| Message ID | 20181128222035.2996-12-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/29] x86/fpu: Use ULL for shift in xfeature_uncompacted_offset() | expand |
On Wed, Nov 28, 2018 at 11:20:17PM +0100, Sebastian Andrzej Siewior wrote: > fpu__clear() only initializes the `state' if the FPU is present. This > initialisation is also required for the FPU-less system and takes place > math_emulate(). Since fpu__initialize() only performs the initialization > if ->initialized is zero it does not matter that it is invoked each time > an opcode is emulated. It makes the removal of ->initialized easier if > the struct is also initialized in FPU-less case at the same time. > > Move fpu__initialize() before the FPU check so it is also performed in > FPU-less case. > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > arch/x86/include/asm/fpu/internal.h | 1 - > arch/x86/kernel/fpu/core.c | 5 ++--- > arch/x86/math-emu/fpu_entry.c | 3 --- > 3 files changed, 2 insertions(+), 7 deletions(-) ... > diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c > index 9e2ba7e667f61..a873da6b46d6b 100644 > --- a/arch/x86/math-emu/fpu_entry.c > +++ b/arch/x86/math-emu/fpu_entry.c > @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info) > unsigned long code_base = 0; > unsigned long code_limit = 0; /* Initialized to stop compiler warnings */ > struct desc_struct code_descriptor; > - struct fpu *fpu = ¤t->thread.fpu; > - > - fpu__initialize(fpu); Ok, you're removing it here but where is the FPU going to be initialized now in the FPU-less case? IOW, it is not clear to me where fpu__clear() get called for the FPU emulation case now...
On 2018-12-12 18:11:29 [+0100], Borislav Petkov wrote: > > diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c > > index 9e2ba7e667f61..a873da6b46d6b 100644 > > --- a/arch/x86/math-emu/fpu_entry.c > > +++ b/arch/x86/math-emu/fpu_entry.c > > @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info) > > unsigned long code_base = 0; > > unsigned long code_limit = 0; /* Initialized to stop compiler warnings */ > > struct desc_struct code_descriptor; > > - struct fpu *fpu = ¤t->thread.fpu; > > - > > - fpu__initialize(fpu); > > Ok, you're removing it here but where is the FPU going to be initialized > now in the FPU-less case? > > IOW, it is not clear to me where fpu__clear() get called for the FPU > emulation case now... During fork() fpu__initialize() is called for both (with and without FPU) systems. The difference is made in fpu__clear() where the init is avoided in the FPU-less case. With this hunk: --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -365,8 +364,8 @@ void fpu__clear(struct fpu *fpu) /* * Make sure fpstate is cleared and initialized. */ + fpu__initialize(fpu); if (static_cpu_has(X86_FEATURE_FPU)) { - fpu__initialize(fpu); user_fpu_begin(); copy_init_fpstate_to_fpregs(); } we have the initialization in both cases. The only "negative" thing might be that we now have a memset(, 0, 684) (fpstate_init_soft()) during fork which would be avoided in case the FPU-less system has a userland which is compiled with a soft-FPU toolchain. I would worry about it once someone complains (and I doubt someone complains even if we remove soft FPU support). Sebastian
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 415d43bdaaa76..1d0e043bfc447 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -24,7 +24,6 @@ /* * High level FPU state handling functions: */ -extern void fpu__initialize(struct fpu *fpu); extern void fpu__prepare_read(struct fpu *fpu); extern void fpu__prepare_write(struct fpu *fpu); extern void fpu__save(struct fpu *fpu); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 1940319268aef..e43296854e379 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -223,7 +223,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu) * Activate the current task's in-memory FPU context, * if it has not been used before: */ -void fpu__initialize(struct fpu *fpu) +static void fpu__initialize(struct fpu *fpu) { WARN_ON_FPU(fpu != ¤t->thread.fpu); @@ -236,7 +236,6 @@ void fpu__initialize(struct fpu *fpu) fpu->initialized = 1; } } -EXPORT_SYMBOL_GPL(fpu__initialize); /* * This function must be called before we read a task's fpstate. @@ -365,8 +364,8 @@ void fpu__clear(struct fpu *fpu) /* * Make sure fpstate is cleared and initialized. */ + fpu__initialize(fpu); if (static_cpu_has(X86_FEATURE_FPU)) { - fpu__initialize(fpu); user_fpu_begin(); copy_init_fpstate_to_fpregs(); } diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c index 9e2ba7e667f61..a873da6b46d6b 100644 --- a/arch/x86/math-emu/fpu_entry.c +++ b/arch/x86/math-emu/fpu_entry.c @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info) unsigned long code_base = 0; unsigned long code_limit = 0; /* Initialized to stop compiler warnings */ struct desc_struct code_descriptor; - struct fpu *fpu = ¤t->thread.fpu; - - fpu__initialize(fpu); #ifdef RE_ENTRANT_CHECKING if (emulating) {
fpu__clear() only initializes the `state' if the FPU is present. This initialisation is also required for the FPU-less system and takes place math_emulate(). Since fpu__initialize() only performs the initialization if ->initialized is zero it does not matter that it is invoked each time an opcode is emulated. It makes the removal of ->initialized easier if the struct is also initialized in FPU-less case at the same time. Move fpu__initialize() before the FPU check so it is also performed in FPU-less case. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- arch/x86/include/asm/fpu/internal.h | 1 - arch/x86/kernel/fpu/core.c | 5 ++--- arch/x86/math-emu/fpu_entry.c | 3 --- 3 files changed, 2 insertions(+), 7 deletions(-)