On Fri, 2016-08-05 at 19:13 +0530, Mahesh J Salgaonkar wrote: > From: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com> > > The function pnv_restore_hyp_resource() loads the TOC into r2 from > the invalid PACA pointer before fixing r13 value. This do not affect > POWER ISA 3.0 but it does have an impact on POWER ISA 2.07 or less > leading CPU to get stuck forever.
When was this broken ? Should this get backported to stable ? > login: [ 471.830433] Processor 120 is stuck. > > > This can be easily reproducible using following steps: > - Turn off SMT > $ ppc64_cpu --smt=off > - offline/online any online cpu (Thread 0 of any core which is > online) > $ echo 0 > /sys/devices/system/cpu/cpu<num>/online > $ echo 1 > /sys/devices/system/cpu/cpu<num>/online > > For POWER ISA 2.07 or less, the last bit of HSPRG0 is set indicating > that thread is waking up from winkle. Hence, the last bit of > HSPRG0(r13) > needs to be clear before accessing it as PACA to avoid loading > invalid > values from invalid PACA pointer. > > Fix this by loading TOC after r13 register is corrected. > > Signed-off-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com> > --- > arch/powerpc/kernel/idle_book3s.S | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/idle_book3s.S > b/arch/powerpc/kernel/idle_book3s.S > index 8a56a51..45784ec 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -363,8 +363,8 @@ _GLOBAL(power9_idle_stop) > * cr3 - set to gt if waking up with partial/complete hypervisor > state loss > */ > _GLOBAL(pnv_restore_hyp_resource) > - ld r2,PACATOC(r13); > BEGIN_FTR_SECTION > + ld r2,PACATOC(r13); > /* > * POWER ISA 3. Use PSSCR to determine if we > * are waking up from deep idle state > @@ -395,6 +395,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > */ > clrldi r5,r13,63 > clrrdi r13,r13,1 > + > + /* Now that we are sure r13 is corrected, load TOC */ > + ld r2,PACATOC(r13); > cmpwi cr4,r5,1 > mtspr SPRN_HSPRG0,r13 >
