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s390/setup: Recognize sequential instruction fetching facility

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When sequential instruction fetching facility is present,
certain guarantees are provided for code patching. In particular,
atomic overwrites within 8 aligned bytes is safe from an
instruction-fetching point of view.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2024-08-28 19:06:49 +02:00
parent ee3daf7c05
commit bb91ed0ee3
2 changed files with 4 additions and 0 deletions
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2
arch/s390/include/asm/setup.h
View File

@ -34,6 +34,7 @@
#define MACHINE_FLAG_SCC BIT(17)
#define MACHINE_FLAG_PCI_MIO BIT(18)
#define MACHINE_FLAG_RDP BIT(19)
#define MACHINE_FLAG_SEQ_INSN BIT(20)
#define LPP_MAGIC BIT(31)
#define LPP_PID_MASK _AC(0xffffffff, UL)
@ -95,6 +96,7 @@ extern unsigned long mio_wb_bit_mask;
#define MACHINE_HAS_SCC (get_lowcore()->machine_flags & MACHINE_FLAG_SCC)
#define MACHINE_HAS_PCI_MIO (get_lowcore()->machine_flags & MACHINE_FLAG_PCI_MIO)
#define MACHINE_HAS_RDP (get_lowcore()->machine_flags & MACHINE_FLAG_RDP)
#define MACHINE_HAS_SEQ_INSN (get_lowcore()->machine_flags & MACHINE_FLAG_SEQ_INSN)
/*
* Console mode. Override with conmode=

2
arch/s390/kernel/early.c
View File

@ -268,6 +268,8 @@ static __init void detect_machine_facilities(void)
}
if (test_facility(194))
get_lowcore()->machine_flags |= MACHINE_FLAG_RDP;
if (test_facility(85))
get_lowcore()->machine_flags |= MACHINE_FLAG_SEQ_INSN;
}
static inline void save_vector_registers(void)