Re: [PATCH v5 18/22] powerpc/syscall: Remove FULL_REGS verification in system_call_exception
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-02-09 02:03:20
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Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am:
For book3s/64, FULL_REGS() is 'true' at all time, so the test voids. For others, non volatile registers are saved inconditionally. So the verification is pointless. Should one fail to do it, it would anyway be caught by the CHECK_FULL_REGS() in copy_thread() as we have removed the special versions ppc_fork() and friends. null_syscall benchmark reduction 4 cycles (332 => 328 cycles)
I wonder if we rather make a CONFIG option for a bunch of these simpler debug checks here (and also in interrupt exit, wrappers, etc) rather than remove them entirely. Thanks, Nick
quoted hunk ↗ jump to hunk
Signed-off-by: Christophe Leroy <redacted> --- arch/powerpc/kernel/interrupt.c | 1 - 1 file changed, 1 deletion(-)diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index 8fafca727b8b..55e1aa18cdb9 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c@@ -42,7 +42,6 @@ notrace long system_call_exception(long r3, long r4, long r5, if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x)) BUG_ON(!(regs->msr & MSR_RI)); BUG_ON(!(regs->msr & MSR_PR)); - BUG_ON(!FULL_REGS(regs)); BUG_ON(arch_irq_disabled_regs(regs)); #ifdef CONFIG_PPC_PKEY-- 2.25.0