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    SubjectRe: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier
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    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@intel.com>
    > Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
    > Cc: linux-acpi@vger.kernel.org
    > Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
    > Cc: Zheng, Lv <lv.zheng@intel.com>
    > Cc: Julian Wollrath <jwollrath@web.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.

    [1] https://lkml.org/lkml/2014/3/10/123
    [2] https://lkml.org/lkml/2014/3/12/311


    Thanks
    dou.

    > init/main.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/init/main.c b/init/main.c
    > index df58a41..7a09467 100644
    > --- a/init/main.c
    > +++ b/init/main.c
    > @@ -654,12 +654,12 @@ asmlinkage __visible void __init start_kernel(void)
    > kmemleak_init();
    > setup_per_cpu_pageset();
    > numa_policy_init();
    > + acpi_early_init();
    > if (late_time_init)
    > late_time_init();
    > calibrate_delay();
    > pidmap_init();
    > anon_vma_init();
    > - acpi_early_init();
    > #ifdef CONFIG_X86
    > if (efi_enabled(EFI_RUNTIME_SERVICES))
    > efi_enter_virtual_mode();
    >


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