The struct fpu.initialized member is always set to one for user tasks
and zero for kernel tasks. This avoids saving/restoring the FPU
registers for kernel threads.
The ->initialized = 0 case for user tasks has been removed in previous
changes, for instance, by doing an explicit unconditional init at fork()
time for FPU-less systems which was otherwise delayed until the emulated
opcode.
The context switch code (switch_fpu_prepare() + switch_fpu_finish())
can't unconditionally save/restore registers for kernel threads. Not
only would it slow down the switch but also load a zeroed xcomp_bv for
XSAVES.
For kernel_fpu_begin() (+end) the situation is similar: EFI with runtime
services uses this before alternatives_patched is true. Which means that
this function is used too early and it wasn't the case before.
For those two cases, use current->mm to distinguish between user and
kernel thread. For kernel_fpu_begin() skip save/restore of the FPU
registers.
During the context switch into a kernel thread don't do anything. There
is no reason to save the FPU state of a kernel thread.
The reordering in __switch_to() is important because the current()
pointer needs to be valid before switch_fpu_finish() is invoked so ->mm
is seen of the new task instead the old one.
N.B.: fpu__save() doesn't need to check ->mm because it is called by
user tasks only.
[ bp: Massage. ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Babu Moger <Babu.Moger@amd.com>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Dmitry Safonov <dima@arista.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-8-bigeasy@linutronix.de
size_t frame_size,
void __user **fpstate)
{
- struct fpu *fpu = ¤t->thread.fpu;
- unsigned long sp;
+ unsigned long sp, fx_aligned, math_size;
/* Default to using normal stack */
sp = regs->sp;
ksig->ka.sa.sa_restorer)
sp = (unsigned long) ksig->ka.sa.sa_restorer;
- if (fpu->initialized) {
- unsigned long fx_aligned, math_size;
-
- sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
- *fpstate = (struct _fpstate_32 __user *) sp;
- if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
- math_size) < 0)
- return (void __user *) -1L;
- }
+ sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
+ *fpstate = (struct _fpstate_32 __user *) sp;
+ if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
+ math_size) < 0)
+ return (void __user *) -1L;
sp -= frame_size;
/* Align the stack pointer according to the i386 ABI,
*
* - switch_fpu_finish() restores the new state as
* necessary.
+ *
+ * The FPU context is only stored/restored for a user task and
+ * ->mm is used to distinguish between kernel and user threads.
*/
static inline void
switch_fpu_prepare(struct fpu *old_fpu, int cpu)
{
- if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) {
+ if (static_cpu_has(X86_FEATURE_FPU) && current->mm) {
if (!copy_fpregs_to_fpstate(old_fpu))
old_fpu->last_cpu = -1;
else
/* But leave fpu_fpregs_owner_ctx! */
trace_x86_fpu_regs_deactivated(old_fpu);
- } else
- old_fpu->last_cpu = -1;
+ }
}
/*
*/
static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
{
- bool preload = static_cpu_has(X86_FEATURE_FPU) &&
- new_fpu->initialized;
+ if (static_cpu_has(X86_FEATURE_FPU)) {
+ if (!fpregs_state_valid(new_fpu, cpu)) {
+ if (current->mm)
+ copy_kernel_to_fpregs(&new_fpu->state);
+ }
- if (preload) {
- if (!fpregs_state_valid(new_fpu, cpu))
- copy_kernel_to_fpregs(&new_fpu->state);
fpregs_activate(new_fpu);
}
}
*/
unsigned int last_cpu;
- /*
- * @initialized:
- *
- * This flag indicates whether this context is initialized: if the task
- * is not running then we can restore from this context, if the task
- * is running then we should save into this context.
- */
- unsigned char initialized;
-
/*
* @avx512_timestamp:
*
TP_STRUCT__entry(
__field(struct fpu *, fpu)
- __field(bool, initialized)
__field(u64, xfeatures)
__field(u64, xcomp_bv)
),
TP_fast_assign(
__entry->fpu = fpu;
- __entry->initialized = fpu->initialized;
if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
__entry->xfeatures = fpu->state.xsave.header.xfeatures;
__entry->xcomp_bv = fpu->state.xsave.header.xcomp_bv;
}
),
- TP_printk("x86/fpu: %p initialized: %d xfeatures: %llx xcomp_bv: %llx",
+ TP_printk("x86/fpu: %p xfeatures: %llx xcomp_bv: %llx",
__entry->fpu,
- __entry->initialized,
__entry->xfeatures,
__entry->xcomp_bv
)
kernel_fpu_disable();
- if (fpu->initialized) {
+ if (current->mm) {
/*
* Ignore return value -- we don't care if reg state
* is clobbered.
{
struct fpu *fpu = ¤t->thread.fpu;
- if (fpu->initialized)
+ if (current->mm)
copy_kernel_to_fpregs(&fpu->state);
kernel_fpu_enable();
preempt_disable();
trace_x86_fpu_before_save(fpu);
- if (fpu->initialized) {
- if (!copy_fpregs_to_fpstate(fpu)) {
- copy_kernel_to_fpregs(&fpu->state);
- }
- }
+
+ if (!copy_fpregs_to_fpstate(fpu))
+ copy_kernel_to_fpregs(&fpu->state);
+
trace_x86_fpu_after_save(fpu);
preempt_enable();
}
{
dst_fpu->last_cpu = -1;
- if (!src_fpu->initialized || !static_cpu_has(X86_FEATURE_FPU))
+ if (!static_cpu_has(X86_FEATURE_FPU))
return 0;
WARN_ON_FPU(src_fpu != ¤t->thread.fpu);
{
WARN_ON_FPU(fpu != ¤t->thread.fpu);
- if (!fpu->initialized) {
- fpstate_init(&fpu->state);
- trace_x86_fpu_init_state(fpu);
+ fpstate_init(&fpu->state);
+ trace_x86_fpu_init_state(fpu);
- trace_x86_fpu_activate_state(fpu);
- /* Safe to do for the current task: */
- fpu->initialized = 1;
- }
+ trace_x86_fpu_activate_state(fpu);
}
/*
*
* - or it's called for stopped tasks (ptrace), in which case the
* registers were already saved by the context-switch code when
- * the task scheduled out - we only have to initialize the registers
- * if they've never been initialized.
+ * the task scheduled out.
*
* If the task has used the FPU before then save it.
*/
void fpu__prepare_read(struct fpu *fpu)
{
- if (fpu == ¤t->thread.fpu) {
+ if (fpu == ¤t->thread.fpu)
fpu__save(fpu);
- } else {
- if (!fpu->initialized) {
- fpstate_init(&fpu->state);
- trace_x86_fpu_init_state(fpu);
-
- trace_x86_fpu_activate_state(fpu);
- /* Safe to do for current and for stopped child tasks: */
- fpu->initialized = 1;
- }
- }
}
/*
* This function must be called before we write a task's fpstate.
*
- * If the task has used the FPU before then invalidate any cached FPU registers.
- * If the task has not used the FPU before then initialize its fpstate.
+ * Invalidate any cached FPU registers.
*
* After this function call, after registers in the fpstate are
* modified and the child task has woken up, the child task will
*/
WARN_ON_FPU(fpu == ¤t->thread.fpu);
- if (fpu->initialized) {
- /* Invalidate any cached state: */
- __fpu_invalidate_fpregs_state(fpu);
- } else {
- fpstate_init(&fpu->state);
- trace_x86_fpu_init_state(fpu);
-
- trace_x86_fpu_activate_state(fpu);
- /* Safe to do for stopped child tasks: */
- fpu->initialized = 1;
- }
+ /* Invalidate any cached state: */
+ __fpu_invalidate_fpregs_state(fpu);
}
/*
preempt_disable();
if (fpu == ¤t->thread.fpu) {
- if (fpu->initialized) {
- /* Ignore delayed exceptions from user space */
- asm volatile("1: fwait\n"
- "2:\n"
- _ASM_EXTABLE(1b, 2b));
- fpregs_deactivate(fpu);
- }
+ /* Ignore delayed exceptions from user space */
+ asm volatile("1: fwait\n"
+ "2:\n"
+ _ASM_EXTABLE(1b, 2b));
+ fpregs_deactivate(fpu);
}
- fpu->initialized = 0;
-
trace_x86_fpu_dropped(fpu);
preempt_enable();
WARN_ON_FPU(!on_boot_cpu);
on_boot_cpu = 0;
-
- WARN_ON_FPU(current->thread.fpu.initialized);
}
/*
*/
int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
- struct fpu *target_fpu = &target->thread.fpu;
-
- return target_fpu->initialized ? regset->n : 0;
+ return regset->n;
}
int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
- struct fpu *target_fpu = &target->thread.fpu;
-
- if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->initialized)
+ if (boot_cpu_has(X86_FEATURE_FXSR))
return regset->n;
else
return 0;
int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
{
struct task_struct *tsk = current;
- struct fpu *fpu = &tsk->thread.fpu;
- int fpvalid;
-
- fpvalid = fpu->initialized;
- if (fpvalid)
- fpvalid = !fpregs_get(tsk, NULL,
- 0, sizeof(struct user_i387_ia32_struct),
- ufpu, NULL);
- return fpvalid;
+ return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct),
+ ufpu, NULL);
}
EXPORT_SYMBOL(dump_fpu);
{
struct fpu *fpu = ¤t->thread.fpu;
- if (!fpu->initialized)
- return NULL;
/*
* fpu__save() takes the CPU's xstate registers
* and saves them off to the 'fpu memory buffer.
if (prev->gs | next->gs)
lazy_load_gs(next->gs);
- switch_fpu_finish(next_fpu, cpu);
-
this_cpu_write(current_task, next_p);
+ switch_fpu_finish(next_fpu, cpu);
+
/* Load the Intel cache allocation PQR MSR. */
resctrl_sched_in();
x86_fsgsbase_load(prev, next);
- switch_fpu_finish(next_fpu, cpu);
-
/*
* Switch the PDA and FPU contexts.
*/
this_cpu_write(current_task, next_p);
this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p));
+ switch_fpu_finish(next_fpu, cpu);
+
/* Reload sp0. */
update_task_stack(next_p);
unsigned long sp = regs->sp;
unsigned long buf_fx = 0;
int onsigstack = on_sig_stack(sp);
- struct fpu *fpu = ¤t->thread.fpu;
+ int ret;
/* redzone */
if (IS_ENABLED(CONFIG_X86_64))
sp = (unsigned long) ka->sa.sa_restorer;
}
- if (fpu->initialized) {
- sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
- &buf_fx, &math_size);
- *fpstate = (void __user *)sp;
- }
+ sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
+ &buf_fx, &math_size);
+ *fpstate = (void __user *)sp;
sp = align_sigframe(sp - frame_size);
return (void __user *)-1L;
/* save i387 and extended state */
- if (fpu->initialized &&
- copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
+ ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
+ if (ret < 0)
return (void __user *)-1L;
return (void __user *)sp;
/*
* Ensure the signal handler starts with the new fpu state.
*/
- if (fpu->initialized)
- fpu__clear(fpu);
+ fpu__clear(fpu);
}
signal_setup_done(failed, ksig, stepping);
}
* dance to set PKRU if we do not need to. Check it
* first and assume that if the execute-only pkey is
* write-disabled that we do not have to set it
- * ourselves. We need preempt off so that nobody
- * can make fpregs inactive.
+ * ourselves.
*/
- preempt_disable();
if (!need_to_set_mm_pkey &&
- current->thread.fpu.initialized &&
!__pkru_allows_read(read_pkru(), execute_only_pkey)) {
- preempt_enable();
return execute_only_pkey;
}
- preempt_enable();
/*
* Set up PKRU so that it denies access for everything
projects / openwrt / staging / blogic.git / commitdiff