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

Hanjun Guo
2020-01-13T07:05:18Z

On 2020/1/10 20:11, Lorenzo Pieralisi wrote:
> On Mon, Dec 30, 2019 at 08:27:04PM +0800, 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>
>
> Commit log rewritten below - please update the code (and check the
> log) as per this thread discussion.

Thank you, I will resend it ASAP.

Thanks
Hanjun