On Mon, Aug 20, 2018 at 3:02 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> On Mon, 20 Aug 2018, Jinpu Wang wrote:
>
> > On Sat, Aug 18, 2018 at 2:50 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > >
> > > On Fri, 17 Aug 2018, Greg Kroah-Hartman wrote:
> > > > On Fri, Aug 17, 2018 at 02:39:00PM +0200, Jinpu Wang wrote:
> > > > >
> > > > > I found the problem, CONFIG_HOTPLUG_SMT is enable due to CONFIG_SMP,
> > > > > but I did explicitly enable CONFIG_HOTPLUG_CPU.
> > > > >
> > > > > That's why the smt dir is missing, and kernel panic when I boot with
> > > > > 'nosmt' or 'l1tf=full' probably also other combination.
> > > > >
> > > > > With CONFIG_HOTPLUG_CPU=y, it works fine so far.
> > > >
> > > > So do we need a new configuration dependancy here to resolve this
> > > > problem? Why is this not an issue in Linus's tree?
> > >
> > > That's probably the same problem on Linus tree. Have not tested it yet
> > > though. I'll have a look.
> > >
> > > Thanks,
> > >
> > > tglx
> > >
> > Yeah, it's the same problem on Linus tree.
> >
> > Probably makes sense to do the following, I can sent a formal patch if
> > you think it's right thing to do:
> >
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index b0312f8..8a52f0b 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -188,7 +188,7 @@ config X86
> > select HAVE_SYSCALL_TRACEPOINTS
> > select HAVE_UNSTABLE_SCHED_CLOCK
> > select HAVE_USER_RETURN_NOTIFIER
> > - select HOTPLUG_SMT if SMP
> > + select HOTPLUG_SMT if SMP && HOTPLUG_CPU
>
> That works, but we might as well force 'select HOTPLUG_CPU if SMP' so the
> L1TF mitigations are functional. Sigh....
>
> Thanks,
>
> tglx
right, sth like?
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b0312f8..5852948 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -188,7 +188,8 @@ config X86
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UNSTABLE_SCHED_CLOCK
select HAVE_USER_RETURN_NOTIFIER
- select HOTPLUG_SMT if SMP
+ select HOTPLUG_CPU if SMP
+ select HOTPLUG_SMT if SMP && HOTPLUG_CPU
select IRQ_FORCED_THREADING
select NEED_SG_DMA_LENGTH
select PCI_LOCKLESS_CONFIG
--
Thanks,
Jack Wang
Linux Kernel Developer
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