diff options
| author | Ingo Molnar <mingo@kernel.org> | 2025-04-10 00:11:23 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-04-14 09:18:29 +0300 |
| commit | 55bc30f2e34dcc17a370d1f6c1c992be107c4502 (patch) | |
| tree | 5c7102010a2b29b0bc2c9d83df4330abfbcf5bf6 | |
| parent | cb7ca40a3882360ce87191793449d48df0b29184 (diff) | |
| download | linux-55bc30f2e34dcc17a370d1f6c1c992be107c4502.tar.xz | |
x86/fpu: Remove the thread::fpu pointer
As suggested by Oleg, remove the thread::fpu pointer, as we can
calculate it via x86_task_fpu() at compile-time.
This improves code generation a bit:
kepler:~/tip> size vmlinux.before vmlinux.after
text data bss dec hex filename
26475405 10435342 1740804 38651551 24dc69f vmlinux.before
26475339 10959630 1216516 38651485 24dc65d vmlinux.after
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chang S. Bae <chang.seok.bae@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Uros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/r/20250409211127.3544993-5-mingo@kernel.org
| -rw-r--r-- | arch/x86/include/asm/processor.h | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/init.c | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/vmlinux.lds.S | 4 |
5 files changed, 6 insertions, 10 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 5ea7e5d2c4de..b7f7c9c83409 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -514,12 +514,9 @@ struct thread_struct { struct thread_shstk shstk; #endif - - /* Floating point and extended processor state */ - struct fpu *fpu; }; -#define x86_task_fpu(task) ((task)->thread.fpu) +#define x86_task_fpu(task) ((struct fpu *)((void *)(task) + sizeof(*(task)))) /* * X86 doesn't need any embedded-FPU-struct quirks: diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 853a738fdf2d..974b276ff0da 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -600,13 +600,11 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal, * This is safe because task_struct size is a multiple of cacheline size. */ struct fpu *src_fpu = x86_task_fpu(current); - struct fpu *dst_fpu = (void *)dst + sizeof(*dst); + struct fpu *dst_fpu = x86_task_fpu(dst); BUILD_BUG_ON(sizeof(*dst) % SMP_CACHE_BYTES != 0); BUG_ON(!src_fpu); - dst->thread.fpu = dst_fpu; - /* The new task's FPU state cannot be valid in the hardware. */ dst_fpu->last_cpu = -1; diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 848ea79886ba..da41a1d2c40f 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -76,7 +76,6 @@ static struct fpu x86_init_fpu __attribute__ ((aligned (64))) __read_mostly; static void __init fpu__init_system_early_generic(void) { fpstate_reset(&x86_init_fpu); - current->thread.fpu = &x86_init_fpu; set_thread_flag(TIF_NEED_FPU_LOAD); x86_init_fpu.last_cpu = -1; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 3ce4cce46f3f..88868a90459e 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -102,8 +102,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) #ifdef CONFIG_VM86 dst->thread.vm86 = NULL; #endif - /* Drop the copied pointer to current's fpstate */ - dst->thread.fpu = NULL; return 0; } diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index ccdc45e5b759..d9ca2d1754da 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -181,6 +181,10 @@ SECTIONS /* equivalent to task_pt_regs(&init_task) */ __top_init_kernel_stack = __end_init_stack - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE; + __x86_init_fpu_begin = .; + . = __x86_init_fpu_begin + 128*PAGE_SIZE; + __x86_init_fpu_end = .; + #ifdef CONFIG_X86_32 /* 32 bit has nosave before _edata */ NOSAVE_DATA |