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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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b4b56f9eca
This patch changes the syscall handler to doom (tabort) active transactions when a syscall is made and return very early without performing the syscall and keeping side effects to a minimum (no CPU accounting or system call tracing is performed). Also included is a new HWCAP2 bit, PPC_FEATURE2_HTM_NOSC, to indicate this behaviour to userspace. Currently, the system call instruction automatically suspends an active transaction which causes side effects to persist when an active transaction fails. This does change the kernel's behaviour, but in a way that was documented as unsupported. It doesn't reduce functionality as syscalls will still be performed after tsuspend; it just requires that the transaction be explicitly suspended. It also provides a consistent interface and makes the behaviour of user code substantially the same across powerpc and platforms that do not support suspended transactions (e.g. x86 and s390). Performance measurements using http://ozlabs.org/~anton/junkcode/null_syscall.c indicate the cost of a normal (non-aborted) system call increases by about 0.25%. Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
21 lines
671 B
C
21 lines
671 B
C
#ifndef _ASM_POWERPC_TM_H
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#define _ASM_POWERPC_TM_H
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/* Reason codes describing kernel causes for transaction aborts. By
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* convention, bit0 is copied to TEXASR[56] (IBM bit 7) which is set if
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* the failure is persistent. PAPR saves 0xff-0xe0 for the hypervisor.
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*/
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#define TM_CAUSE_PERSISTENT 0x01
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#define TM_CAUSE_KVM_RESCHED 0xe0 /* From PAPR */
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#define TM_CAUSE_KVM_FAC_UNAV 0xe2 /* From PAPR */
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#define TM_CAUSE_RESCHED 0xde
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#define TM_CAUSE_TLBI 0xdc
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#define TM_CAUSE_FAC_UNAV 0xda
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#define TM_CAUSE_SYSCALL 0xd8
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#define TM_CAUSE_MISC 0xd6 /* future use */
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#define TM_CAUSE_SIGNAL 0xd4
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#define TM_CAUSE_ALIGNMENT 0xd2
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#define TM_CAUSE_EMULATE 0xd0
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#endif
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