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authorHendrik Brueckner <brueckner@linux.vnet.ibm.com>2015-06-10 12:53:42 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-07-22 09:58:01 +0200
commit9977e886cbbc758b4b601a160b5825ba573b5ca8 (patch)
tree773658886481d9e4d47b18a0f93a05f260580a4f /arch/s390/include/asm/ctl_reg.h
parentbd550337f61b6f10dee8c60d0bd17ac02367b56d (diff)
s390/kernel: lazy restore fpu registers
Improve the save and restore behavior of FPU register contents to use the vector extension within the kernel. The kernel does not use floating-point or vector registers and, therefore, saving and restoring the FPU register contents are performed for handling signals or switching processes only. To prepare for using vector instructions and vector registers within the kernel, enhance the save behavior and implement a lazy restore at return to user space from a system call or interrupt. To implement the lazy restore, the save_fpu_regs() sets a CPU information flag, CIF_FPU, to indicate that the FPU registers must be restored. Saving and setting CIF_FPU is performed in an atomic fashion to be interrupt-safe. When the kernel wants to use the vector extension or wants to change the FPU register state for a task during signal handling, the save_fpu_regs() must be called first. The CIF_FPU flag is also set at process switch. At return to user space, the FPU state is restored. In particular, the FPU state includes the floating-point or vector register contents, as well as, vector-enablement and floating-point control. The FPU state restore and clearing CIF_FPU is also performed in an atomic fashion. For KVM, the restore of the FPU register state is performed when restoring the general-purpose guest registers before the SIE instructions is started. Because the path towards the SIE instruction is interruptible, the CIF_FPU flag must be checked again right before going into SIE. If set, the guest registers must be reloaded again by re-entering the outer SIE loop. This is the same behavior as if the SIE critical section is interrupted. Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include/asm/ctl_reg.h')
-rw-r--r--arch/s390/include/asm/ctl_reg.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/include/asm/ctl_reg.h b/arch/s390/include/asm/ctl_reg.h
index d7697ab802f6..17a373576868 100644
--- a/arch/s390/include/asm/ctl_reg.h
+++ b/arch/s390/include/asm/ctl_reg.h
@@ -46,6 +46,8 @@ static inline void __ctl_clear_bit(unsigned int cr, unsigned int bit)
__ctl_load(reg, cr, cr);
}
+void __ctl_set_vx(void);
+
void smp_ctl_set_bit(int cr, int bit);
void smp_ctl_clear_bit(int cr, int bit);

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