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    SubjectRe: BUG: Bad page state in process systemd-udevd (was: [PATCH v9 bpf-next 1/9] x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP)
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    Dear Song,


    Am 28.03.22 um 08:37 schrieb Song Liu:
    > Thanks Paul for highlighting the issue.

    Thank you for getting back to me so quickly.

    > + Rick, who highlighted some potential issues with this. (also attached
    > the stack trace).

    I already had added him, but forgot to document it in the message. Sorry
    for that.

    >> On Mar 27, 2022, at 3:36 AM, Paul Menzel <pmenzel@molgen.mpg.de> wrote:

    >> Am 26.03.22 um 19:46 schrieb Paul Menzel:
    >>> #regzbot introduced: fac54e2bfb5be2b0bbf115fe80d45f59fd773048
    >>> #regzbot title: BUG: Bad page state in process systemd-udevd
    >>
    >>> Am 04.02.22 um 19:57 schrieb Song Liu:
    >>>> From: Song Liu <songliubraving@fb.com>
    >>>>
    >>>> This enables module_alloc() to allocate huge page for 2MB+ requests.
    >>>> To check the difference of this change, we need enable config
    >>>> CONFIG_PTDUMP_DEBUGFS, and call module_alloc(2MB). Before the change,
    >>>> /sys/kernel/debug/page_tables/kernel shows pte for this map. With the
    >>>> change, /sys/kernel/debug/page_tables/ show pmd for thie map.
    >>>>
    >>>> Signed-off-by: Song Liu <songliubraving@fb.com>
    >>>> ---
    >>>> arch/x86/Kconfig | 1 +
    >>>> 1 file changed, 1 insertion(+)
    >>>>
    >>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    >>>> index 6fddb63271d9..e0e0d00cf103 100644
    >>>> --- a/arch/x86/Kconfig
    >>>> +++ b/arch/x86/Kconfig
    >>>> @@ -159,6 +159,7 @@ config X86
    >>>> select HAVE_ALIGNED_STRUCT_PAGE if SLUB
    >>>> select HAVE_ARCH_AUDITSYSCALL
    >>>> select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
    >>>> + select HAVE_ARCH_HUGE_VMALLOC if HAVE_ARCH_HUGE_VMAP
    >>>> select HAVE_ARCH_JUMP_LABEL
    >>>> select HAVE_ARCH_JUMP_LABEL_RELATIVE
    >>>> select HAVE_ARCH_KASAN if X86_64
    >>> Testing Linus’ current master branch, Linux logs critical messages like below:
    >>> BUG: Bad page state in process systemd-udevd pfn:102e03
    >>> I bisected to your commit fac54e2bfb5 (x86/Kconfig: select
    >>> HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP).
    >>
    >> Sorry, I forget to mention, that this is a 32-bit (i686) userspace,
    >> but a 64-bit Linux kernel, so it might be the same issue as
    >> mentioned in commit eed1fcee556f (x86: Disable
    >> HAVE_ARCH_HUGE_VMALLOC on 32-bit x86), but didn’t fix the issue for
    >> 64-bit Linux kernel and 32-bit userspace.
    >
    > I will look more into this tomorrow. To clarify, what is the 32-bit
    > user space that triggers this? Is it systemd-udevd? Is the systemd
    > also i686?

    Yes, everything – also systemd – is i686. You can build a 32-bit VM
    image with grml-debootstrap [1]:

    sudo DEBOOTSTRAP=mmdebstrap ~/src/grml-debootstrap/grml-debootstrap
    --vm --vmfile --vmsize 3G --target /dev/shm/debian-32.img -r sid --arch
    i686 --filesystem ext4

    Then run that with QEMU, but pass the 64-bit Linux kernel to QEMU
    directly with the switches `-kernel` and `-append`, or install the amd64
    Linux kernel into the Debian VM image or the package created with `make
    bindeb-pkg` with `dpkg -i …`.


    Kind regards,

    Paul


    [1]: https://github.com/grml/grml-debootstrap/

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