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powerpc fixes for 5.15 #5

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Fix a bug exposed by a previous fix, where running guests with certain SMT topologies
 could crash the host on Power8.
 
 Fix atomic sleep warnings when re-onlining CPUs, when PREEMPT is enabled.
 
 Thanks to: Nathan Lynch, Srikar Dronamraju, Valentin Schneider.
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Merge tag 'powerpc-5.15-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:

 - Fix a bug exposed by a previous fix, where running guests with
   certain SMT topologies could crash the host on Power8.

 - Fix atomic sleep warnings when re-onlining CPUs, when PREEMPT is
   enabled.

Thanks to Nathan Lynch, Srikar Dronamraju, and Valentin Schneider.

* tag 'powerpc-5.15-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/smp: do not decrement idle task preempt count in CPU offline
  powerpc/idle: Don't corrupt back chain when going idle
This commit is contained in:
Linus Torvalds 2021-10-21 15:30:09 -10:00
commit 0a3221b658
2 changed files with 6 additions and 6 deletions
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10
arch/powerpc/kernel/idle_book3s.S
View File

@ -126,14 +126,16 @@ _GLOBAL(idle_return_gpr_loss)
/*
* This is the sequence required to execute idle instructions, as
* specified in ISA v2.07 (and earlier). MSR[IR] and MSR[DR] must be 0.
*
* The 0(r1) slot is used to save r2 in isa206, so use that here.
* We have to store a GPR somewhere, ptesync, then reload it, and create
* a false dependency on the result of the load. It doesn't matter which
* GPR we store, or where we store it. We have already stored r2 to the
* stack at -8(r1) in isa206_idle_insn_mayloss, so use that.
*/
#define IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST) \
/* Magic NAP/SLEEP/WINKLE mode enter sequence */ \
std r2,0(r1); \
std r2,-8(r1); \
ptesync; \
ld r2,0(r1); \
ld r2,-8(r1); \
236: cmpd cr0,r2,r2; \
bne 236b; \
IDLE_INST; \

2
arch/powerpc/kernel/smp.c
View File

@ -1730,8 +1730,6 @@ void __cpu_die(unsigned int cpu)
void arch_cpu_idle_dead(void)
{
sched_preempt_enable_no_resched();
/*
* Disable on the down path. This will be re-enabled by
* start_secondary() via start_secondary_resume() below