525,7 +1525,7 @@ SYM_CODE_START_NOALIGN(rewind_stack_and_
/* Prevent any naive code from trying to unwind to our caller. */
xorl %ebp, %ebp

- movq PER_CPU_VAR(cpu_current_top_of_stack), %rax
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rax
leaq -PTREGS_SIZE(%rax), %rsp
UNWIND_HINT_REGS

--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -58,7 +58,7 @@ SYM_CODE_START(entry_SYSENTER_compat)
SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
popq %rax

- movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp

/* Construct struct pt_regs on stack */
pushq $__USER32_DS /* pt_regs->ss */
@@ -191,7 +191,7 @@ SYM_CODE_START(entry_SYSCALL_compat)
SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp

/* Switch to the kernel stack */
- movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp

SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
@@ -332,7 +332,7 @@ SYM_CODE_START(entry_INT80_compat)
ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV

movq %rsp, %rax
- movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+ movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp

pushq 5*8(%rax) /* regs->ss */
pushq 4*8(%rax) /* regs->rsp */
--- a/arch/x86/include/asm/current.h
+++ b/arch/x86/include/asm/current.h
@@ -17,6 +17,7 @@ struct pcpu_hot {
struct task_struct *current_task;
int preempt_count;
int cpu_number;
+ unsigned long top_of_stack;
};
u8 pad[64];
};
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -426,8 +426,6 @@ struct irq_stack {
char stack[IRQ_STACK_SIZE];
} __aligned(IRQ_STACK_SIZE);

-DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack);
-
#ifdef CONFIG_X86_64
struct fixed_percpu_data {
/*
@@ -566,7 +564,7 @@ static __always_inline unsigned long cur
* and around vm86 mode and sp0 on x86_64 is special because of the
* entry trampoline.
*/
- return this_cpu_read_stable(cpu_current_top_of_stack);
+ return this_cpu_read_stable(pcpu_hot.top_of_stack);
}

static __always_inline bool on_thread_stack(void)
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -109,6 +109,8 @@ static void __used common(void)
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);
+
if (IS_ENABLED(CONFIG_KVM_INTEL)) {
BLANK();
OFFSET(VMX_spec_ctrl, vcpu_vmx, spec_ctrl);
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2003,6 +2003,7 @@ static __init int setup_clearcpuid(char
DEFINE_PER_CPU_ALIGNED(struct pcpu_hot, pcpu_hot) = {
.current_task = &init_task,
.preempt_count = INIT_PREEMPT_COUNT,
+ .top_of_stack = TOP_OF_INIT_STACK,
};
EXPORT_PER_CPU_SYMBOL(pcpu_hot);

@@ -2014,8 +2015,6 @@ EXPORT_PER_CPU_SYMBOL_GPL(fixed_percpu_d
DEFINE_PER_CPU(void *, hardirq_stack_ptr);
DEFINE_PER_CPU(bool, hardirq_stack_inuse);

-DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) = TOP_OF_INIT_STACK;
-
static void wrmsrl_cstar(unsigned long val)
{
/*
@@ -2066,15 +2065,6 @@ void syscall_init(void)

#else /* CONFIG_X86_64 */

-/*
- * On x86_32, vm86 modifies tss.sp0, so sp0 isn't a reliable way to find
- * the top of the kernel stack. Use an extra percpu variable to track the
- * top of the kernel stack directly.
- */
-DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) =
- (unsigned long)&init_thread_union + THREAD_SIZE;
-EXPORT_PER_CPU_SYMBOL(cpu_current_top_of_stack);
-
#ifdef CONFIG_STACKPROTECTOR
DEFINE_PER_CPU(unsigned long, __stack_chk_guard);
EXPORT_PER_CPU_SYMBOL(__stack_chk_guard);
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -191,13 +191,13 @@ EXPORT_SYMBOL_GPL(start_thread);
arch_end_context_switch(next_p);

/*
- * Reload esp0 and cpu_current_top_of_stack. This changes
+ * Reload esp0 and pcpu_hot.top_of_stack. This changes
* current_thread_info(). Refresh the SYSENTER configuration in
* case prev or next is vm86.
*/
update_task_stack(next_p);
refresh_sysenter_cs(next);
- this_cpu_write(cpu_current_top_of_stack,
+ this_cpu_write(pcpu_hot.top_of_stack,
(unsigned long)task_stack_page(next_p) +
THREAD_SIZE);

--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -617,7 +617,7 @@ void compat_start_thread(struct pt_regs
* Switch the PDA and FPU contexts.
*/
raw_cpu_write(pcpu_hot.current_task, next_p);
- this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p));
+ raw_cpu_write(pcpu_hot.top_of_stack, task_top_of_stack(next_p));

switch_fpu_finish();

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1056,7 +1056,7 @@ int common_cpu_up(unsigned int cpu, stru

#ifdef CONFIG_X86_32
/* Stack for startup_32 can be just as for start_secondary onwards */
- per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
+ per_cpu(pcpu_hot.top_of_stack, cpu) = task_top_of_stack(idle);
#else
initial_gs = per_cpu_offset(cpu);
#endif
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -849,7 +849,7 @@ DEFINE_IDTENTRY_RAW(exc_int3)
*/
asmlinkage __visible noinstr struct pt_regs *sync_regs(struct pt_regs *eregs)
{
- struct pt_regs *regs = (struct pt_regs *)this_cpu_read(cpu_current_top_of_stack) - 1;
+ struct pt_regs *regs = (struct pt_regs *)this_cpu_read(pcpu_hot.top_of_stack) - 1;
if (regs != eregs)
*regs = *eregs;
return regs;
@@ -867,7 +867,7 @@ asmlinkage __visible noinstr struct pt_r
* trust it and switch to the current kernel stack
*/
if (ip_within_syscall_gap(regs)) {
- sp = this_cpu_read(cpu_current_top_of_stack);
+ sp = this_cpu_read(pcpu_hot.top_of_stack);
goto sync;
}