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s390/fpu: always enable the vector facility if it is available

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If the kernel detects that the s390 hardware supports the vector
facility, it is enabled by default at an early stage.  To force
it off, use the novx kernel parameter.  Note that there is a small
time window, where the vector facility is enabled before it is
forced to be off.

With enabling the vector facility by default, the FPU save and
restore functions can be improved.  They do not longer require
to manage expensive control register updates to enable or disable
the vector enablement control for particular processes.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Hendrik Brueckner
2015-09-29 10:04:41 +02:00
committed by Martin Schwidefsky
parent 395e6aa1d0
commit b5510d9b68
13 changed files with 70 additions and 199 deletions
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12
arch/s390/kernel/early.c
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@@ -329,10 +329,20 @@ static __init void detect_machine_facilities(void)
S390_lowcore.machine_flags |= MACHINE_FLAG_TE;
if (test_facility(51))
S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC;
if (test_facility(129))
if (test_facility(129)) {
S390_lowcore.machine_flags |= MACHINE_FLAG_VX;
__ctl_set_bit(0, 17);
}
}
static int __init disable_vector_extension(char *str)
{
S390_lowcore.machine_flags &= ~MACHINE_FLAG_VX;
__ctl_clear_bit(0, 17);
return 1;
}
early_param("novx", disable_vector_extension);
static int __init cad_setup(char *str)
{
int val;