Re: [PATCH v1] ACPI/IORT: Workaround for IORT ID count "minus one" issue

Hanjun Guo
2020-01-07T12:04:19Z

On 2020/1/7 1:19, Robin Murphy wrote:
> On 30/12/2019 12:27 pm, Hanjun Guo wrote:
>> The IORT spec [0] says Number of IDs = The number of IDs in the range minus
>> one, it is confusing but it was written down in the first version of the
>> IORT spec. But the IORT ID mapping function iort_id_map() did something
>> wrong from the start, which bails out if:
>>
>> the request ID >= the input base + number of IDs
>>
>> This is wrong because it ignored the "minus one", and breaks some valid
>> usecases such as ID mapping to contain single device mapping without
>> single mapping flag set.
>>
>> Pankaj Bansal proposed a solution to fix the issue [1], which bails
>> out if:
>>
>> the request ID > the input base + number of IDs
>>
>> This works as the spec defined, unfortunately some firmware didn't
>> minus one for the number of IDs in the range, and the propoased
>> solution will break those systems in this way:
>>
>> PCI hostbridge mapping entry 1:
>> Input base:  0x1000
>> ID Count:    0x100
>> Output base: 0x1000
>> Output reference: 0xC4  //ITS reference
>>
>> PCI hostbridge mapping entry 2:
>> Input base:  0x1100
>> ID Count:    0x100
>> Output base: 0x2000
>> Output reference: 0xD4  //ITS reference
>>
>> Two mapping entries which the second entry's Input base = the first
>> entry's Input base + ID count, so for requester ID 0x1100 will map
>> to ITS 0xC4 not 0xD4 if we update '>=' to '>'.
>>
>> So introduce a workaround to match the IORT's OEM information for
>> the broken firmware, also update the logic of the ID mapping for
>> firmwares report the number of IDs as the IORT spec defined, to
>> make the code compatible for both kinds of system.
>>
>> I checked the ACPI tables in the tianocore/edk2-platforms [2], only
>> HiSilicon HIP07/08 did wrong, so just add HIP07/08 to the workaround
>> info table, if we break other platforms, we can add that later.
>>
>> [0]: http://infocenter.arm.com/help/topic/com.arm.doc.den0049d/DEN0049D_IO_Remapping_Table.pdf
>> [1]: https://patchwork.kernel.org/patch/11292823/
>> [2]: https://github.com/tianocore/edk2-platforms
>>
>> Cc: Pankaj Bansal <pankaj.bansal@nxp.com>
>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>> Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
>> ---
>>
>> RFC->v1:
>> - Print warning when matched the workaround info, suggested by Pankaj.
>>
>>   drivers/acpi/arm64/iort.c | 55 ++++++++++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 52 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>> index 33f7198..60eb10d 100644
>> --- a/drivers/acpi/arm64/iort.c
>> +++ b/drivers/acpi/arm64/iort.c
>> @@ -298,6 +298,42 @@ static acpi_status iort_match_node_callback(struct acpi_iort_node *node,
>>       return status;
>>   }
>>   +struct iort_workaround_oem_info {
>> +    char oem_id[ACPI_OEM_ID_SIZE + 1];
>> +    char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
>> +    u32 oem_revision;
>> +};
>> +
>> +static bool apply_id_count_workaround;
>> +
>> +static struct iort_workaround_oem_info wa_info[] __initdata = {
>> +    {
>> +        .oem_id        = "HISI  ",
>> +        .oem_table_id    = "HIP07   ",
>> +        .oem_revision    = 0,
>> +    }, {
>> +        .oem_id        = "HISI  ",
>> +        .oem_table_id    = "HIP08   ",
>> +        .oem_revision    = 0,
>> +    }
>> +};
>> +
>> +static void __init
>> +iort_check_id_count_workaround(struct acpi_table_header *tbl)
>> +{
>> +    int i;
>> +
>> +    for (i = 0; i < ARRAY_SIZE(wa_info); i++) {
>> +        if (!memcmp(wa_info[i].oem_id, tbl->oem_id, ACPI_OEM_ID_SIZE) &&
>> +            !memcmp(wa_info[i].oem_table_id, tbl->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
>> +            wa_info[i].oem_revision == tbl->oem_revision) {
>> +            apply_id_count_workaround = true;
>> +            pr_warn(FW_BUG "ID count for ID mapping entry is wrong, applying workaround\n");
>> +            break;
>> +        }
>> +    }
>> +}
>> +
>>   static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
>>                  u32 *rid_out)
>>   {
>> @@ -314,9 +350,21 @@ static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
>>           return -ENXIO;
>>       }
>>   -    if (rid_in < map->input_base ||
>> -        (rid_in >= map->input_base + map->id_count))
>> -        return -ENXIO;
>> +    /*
>> +     * IORT spec says Number of IDs = The number of IDs in the range minus
>> +     * one, but the IORT code ingored the "minus one", and some firmware
>> +     * did that too, so apply a workaround here to keep compatible with
>> +     * both new and old versions of the firmware.
>> +     */
>> +    if (apply_id_count_workaround) {
>> +        if (rid_in < map->input_base ||
>> +            (rid_in >= map->input_base + map->id_count))
>> +            return -ENXIO;
>> +    } else {
>> +        if (rid_in < map->input_base ||
>> +            (rid_in > map->input_base + map->id_count))
>> +            return -ENXIO;
>> +    }
>
> This seems needlessly repetitive and convoluted... how about refactoring to something like:
>
>     map_max = map->input_base + map->id_count;
>     if (apply_id_count_workaround)
>         map_max--;

Much better, thanks! I will update my patch.

Thanks
Hanjun