6.12-stable review patch. If anyone has any objections, please let me know.
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From: Marco Crivellari marco.crivellari@suse.com
[ Upstream commit 56651128e2fbad80f632f388d6bf1f39c928267a ]
MIPS re-enables interrupts on its idle routine and performs a TIF_NEED_RESCHED check afterwards before putting the CPU to sleep.
The IRQs firing between the check and the 'wait' instruction may set the TIF_NEED_RESCHED flag. In order to deal with this possible race, IRQs interrupting __r4k_wait() rollback their return address to the beginning of __r4k_wait() so that TIF_NEED_RESCHED is checked again before going back to sleep.
However idle IRQs can also queue timers that may require a tick reprogramming through a new generic idle loop iteration but those timers would go unnoticed here because __r4k_wait() only checks TIF_NEED_RESCHED. It doesn't check for pending timers.
Fix this with fast-forwarding idle IRQs return address to the end of the idle routine instead of the beginning, so that the generic idle loop handles both TIF_NEED_RESCHED and pending timers.
CONFIG_CPU_MICROMIPS has been removed along with the nop instructions. There, NOPs are 2 byte in size, so change the code with 3 _ssnop which are always 4 byte and remove the ifdef. Added ehb to make sure the hazard is always cleared.
Fixes: c65a5480ff29 ("[MIPS] Fix potential latency problem due to non-atomic cpu_wait.") Signed-off-by: Marco Crivellari marco.crivellari@suse.com Signed-off-by: Maciej W. Rozycki macro@orcam.me.uk Acked-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Thomas Bogendoerfer tsbogend@alpha.franken.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/mips/include/asm/idle.h | 3 +- arch/mips/kernel/genex.S | 62 +++++++++++++++++++++--------------- arch/mips/kernel/idle.c | 7 ---- 3 files changed, 37 insertions(+), 35 deletions(-)
diff --git a/arch/mips/include/asm/idle.h b/arch/mips/include/asm/idle.h index 0992cad9c632e..2bc3678455ed0 100644 --- a/arch/mips/include/asm/idle.h +++ b/arch/mips/include/asm/idle.h @@ -6,8 +6,7 @@ #include <linux/linkage.h>
extern void (*cpu_wait)(void); -extern void r4k_wait(void); -extern asmlinkage void __r4k_wait(void); +extern asmlinkage void r4k_wait(void); extern void r4k_wait_irqoff(void);
static inline int using_rollback_handler(void) diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S index a572ce36a24f2..46d975d00298d 100644 --- a/arch/mips/kernel/genex.S +++ b/arch/mips/kernel/genex.S @@ -104,42 +104,52 @@ handle_vcei:
__FINIT
- .align 5 /* 32 byte rollback region */ -LEAF(__r4k_wait) - .set push - .set noreorder - /* start of rollback region */ - LONG_L t0, TI_FLAGS($28) - nop - andi t0, _TIF_NEED_RESCHED - bnez t0, 1f - nop - nop - nop -#ifdef CONFIG_CPU_MICROMIPS - nop - nop - nop - nop -#endif + /* Align to 32 bytes for the maximum idle interrupt region size. */ + .align 5 +LEAF(r4k_wait) + /* Keep the ISA bit clear for calculations on local labels here. */ +0: .fill 0 + /* Start of idle interrupt region. */ + local_irq_enable + /* + * If an interrupt lands here, before going idle on the next + * instruction, we must *NOT* go idle since the interrupt could + * have set TIF_NEED_RESCHED or caused a timer to need resched. + * Fall through -- see rollback_handler below -- and have the + * idle loop take care of things. + */ +1: .fill 0 + /* The R2 EI/EHB sequence takes 8 bytes, otherwise pad up. */ + .if 1b - 0b > 32 + .error "overlong idle interrupt region" + .elseif 1b - 0b > 8 + .align 4 + .endif +2: .fill 0 + .equ r4k_wait_idle_size, 2b - 0b + /* End of idle interrupt region; size has to be a power of 2. */ .set MIPS_ISA_ARCH_LEVEL_RAW +r4k_wait_insn: wait - /* end of rollback region (the region size must be power of two) */ -1: +r4k_wait_exit: + .set mips0 + local_irq_disable jr ra - nop - .set pop - END(__r4k_wait) + END(r4k_wait) + .previous
.macro BUILD_ROLLBACK_PROLOGUE handler FEXPORT(rollback_\handler) .set push .set noat MFC0 k0, CP0_EPC - PTR_LA k1, __r4k_wait - ori k0, 0x1f /* 32 byte rollback region */ - xori k0, 0x1f + /* Subtract/add 2 to let the ISA bit propagate through the mask. */ + PTR_LA k1, r4k_wait_insn - 2 + ori k0, r4k_wait_idle_size - 2 + .set noreorder bne k0, k1, \handler + PTR_ADDIU k0, r4k_wait_exit - r4k_wait_insn + 2 + .set reorder MTC0 k0, CP0_EPC .set pop .endm diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c index 5abc8b7340f88..80e8a04a642e0 100644 --- a/arch/mips/kernel/idle.c +++ b/arch/mips/kernel/idle.c @@ -35,13 +35,6 @@ static void __cpuidle r3081_wait(void) write_c0_conf(cfg | R30XX_CONF_HALT); }
-void __cpuidle r4k_wait(void) -{ - raw_local_irq_enable(); - __r4k_wait(); - raw_local_irq_disable(); -} - /* * This variant is preferable as it allows testing need_resched and going to * sleep depending on the outcome atomically. Unfortunately the "It is