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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Fri, 10 Sep 2021 19:28:49 +0200
Message-ID: <CAMj1kXG6Gu=g8P902NB2b+OvzqwJQPqQewYX5UwMiXALYAFkDw@mail.gmail.com>
Subject: Re: [PATCH v2] Revert "ACPI: Add memory semantics to acpi_os_map_memory()"
To:     Jia He <justin.he@arm.com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Will Deacon <will@kernel.org>, Len Brown <lenb@kernel.org>,
        Robert Moore <robert.moore@intel.com>,
        Erik Kaneda <erik.kaneda@intel.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@acpica.org>,
        Hanjun Guo <guohanjun@huawei.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Harb Abdulhamid <harb@amperecomputing.com>
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On Fri, 10 Sept 2021 at 16:32, Jia He <justin.he@arm.com> wrote:
>
> This reverts commit 437b38c51162f8b87beb28a833c4d5dc85fa864e.
>
> After this commit, a boot panic is alway hit on an Ampere EMAG server
> with call trace as follows:
>  Internal error: synchronous external abort: 96000410 [#1] SMP
>  Modules linked in:
>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0+ #462
>  Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 0.14 02/22/2019
>  pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [...snip...]
>  Call trace:
>   acpi_ex_system_memory_space_handler+0x26c/0x2c8
>   acpi_ev_address_space_dispatch+0x228/0x2c4
>   acpi_ex_access_region+0x114/0x268
>   acpi_ex_field_datum_io+0x128/0x1b8
>   acpi_ex_extract_from_field+0x14c/0x2ac
>   acpi_ex_read_data_from_field+0x190/0x1b8
>   acpi_ex_resolve_node_to_value+0x1ec/0x288
>   acpi_ex_resolve_to_value+0x250/0x274
>   acpi_ds_evaluate_name_path+0xac/0x124
>   acpi_ds_exec_end_op+0x90/0x410
>   acpi_ps_parse_loop+0x4ac/0x5d8
>   acpi_ps_parse_aml+0xe0/0x2c8
>   acpi_ps_execute_method+0x19c/0x1ac
>   acpi_ns_evaluate+0x1f8/0x26c
>   acpi_ns_init_one_device+0x104/0x140
>   acpi_ns_walk_namespace+0x158/0x1d0
>   acpi_ns_initialize_devices+0x194/0x218
>   acpi_initialize_objects+0x48/0x50
>   acpi_init+0xe0/0x498
>
> As mentioned by Lorenzo:
>   "We are forcing memory semantics mappings to PROT_NORMAL_NC, which
>   eMAG does not like at all and I'd need to understand why. It looks
>   like the issue happen in SystemMemory Opregion handler."
>
> Hence just revert it before everything is clear.
>

Can we try to find the root cause first? -rc1 is not even out yet, and
reverting it now means we can not resubmit it until the next merge
window.