| Message ID | 20170622172616.7598-1-mikey@neuling.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
Michael Neuling <mikey@neuling.org> writes: > On POWER9 the ERAT may be incorrect on wakeup from some stop states > that lose state. This causes random segvs and illegal instructions > when these stop states are enabled. > > This patch invalidates the ERAT on wakeup on POWER9 to prevent this > from causing a problem. > > Signed-off-by: Michael Neuling <mikey@neuling.org> CC: stable?
Yes please... Would be helpful On 22 Jun. 2017 7:50 pm, "Stewart Smith" <stewart@linux.vnet.ibm.com> wrote: > Michael Neuling <mikey@neuling.org> writes: > > On POWER9 the ERAT may be incorrect on wakeup from some stop states > > that lose state. This causes random segvs and illegal instructions > > when these stop states are enabled. > > > > This patch invalidates the ERAT on wakeup on POWER9 to prevent this > > from causing a problem. > > > > Signed-off-by: Michael Neuling <mikey@neuling.org> > > CC: stable? > > -- > Stewart Smith > OPAL Architect, IBM. > >
On Fri, 2017-06-23 at 10:50 +1000, Stewart Smith wrote: > Michael Neuling <mikey@neuling.org> writes: > > On POWER9 the ERAT may be incorrect on wakeup from some stop states > > that lose state. This causes random segvs and illegal instructions > > when these stop states are enabled. > > > > This patch invalidates the ERAT on wakeup on POWER9 to prevent this > > from causing a problem. > > > > Signed-off-by: Michael Neuling <mikey@neuling.org> > > CC: stable? Yes please! Mikey
Michael Neuling <mikey@neuling.org> writes: > On POWER9 the ERAT may be incorrect on wakeup from some stop states > that lose state. This causes random segvs and illegal instructions > when these stop states are enabled. Incorrect how? Because with the ERAT flush where you've put it, there's still a good amount of code executed prior to the flush isn't there? ie. we come in at 0x100, do some of the prolog, do IDLE_TEST which takes us to pnv_powersave_wakeup, which then restores state from the paca (memory), that returns and then we check KVM ... and then finally we end up at pnv_wakeup_loss. Or is there some other path? Or is the ERAT incorrect in some specific way which means we only need to flush there? cheers > diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S > index 1ea14b96f1..ace2ad50c8 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -793,6 +793,9 @@ fastsleep_workaround_at_exit: > */ > .global pnv_wakeup_loss > pnv_wakeup_loss: > +BEGIN_FTR_SECTION > + PPC_INVALIDATE_ERAT > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > ld r1,PACAR1(r13) > BEGIN_FTR_SECTION > CHECK_HMI_INTERRUPT > -- > 2.11.0
On 06/22/2017 10:56 PM, Michael Neuling wrote: > On POWER9 the ERAT may be incorrect on wakeup from some stop states > that lose state. This causes random segvs and illegal instructions > when these stop states are enabled. > > This patch invalidates the ERAT on wakeup on POWER9 to prevent this > from causing a problem. Cant there be any real genuine ERAT error on the wake up path from these states ? Just being curious.
On Fri, 23 Jun 2017 19:33:23 +1000 Michael Ellerman <mpe@ellerman.id.au> wrote: > Michael Neuling <mikey@neuling.org> writes: > > > On POWER9 the ERAT may be incorrect on wakeup from some stop states > > that lose state. This causes random segvs and illegal instructions > > when these stop states are enabled. > > Incorrect how? It can have stale ERAT entries from another idle thread. > > Because with the ERAT flush where you've put it, there's still a good > amount of code executed prior to the flush isn't there? > > ie. we come in at 0x100, do some of the prolog, do IDLE_TEST which takes > us to pnv_powersave_wakeup, which then restores state from the paca > (memory), that returns and then we check KVM ... and then finally we end > up at pnv_wakeup_loss. In the case of an HMI, we could call into OPAL as well. > Or is there some other path? Or is the ERAT incorrect in some specific > way which means we only need to flush there? I think we're in real mode until returning from pnv_wakeup_loss so those ERATs should be the same. Except KVM, which can go to guest and switch on the MMU. My bad, I suggested putting it into pnv_wakeup_loss. Flushing at the start of pnv_powersave_wakeup should be safest. I guess we can avoid it for non-state-loss wakeups if cr3 is lt. Thanks, Nick
On Fri, 2017-06-23 at 19:33 +1000, Michael Ellerman wrote: > Michael Neuling <mikey@neuling.org> writes: > > > On POWER9 the ERAT may be incorrect on wakeup from some stop states > > that lose state. This causes random segvs and illegal instructions > > when these stop states are enabled. > > Incorrect how? As in stale. Not sure about the details. > Because with the ERAT flush where you've put it, there's still a good > amount of code executed prior to the flush isn't there? In real mode, should be ok. > ie. we come in at 0x100, do some of the prolog, do IDLE_TEST which takes > us to pnv_powersave_wakeup, which then restores state from the paca > (memory), that returns and then we check KVM ... and then finally we end > up at pnv_wakeup_loss. > > Or is there some other path? Or is the ERAT incorrect in some specific > way which means we only need to flush there? I think real mode translations are ok but I'll ask around. Cheers, Ben. > cheers > > > diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S > > index 1ea14b96f1..ace2ad50c8 100644 > > --- a/arch/powerpc/kernel/idle_book3s.S > > +++ b/arch/powerpc/kernel/idle_book3s.S > > @@ -793,6 +793,9 @@ fastsleep_workaround_at_exit: > > */ > > .global pnv_wakeup_loss > > pnv_wakeup_loss: > > +BEGIN_FTR_SECTION > > + PPC_INVALIDATE_ERAT > > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > > ld r1,PACAR1(r13) > > BEGIN_FTR_SECTION > > CHECK_HMI_INTERRUPT > > -- > > 2.11.0
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index 1ea14b96f1..ace2ad50c8 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -793,6 +793,9 @@ fastsleep_workaround_at_exit: */ .global pnv_wakeup_loss pnv_wakeup_loss: +BEGIN_FTR_SECTION + PPC_INVALIDATE_ERAT +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) ld r1,PACAR1(r13) BEGIN_FTR_SECTION CHECK_HMI_INTERRUPT
On POWER9 the ERAT may be incorrect on wakeup from some stop states that lose state. This causes random segvs and illegal instructions when these stop states are enabled. This patch invalidates the ERAT on wakeup on POWER9 to prevent this from causing a problem. Signed-off-by: Michael Neuling <mikey@neuling.org> --- arch/powerpc/kernel/idle_book3s.S | 3 +++ 1 file changed, 3 insertions(+)