linux-kernel - Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier

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Date:   Thu, 24 Aug 2017 18:38:50 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "Zheng, Lv" <lv.zheng@...el.com>, tglx@...utronix.de,
        mingo@...nel.org, hpa@...or.com, ebiederm@...ssion.com,
        bhe@...hat.com, peterz@...radead.org, izumi.taku@...fujitsu.com,
        tokunaga.keiich@...fujitsu.com, linux-acpi@...r.kernel.org,
        Julian Wollrath <jwollrath@....de>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier

On Thursday, August 24, 2017 5:54:28 AM CEST Dou Liyang wrote:
> Hi Rafael, Zheng,
> 
> At 07/31/2017 06:50 PM, Dou Liyang wrote:
> > Hi,
> >
> > At 07/14/2017 01:52 PM, Dou Liyang wrote:
> >> Linux uses acpi_early_init() to put the ACPI table management into
> >> the late stage from the early stage where the mapped ACPI tables is
> >> temporary and should be unmapped.
> >>
> >> But, now initializing interrupt delivery mode should map and parse the
> >> DMAR table earlier in the early stage. This causes an ACPI error when
> >> Linux reallocates the ACPI root tables. Because Linux doesn't unmapped
> >> the DMAR table after using in the early stage.
> >>
> >> Invoke acpi_early_init() earlier before late_time_init(), Keep the DMAR
> >> be mapped and parsed in late stage like before.
> >>
> >> Reported-by: Xiaolong Ye <xiaolong.ye@...el.com>
> >> Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
> >> Cc: linux-acpi@...r.kernel.org
> >> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> >> Cc: Zheng, Lv <lv.zheng@...el.com>
> >> Cc: Julian Wollrath <jwollrath@....de>
> >> ---
> >> Test in my own PC(Lenovo M4340).
> >> Ask help for doing regression testing for the bug said in commit
> >> c4e1acbb35e4
> >> ("ACPI / init: Invoke early ACPI initialization later").
> >>
> >
> > Now, I can prove this patch doesn't result in the bug[1] which made the
> > fast TSC calibration using PIT failed in a Thinkpad x121e (AMD E-450
> > APU).
> >
> > The true reason of the bug is enabling ACPI subsystem earlier than
> > using PIT, not the SCI setup. invoking acpi_enable_subsystem() later
> > could fix this bug as Julian tested and said[2].
> >
> > And, I found that Commit b064a8fa77df (" ACPI / init: Switch over
> > platform to the ACPI mode later") split the ACPI early initialization
> > code into acpi_early_init() and acpi_subsystem_init(). executing
> > acpi_enable_subsystem() at the original early ACPI initialization spot.
> >
> > The sequence of them shows below:
> >
> >  start_kernel
> > +---------------+
> > |
> > +--> .......
> > |
> > |    late_time_init()
> > +--> +-------+
> > |
> > +--> .......
> > |
> > |    acpi_early_init()
> > +--> +-------+
> > |
> > +--> .......
> > |
> > |   acpi_subsystem_init()
> > +-> +--------+
> >
> > We make sure the acpi_subsystem_init() is called later than
> > late_time_init(), the bug will be avoided.
> >
> > This patch changes the sequence of late_time_init() and
> > acpi_early_init(), doesn't effect acpi_subsystem_init().
> >
> > So, this patch is OK.
> >
> > Btw, Thanks very much for Borislav Petkov, he will have access to
> > Thinkpad x121e from Mid-August and will test this series.
> >
> 
> Almost one month passed, Borislav have tested this series in Thinkpad
> x121e and I also have tested in my box and QEmu again. It is OK.
> 
> BTW,
> 1) I found your commit b064a8fa77df (" ACPI / init: Switch over
> platform to the ACPI mode later") split the ACPI early initialization
> code into acpi_early_init() and acpi_subsystem_init(). Actually enabling
> the ACPI subsystem is in acpi_subsystem_init().
> 
> 2) As we discussed earlier, invoking acpi_put_table() is not good for
> this situation.
> 
> So I do this patch, Is that goot to you? Any comments will be welcome.
> 
> If it is OK, As the patches need to be re-based, and I also found
> several spelling mistake, I will send a new version next week.

OK, but does it depend on anything?  Or does anything depend on it?

It is [12/13] in a series, so it looks like it doesn't depend on the
previous patches in it, but the next one may depend on it?  Which is the
case?

Thanks,
Rafael