#
# Feature name: membarrier-sync-core
# Kconfig: ARCH_HAS_MEMBARRIER_SYNC_CORE
# description: arch supports core serializing membarrier
#
# Architecture requirements
#
# * arm/arm64/powerpc/s390
#
# Rely on implicit context synchronization as a result of exception return
# when returning from IPI handler, and when returning to user-space.
#
# * riscv
#
# riscv uses xRET as return from interrupt and to return to user-space.
#
# Given that xRET is not core serializing, we rely on FENCE.I for providing
# core serialization:
#
# - by calling sync_core_before_usermode() on return from interrupt (cf.
# ipi_sync_core()),
#
# - via switch_mm() and sync_core_before_usermode() (respectively, for
# uthread->uthread and kthread->uthread transitions) before returning
# to user-space.
#
# The serialization in switch_mm() is activated by prepare_sync_core_cmd().
#
# * x86
#
# x86-32 uses IRET as return from interrupt, which takes care of the IPI.
# However, it uses both IRET and SYSEXIT to go back to user-space. The IRET
# instruction is core serializing, but not SYSEXIT.
#
# x86-64 uses IRET as return from interrupt, which takes care of the IPI.
# However, it can return to user-space through either SYSRETL (compat code),
# SYSRETQ, or IRET.
#
# Given that neither SYSRET{L,Q}, nor SYSEXIT, are core serializing, we rely
# instead on write_cr3() performed by switch_mm() to provide core serialization
# after changing the current mm, and deal with the special case of kthread ->
# uthread (temporarily keeping current mm into active_mm) by issuing a
# sync_core_before_usermode() in that specific case.
#
-----------------------
| arch |status|
-----------------------
| alpha: | TODO |
| arc: | TODO |
| arm: | ok |
| arm64: | ok |
| csky: | TODO |
| hexagon: | TODO |
| loongarch: | TODO |
| m68k: | TODO |
| microblaze: | TODO |
| mips: | TODO |
| nios2: | TODO |
| openrisc: | TODO |
| parisc: | TODO |
| powerpc: | ok |
| riscv: | ok |
| s390: | ok |
| sh: | TODO |
| sparc: | TODO |
| um: | TODO |
| x86: | ok |
| xtensa: | TODO |
-----------------------
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