diff options
| author | James Morse <james.morse@arm.com> | 2017-11-02 12:12:37 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2017-11-02 15:55:41 +0000 |
| commit | 8d66772e869e79ffb94eed7492ca3d2267e150e8 (patch) | |
| tree | 5392449810e76786aaed93c02dfd010f1b62cfb0 /arch/arm64/kernel/entry.S | |
| parent | 41bd5b5d22b77c7300df2a2fa5397cbe785189b4 (diff) | |
| download | linux-8d66772e869e79ffb94eed7492ca3d2267e150e8.tar.gz linux-8d66772e869e79ffb94eed7492ca3d2267e150e8.tar.bz2 linux-8d66772e869e79ffb94eed7492ca3d2267e150e8.zip | |
arm64: Mask all exceptions during kernel_exit
To take RAS Exceptions as quickly as possible we need to keep SError
unmasked as much as possible. We need to mask it during kernel_exit
as taking an error from this code will overwrite the exception-registers.
Adding a naked 'disable_daif' to kernel_exit causes a performance problem
for micro-benchmarks that do no real work, (e.g. calling getpid() in a
loop). This is because the ret_to_user loop has already masked IRQs so
that the TIF_WORK_MASK thread flags can't change underneath it, adding
disable_daif is an additional self-synchronising operation.
In the future, the RAS APEI code may need to modify the TIF_WORK_MASK
flags from an SError, in which case the ret_to_user loop must mask SError
while it examines the flags.
Disable all exceptions for return to EL1. For return to EL0 get the
ret_to_user loop to leave all exceptions masked once it has done its
work, this avoids an extra pstate-write.
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index f5e851eeda4b..eff4a07c7ad7 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -221,6 +221,8 @@ alternative_else_nop_endif .macro kernel_exit, el .if \el != 0 + disable_daif + /* Restore the task's original addr_limit. */ ldr x20, [sp, #S_ORIG_ADDR_LIMIT] str x20, [tsk, #TSK_TI_ADDR_LIMIT] @@ -517,8 +519,6 @@ el1_da: mov x2, sp // struct pt_regs bl do_mem_abort - // disable interrupts before pulling preserved data off the stack - disable_irq kernel_exit 1 el1_sp_pc: /* @@ -793,7 +793,7 @@ ENDPROC(el0_irq) * and this includes saving x0 back into the kernel stack. */ ret_fast_syscall: - disable_irq // disable interrupts + disable_daif str x0, [sp, #S_X0] // returned x0 ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing and x2, x1, #_TIF_SYSCALL_WORK @@ -803,7 +803,7 @@ ret_fast_syscall: enable_step_tsk x1, x2 kernel_exit 0 ret_fast_syscall_trace: - enable_irq // enable interrupts + enable_daif b __sys_trace_return_skipped // we already saved x0 /* @@ -821,7 +821,7 @@ work_pending: * "slow" syscall return path. */ ret_to_user: - disable_irq // disable interrupts + disable_daif ldr x1, [tsk, #TSK_TI_FLAGS] and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending |