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powerpc: Improve 64-bit syscall entry/exit 

We unconditionally hard enable interrupts. This is unnecessary as
syscalls are expected to always be called with interrupts enabled.

While at it, we add a WARN_ON if that is not the case and
CONFIG_TRACE_IRQFLAGS is enabled (we don't want to add overhead
to the fast path when this is not set though).

Thus let's remove the enabling (and associated irq tracing) from
the syscall entry path. Also on Book3S, replace a few mfmsr
instructions with loads of PACAMSR from the PACA, which should be
faster & schedule better.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2012-03-01 15:40:23 +11:00
parent fe1952fc0a
commit 1421ae0b29
1 changed files with 23 additions and 20 deletions
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43
arch/powerpc/kernel/entry_64.S
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@ -115,28 +115,33 @@ BEGIN_FW_FTR_SECTION
END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
#endif /* CONFIG_VIRT_CPU_ACCOUNTING && CONFIG_PPC_SPLPAR */
#ifdef CONFIG_TRACE_IRQFLAGS
bl .trace_hardirqs_on
REST_GPR(0,r1)
REST_4GPRS(3,r1)
REST_2GPRS(7,r1)
addi r9,r1,STACK_FRAME_OVERHEAD
ld r12,_MSR(r1)
#endif /* CONFIG_TRACE_IRQFLAGS */
li r10,1
stb r10,PACASOFTIRQEN(r13)
stb r10,PACAHARDIRQEN(r13)
std r10,SOFTE(r1)
/*
* A syscall should always be called with interrupts enabled
* so we just unconditionally hard-enable here. When some kind
* of irq tracing is used, we additionally check that condition
* is correct
*/
#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG)
lbz r10,PACASOFTIRQEN(r13)
xori r10,r10,1
1: tdnei r10,0
EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
#endif
/* Hard enable interrupts */
#ifdef CONFIG_PPC_BOOK3E
wrteei 1
#else
mfmsr r11
ld r11,PACAKMSR(r13)
ori r11,r11,MSR_EE
mtmsrd r11,1
#endif /* CONFIG_PPC_BOOK3E */
/* We do need to set SOFTE in the stack frame or the return
* from interrupt will be painful
*/
li r10,1
std r10,SOFTE(r1)
#ifdef SHOW_SYSCALLS
bl .do_show_syscall
REST_GPR(0,r1)
@ -187,16 +192,14 @@ syscall_exit:
andi. r10,r8,MSR_RI
beq- unrecov_restore
#endif
/* Disable interrupts so current_thread_info()->flags can't change,
/*
* Disable interrupts so current_thread_info()->flags can't change,
* and so that we don't get interrupted after loading SRR0/1.
*/
#ifdef CONFIG_PPC_BOOK3E
wrteei 0
#else
mfmsr r10
rldicl r10,r10,48,1
rotldi r10,r10,16
ld r10,PACAKMSR(r13)
mtmsrd r10,1
#endif /* CONFIG_PPC_BOOK3E */
@ -308,7 +311,7 @@ syscall_exit_work:
#ifdef CONFIG_PPC_BOOK3E
wrteei 1
#else
mfmsr r10
ld r10,PACAKMSR(r13)
ori r10,r10,MSR_EE
mtmsrd r10,1
#endif /* CONFIG_PPC_BOOK3E */