linux-kernel - Re: [BUG]smt sysfs dir missing on 4.4.148 and 4.14.63

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Message-ID: <CAMGffEk2FqRn0av7T-aF-TKvRAKeinm96NYjJju_T4CmUrYPkQ@mail.gmail.com>
Date:   Thu, 16 Aug 2018 18:48:31 +0200
From:   Jinpu Wang <jinpu.wang@...fitbricks.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        stable <stable@...r.kernel.org>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, konrad.wilk@...cle.com
Subject: Re: [BUG]smt sysfs dir missing on 4.4.148 and 4.14.63

On Thu, Aug 16, 2018 at 6:39 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Thu, Aug 16, 2018 at 06:28:59PM +0200, Jinpu Wang wrote:
> > On Thu, Aug 16, 2018 at 5:51 PM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Thu, Aug 16, 2018 at 05:43:23PM +0200, Jinpu Wang wrote:
> > > > Hi Greg, hi Thomas,
> > > >
> > > > I noticed /sys/devices/system/cpu/smt dir is missing on 4.4.148 and
> > > > 4.14.63, default setting.
> > >
> > > For 4.4, I would be amazed if anything was there, the backport was done
> > > only to handle the local user issue, not the "full" protection.  So
> > > please try 4.9 or 4.14.
> > Thanks for quick reply. Right, just checked. the patch for create the
> > sysfs entry is missing.
>
> What patch is that?  What is the git commit id that we missed?
>
> > > How about 4.17 and 4.18, do those trees work properly for you?
> > I guess it's the same.
> > >
> > > > Tried stable/master branch 31130a16d459 ("Merge tag
> > > > 'for-linus-4.19-rc1-tag' of
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip")
> > > > It's the same there.
> > >
> > > Ah, so we are bug compatible, good :)
> > I will try test stable master a bit more to gather the full log.
> > >
> > > > When boot with 'nosmt' kernel paramter kernel 4.14.63 panic during
> > > > boot, 4.4.148 boot fine.
> > > > The call trace seem irq related, is it known bug?
> > >
> > > You are not giving us much to go on here sorry.  We need full details,
> > > and also please cc: lkml and the other developers who worked on this.
> > > THomas is on vacation this week.
> > Now, add more developers to cc, also lkml.
> >
> > I have the config and boot dmesg attached for default setting.
>
> I see no error in your boot log, what exactly are you worried about?
2 problems here:
1 According to https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html
  I expect /sys/devices/system/cpu/smt/, but it's not.
2 kernel 4.14.63 panic when I boot with 'nosmt' or 'l1tf=full', I
attached the picture here again,
  I will try to get the full log tomorrow, also test with linus tree.
>
> confused,
>
> greg k-h

Thanks
-- 
Jack Wang
Linux Kernel Developer

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