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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Sat, 16 Nov 2019 12:05:52 -0800
Message-ID: <CAA9_cmc7BuWkBHadHRAxfch43KWovb6rSr2AR9y3bVue0M9EhQ@mail.gmail.com>
Subject: Re: [PATCH v2] ACPI: sysfs: Change ACPI_MASKABLE_GPE_MAX to 0x100
To:     Yunfeng Ye <yeyunfeng@huawei.com>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Linux ACPI <linux-acpi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-doc@vger.kernel.org,
        "hushiyuan@huawei.com" <hushiyuan@huawei.com>,
        "linfeilong@huawei.com" <linfeilong@huawei.com>
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On Wed, Nov 13, 2019 at 11:17 PM Yunfeng Ye <yeyunfeng@huawei.com> wrote:
>
> The commit 0f27cff8597d ("ACPI: sysfs: Make ACPI GPE mask kernel
> parameter cover all GPEs") says:
>   "Use a bitmap of size 0xFF instead of a u64 for the GPE mask so 256
>    GPEs can be masked"
>
> But the masking of GPE 0xFF it not supported and the check condition
> "gpe > ACPI_MASKABLE_GPE_MAX" is not valid because the type of gpe is
> u8.
>
> So modify the macro ACPI_MASKABLE_GPE_MAX to 0x100, and drop the "gpe >
> ACPI_MASKABLE_GPE_MAX" check. In addition, update the docs "Format" for
> acpi_mask_gpe parameter.
>
> Fixes: 0f27cff8597d ("ACPI: sysfs: Make ACPI GPE mask kernel parameter cover all GPEs")
> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
> ---
> v1 -> v2:
>  - drop the "gpe > ACPI_MASKABLE_GPE_MAX" check
>  - update the docs "Format" from <int> to <byte> for acpi_mask_gpe parameter
>  - update the commit comment
>
>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>  drivers/acpi/sysfs.c                            | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)

Bisect flags commit eb09878e1301 "ACPI: sysfs: Change
ACPI_MASKABLE_GPE_MAX to 0x100" in -next as the reason for a boot
regression in my qemu-kvm test environment. It spews:

[    1.456728] ACPI: Masking GPE 0x0.
...
[  161.721420] ACPI: Masking GPE 0x0.

...and then hangs.

A straight revert gets the configuration back on its feet.

qemu-system-x86_64 --version
QEMU emulator version 4.0.50 (v4.0.0-928-g49c6c6ac0cd8)