linux/arch/x86/kernel
Linus Torvalds 34ddc81a23 i387: re-introduce FPU state preloading at context switch time
After all the FPU state cleanups and finally finding the problem that
caused all our FPU save/restore problems, this re-introduces the
preloading of FPU state that was removed in commit b3b0870ef3 ("i387:
do not preload FPU state at task switch time").

However, instead of simply reverting the removal, this reimplements
preloading with several fixes, most notably

 - properly abstracted as a true FPU state switch, rather than as
   open-coded save and restore with various hacks.

   In particular, implementing it as a proper FPU state switch allows us
   to optimize the CR0.TS flag accesses: there is no reason to set the
   TS bit only to then almost immediately clear it again.  CR0 accesses
   are quite slow and expensive, don't flip the bit back and forth for
   no good reason.

 - Make sure that the same model works for both x86-32 and x86-64, so
   that there are no gratuitous differences between the two due to the
   way they save and restore segment state differently due to
   architectural differences that really don't matter to the FPU state.

 - Avoid exposing the "preload" state to the context switch routines,
   and in particular allow the concept of lazy state restore: if nothing
   else has used the FPU in the meantime, and the process is still on
   the same CPU, we can avoid restoring state from memory entirely, just
   re-expose the state that is still in the FPU unit.

   That optimized lazy restore isn't actually implemented here, but the
   infrastructure is set up for it.  Of course, older CPU's that use
   'fnsave' to save the state cannot take advantage of this, since the
   state saving also trashes the state.

In other words, there is now an actual _design_ to the FPU state saving,
rather than just random historical baggage.  Hopefully it's easier to
follow as a result.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-18 14:03:48 -08:00
..
acpi x86, acpi: Skip acpi x2apic entries if the x2apic feature is not present 2011-12-23 11:00:50 -08:00
apic x86, UV: Update Boot messages for SGI UV2 platform 2012-01-08 12:35:44 +01:00
cpu perf: Fix double start/stop in x86_pmu_start() 2012-02-07 16:58:56 +01:00
.gitignore
alternative.c
amd_gart_64.c
amd_nb.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
apb_timer.c
aperture_64.c
apm_32.c module_param: make bool parameters really bool (arch) 2012-01-13 09:32:18 +10:30
asm-offsets.c
asm-offsets_32.c
asm-offsets_64.c
audit_64.c
bootflag.c
check.c
cpuid.c switch device_get_devnode() and ->devnode() to umode_t * 2012-01-03 22:54:55 -05:00
crash.c
crash_dump_32.c
crash_dump_64.c
devicetree.c
doublefault_32.c
dumpstack.c bugs, x86: Fix printk levels for panic, softlockups and stack dumps 2012-01-26 21:28:45 +01:00
dumpstack_32.c
dumpstack_64.c Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus', 'sched-urgent-for-linus' and 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-02-02 11:11:13 -08:00
e820.c Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2012-01-18 15:51:48 -08:00
early-quirks.c
early_printk.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:13:40 -08:00
entry_32.S Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit 2012-01-17 16:41:31 -08:00
entry_64.S Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit 2012-01-17 16:41:31 -08:00
ftrace.c
head.c
head32.c
head64.c
head_32.S
head_64.S
hpet.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core 2012-01-07 12:03:30 -08:00
hw_breakpoint.c
i386_ksyms_32.c
i387.c
i8237.c
i8253.c
i8259.c
init_task.c
io_delay.c
ioport.c
irq.c Merge branch 'x86-apic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 13:58:21 -08:00
irq_32.c
irq_64.c
irq_work.c
irqinit.c
jump_label.c
kdebugfs.c
kgdb.c
kprobes.c
kvm.c KVM guest: remove KVM guest pv mmu support 2011-12-27 11:17:08 +02:00
kvmclock.c
ldt.c
machine_kexec_32.c
machine_kexec_64.c
Makefile Merge branch 'x86-syscall-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-16 18:19:19 -08:00
mca_32.c
microcode_amd.c x86/microcode_amd: Add support for CPU family specific container files 2012-01-26 12:06:39 +01:00
microcode_core.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core 2012-01-07 12:03:30 -08:00
microcode_intel.c
mmconf-fam10h_64.c
module.c
mpparse.c
msr.c switch device_get_devnode() and ->devnode() to umode_t * 2012-01-03 22:54:55 -05:00
nmi.c
nmi_selftest.c
paravirt-spinlocks.c
paravirt.c
paravirt_patch_32.c
paravirt_patch_64.c
pci-calgary_64.c
pci-dma.c
pci-iommu_table.c
pci-nommu.c
pci-swiotlb.c
pcspeaker.c
probe_roms.c
process.c
process_32.c i387: re-introduce FPU state preloading at context switch time 2012-02-18 14:03:48 -08:00
process_64.c i387: re-introduce FPU state preloading at context switch time 2012-02-18 14:03:48 -08:00
ptrace.c audit: inline audit_syscall_entry to reduce burden on archs 2012-01-17 16:16:56 -05:00
pvclock.c
quirks.c
reboot.c x86/reboot: Remove VersaLogic Menlow reboot quirk 2012-01-30 10:52:33 +01:00
reboot_32.S
reboot_fixups_32.c
relocate_kernel_32.S
relocate_kernel_64.S
resource.c
rtc.c
setup.c Merge branch 'x86-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:12:33 -08:00
setup_percpu.c
signal.c signal: add block_sigmask() for adding sigmask to current->blocked 2012-01-10 16:30:54 -08:00
smp.c x86, reboot: Fix typo in nmi reboot path 2012-01-07 12:19:37 +01:00
smpboot.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:13:40 -08:00
stacktrace.c
step.c
sys_i386_32.c
sys_x86_64.c
syscall_32.c
syscall_64.c
tboot.c
tce_64.c
test_nx.c
test_rodata.c
time.c
tls.c
tls.h
topology.c
trampoline.c
trampoline_32.S
trampoline_64.S
traps.c i387: re-introduce FPU state preloading at context switch time 2012-02-18 14:03:48 -08:00
tsc.c Merge remote-tracking branch 'linus/master' into x86/urgent 2012-01-19 12:56:50 -08:00
tsc_sync.c
verify_cpu.S
vm86_32.c x86-32: Fix build failure with AUDIT=y, AUDITSYSCALL=n 2012-01-17 18:10:11 -08:00
vmlinux.lds.S
vsmp_64.c
vsyscall_64.c
vsyscall_emu_64.S
vsyscall_trace.h
x86_init.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
x8664_ksyms_64.c
xsave.c i387: move TS_USEDFPU flag from thread_info to task_struct 2012-02-18 10:19:41 -08:00