x86, fpu: split FPU state from task struct - v5
Split the FPU save area from the task struct. This allows easy migration
of FPU context, and it's generally cleaner. It also allows the following
two optimizations:
1) only allocate when the application actually uses FPU, so in the first
lazy FPU trap. This could save memory for non-fpu using apps. Next patch
does this lazy allocation.
2) allocate the right size for the actual cpu rather than 512 bytes always.
Patches enabling xsave/xrstor support (coming shortly) will take advantage
of this.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index c3920ea..7a2a2e9 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -29,6 +29,7 @@
obj-y += tsc_$(BITS).o io_delay.o rtc.o
obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o
+obj-y += process.o
obj-y += i387.o
obj-y += ptrace.o
obj-y += ds.o
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 8f8102d..baf632b 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/regset.h>
#include <linux/sched.h>
+#include <linux/bootmem.h>
#include <asm/sigcontext.h>
#include <asm/processor.h>
@@ -35,17 +36,18 @@
#endif
static unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
+unsigned int xstate_size;
+static struct i387_fxsave_struct fx_scratch __cpuinitdata;
-void mxcsr_feature_mask_init(void)
+void __cpuinit mxcsr_feature_mask_init(void)
{
unsigned long mask = 0;
clts();
if (cpu_has_fxsr) {
- memset(¤t->thread.i387.fxsave, 0,
- sizeof(struct i387_fxsave_struct));
- asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
- mask = current->thread.i387.fxsave.mxcsr_mask;
+ memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
+ asm volatile("fxsave %0" : : "m" (fx_scratch));
+ mask = fx_scratch.mxcsr_mask;
if (mask == 0)
mask = 0x0000ffbf;
}
@@ -53,6 +55,17 @@
stts();
}
+void __init init_thread_xstate(void)
+{
+ if (cpu_has_fxsr)
+ xstate_size = sizeof(struct i387_fxsave_struct);
+#ifdef CONFIG_X86_32
+ else
+ xstate_size = sizeof(struct i387_fsave_struct);
+#endif
+ init_task.thread.xstate = alloc_bootmem(xstate_size);
+}
+
#ifdef CONFIG_X86_64
/*
* Called at bootup to set up the initial FPU state that is later cloned
@@ -61,10 +74,6 @@
void __cpuinit fpu_init(void)
{
unsigned long oldcr0 = read_cr0();
- extern void __bad_fxsave_alignment(void);
-
- if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
- __bad_fxsave_alignment();
set_in_cr4(X86_CR4_OSFXSR);
set_in_cr4(X86_CR4_OSXMMEXCPT);
@@ -93,18 +102,19 @@
}
if (cpu_has_fxsr) {
- memset(&tsk->thread.i387.fxsave, 0,
- sizeof(struct i387_fxsave_struct));
- tsk->thread.i387.fxsave.cwd = 0x37f;
+ struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
+
+ memset(fx, 0, xstate_size);
+ fx->cwd = 0x37f;
if (cpu_has_xmm)
- tsk->thread.i387.fxsave.mxcsr = MXCSR_DEFAULT;
+ fx->mxcsr = MXCSR_DEFAULT;
} else {
- memset(&tsk->thread.i387.fsave, 0,
- sizeof(struct i387_fsave_struct));
- tsk->thread.i387.fsave.cwd = 0xffff037fu;
- tsk->thread.i387.fsave.swd = 0xffff0000u;
- tsk->thread.i387.fsave.twd = 0xffffffffu;
- tsk->thread.i387.fsave.fos = 0xffff0000u;
+ struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
+ memset(fp, 0, xstate_size);
+ fp->cwd = 0xffff037fu;
+ fp->swd = 0xffff0000u;
+ fp->twd = 0xffffffffu;
+ fp->fos = 0xffff0000u;
}
/*
* Only the device not available exception or ptrace can call init_fpu.
@@ -132,7 +142,7 @@
init_fpu(target);
return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
- &target->thread.i387.fxsave, 0, -1);
+ &target->thread.xstate->fxsave, 0, -1);
}
int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
@@ -148,12 +158,12 @@
set_stopped_child_used_math(target);
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
- &target->thread.i387.fxsave, 0, -1);
+ &target->thread.xstate->fxsave, 0, -1);
/*
* mxcsr reserved bits must be masked to zero for security reasons.
*/
- target->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
+ target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
return ret;
}
@@ -233,7 +243,7 @@
static void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
- struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
+ struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
int i;
@@ -273,7 +283,7 @@
const struct user_i387_ia32_struct *env)
{
- struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
+ struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
int i;
@@ -310,7 +320,8 @@
if (!cpu_has_fxsr) {
return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
- &target->thread.i387.fsave, 0, -1);
+ &target->thread.xstate->fsave, 0,
+ -1);
}
if (kbuf && pos == 0 && count == sizeof(env)) {
@@ -338,7 +349,7 @@
if (!cpu_has_fxsr) {
return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
- &target->thread.i387.fsave, 0, -1);
+ &target->thread.xstate->fsave, 0, -1);
}
if (pos > 0 || count < sizeof(env))
@@ -358,11 +369,11 @@
static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
{
struct task_struct *tsk = current;
+ struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
unlazy_fpu(tsk);
- tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
- if (__copy_to_user(buf, &tsk->thread.i387.fsave,
- sizeof(struct i387_fsave_struct)))
+ fp->status = fp->swd;
+ if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
return -1;
return 1;
}
@@ -370,6 +381,7 @@
static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
{
struct task_struct *tsk = current;
+ struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
struct user_i387_ia32_struct env;
int err = 0;
@@ -379,12 +391,12 @@
if (__copy_to_user(buf, &env, sizeof(env)))
return -1;
- err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
+ err |= __put_user(fx->swd, &buf->status);
err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
if (err)
return -1;
- if (__copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
+ if (__copy_to_user(&buf->_fxsr_env[0], fx,
sizeof(struct i387_fxsave_struct)))
return -1;
return 1;
@@ -417,7 +429,7 @@
struct task_struct *tsk = current;
clear_fpu(tsk);
- return __copy_from_user(&tsk->thread.i387.fsave, buf,
+ return __copy_from_user(&tsk->thread.xstate->fsave, buf,
sizeof(struct i387_fsave_struct));
}
@@ -428,10 +440,10 @@
int err;
clear_fpu(tsk);
- err = __copy_from_user(&tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
+ err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
sizeof(struct i387_fxsave_struct));
/* mxcsr reserved bits must be masked to zero for security reasons */
- tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
+ tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
if (err || __copy_from_user(&env, buf, sizeof(env)))
return 1;
convert_to_fxsr(tsk, &env);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
new file mode 100644
index 0000000..ead24ef
--- /dev/null
+++ b/arch/x86/kernel/process.c
@@ -0,0 +1,35 @@
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+
+static struct kmem_cache *task_xstate_cachep;
+
+int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
+{
+ *dst = *src;
+ dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
+ if (!dst->thread.xstate)
+ return -ENOMEM;
+ WARN_ON((unsigned long)dst->thread.xstate & 15);
+ memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
+ return 0;
+}
+
+void free_thread_info(struct thread_info *ti)
+{
+ kmem_cache_free(task_xstate_cachep, ti->task->thread.xstate);
+ ti->task->thread.xstate = NULL;
+
+ free_pages((unsigned long)(ti), get_order(THREAD_SIZE));
+}
+
+void arch_task_cache_init(void)
+{
+ task_xstate_cachep =
+ kmem_cache_create("task_xstate", xstate_size,
+ __alignof__(union thread_xstate),
+ SLAB_PANIC, NULL);
+}
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index a3790a3..3890a5d 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -703,7 +703,7 @@
/* we're going to use this soon, after a few expensive things */
if (next_p->fpu_counter > 5)
- prefetch(&next->i387.fxsave);
+ prefetch(next->xstate);
/*
* Reload esp0.
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4c13b14..b795e83 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -682,7 +682,7 @@
/* we're going to use this soon, after a few expensive things */
if (next_p->fpu_counter>5)
- prefetch(&next->i387.fxsave);
+ prefetch(next->xstate);
/*
* Reload esp0, LDT and the page table pointer:
diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index dc42730..8d136a7 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -1208,11 +1208,6 @@
#endif
set_trap_gate(19, &simd_coprocessor_error);
- /*
- * Verify that the FXSAVE/FXRSTOR data will be 16-byte aligned.
- * Generate a build-time error if the alignment is wrong.
- */
- BUILD_BUG_ON(offsetof(struct task_struct, thread.i387.fxsave) & 15);
if (cpu_has_fxsr) {
printk(KERN_INFO "Enabling fast FPU save and restore... ");
set_in_cr4(X86_CR4_OSFXSR);
@@ -1233,6 +1228,7 @@
set_bit(SYSCALL_VECTOR, used_vectors);
+ init_thread_xstate();
/*
* Should be a barrier for any external CPU state:
*/
diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index 6d883b1..dc0cb49 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -1128,7 +1128,7 @@
if (!used_math())
init_fpu(me);
- restore_fpu_checking(&me->thread.i387.fxsave);
+ restore_fpu_checking(&me->thread.xstate->fxsave);
task_thread_info(me)->status |= TS_USEDFPU;
me->fpu_counter++;
}
@@ -1164,6 +1164,10 @@
#endif
/*
+ * initialize the per thread extended state:
+ */
+ init_thread_xstate();
+ /*
* Should be a barrier for any external CPU state.
*/
cpu_init();