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author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-08-22 13:06:21 +0300 |
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committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-08-29 12:05:01 +0300 |
commit | 7f79695cc1b6aa6d80a861780d9f8ce75d3dddcb (patch) | |
tree | dd34f15ed90df7e9920e29b753aa2ff0cf6feff3 /arch/s390/include/asm/lowcore.h | |
parent | 0eab11c7e0d30de14a15ccd8269eef238321a8e1 (diff) | |
download | linux-7f79695cc1b6aa6d80a861780d9f8ce75d3dddcb.tar.xz |
s390/fpu: improve kernel_fpu_[begin|end]
In case of nested user of the FPU or vector registers in the kernel
the current code uses the mask of the FPU/vector registers of the
previous contexts to decide which registers to save and restore.
E.g. if the previous context used KERNEL_VXR_V0V7 and the next
context wants to use KERNEL_VXR_V24V31 the first 8 vector registers
are stored to the FPU state structure. But this is not necessary
as the next context does not use these registers.
Rework the FPU/vector register save and restore code. The new code
does a few things differently:
1) A lowcore field is used instead of a per-cpu variable.
2) The kernel_fpu_end function now has two parameters just like
kernel_fpu_begin. The register flags are required by both
functions to save / restore the minimal register set.
3) The inline functions kernel_fpu_begin/kernel_fpu_end now do the
update of the register masks. If the user space FPU registers
have already been stored neither save_fpu_regs nor the
__kernel_fpu_begin/__kernel_fpu_end functions have to be called
for the first context. In this case kernel_fpu_begin adds 7
instructions and kernel_fpu_end adds 4 instructions.
3) The inline assemblies in __kernel_fpu_begin / __kernel_fpu_end
to save / restore the vector registers are simplified a bit.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include/asm/lowcore.h')
-rw-r--r-- | arch/s390/include/asm/lowcore.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h index d79ba7cf75b0..7b93b78f423c 100644 --- a/arch/s390/include/asm/lowcore.h +++ b/arch/s390/include/asm/lowcore.h @@ -129,7 +129,8 @@ struct lowcore { __u8 pad_0x0390[0x0398-0x0390]; /* 0x0390 */ __u64 gmap; /* 0x0398 */ __u32 spinlock_lockval; /* 0x03a0 */ - __u8 pad_0x03a0[0x0400-0x03a4]; /* 0x03a4 */ + __u32 fpu_flags; /* 0x03a4 */ + __u8 pad_0x03a8[0x0400-0x03a8]; /* 0x03a8 */ /* Per cpu primary space access list */ __u32 paste[16]; /* 0x0400 */ |