Re: [edk2-devel] [PATCH v3 09/39] MdePkg: Add a new library named PeiServicesTablePointerLibReg

["Chao Li" <lichao@loongson.cn>]

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Hi Laszlo,


Thanks,
Chao
On 2023/11/21 22:37, Laszlo Ersek wrote:
> On 11/17/23 10:59, Chao Li wrote:
>> Since some ARCH or platform not require execute code on memory during
>> PEI phase, some values may transferred via CPU registers.
>>
>> Adding PeiServcieTablePointerLibReg to allow set and get the PEI service
>> table pointer depend by a CPU register, this library can accommodate lot
>> of platforms who not require execte code on memory during PEI phase.
>>
>> Adding PeiServiceTablePointerLibReg to allows setting and getting the
>> PEI service table pointer via CPU registers, and the library can
>> accommodate many platforms that do not need to execute code on memory
>> during the PEI phase.
>>
>> The idea of this library is derived from
>> ArmPkg/Library/PeiServicesTablePointerLib/
>>
>> BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=4584
>>
>> Cc: Michael D Kinney<michael.d.kinney@intel.com>
>> Cc: Liming Gao<gaoliming@byosoft.com.cn>
>> Cc: Zhiguang Liu<zhiguang.liu@intel.com>
>> Cc: Leif Lindholm<quic_llindhol@quicinc.com>
>> Cc: Ard Biesheuvel<ardb+tianocore@kernel.org>
>> Cc: Sami Mujawar<sami.mujawar@arm.com>
>> Cc: Laszlo Ersek<lersek@redhat.com>
>> Cc: Sunil V L<sunilvl@ventanamicro.com>
>> Signed-off-by: Chao Li<lichao@loongson.cn>
>> ---
>>   .../Library/PeiServicesTablePointerLib.h      | 37 +++++++-
>>   .../PeiServicesTablePointer.c                 | 86 +++++++++++++++++++
>>   .../PeiServicesTablePointerLib.uni            | 20 +++++
>>   .../PeiServicesTablePointerLibReg.inf         | 40 +++++++++
>>   MdePkg/MdePkg.dsc                             |  1 +
>>   5 files changed, 180 insertions(+), 4 deletions(-)
>>   create mode 100644 MdePkg/Library/PeiServicesTablePointerLibReg/PeiServicesTablePointer.c
>>   create mode 100644 MdePkg/Library/PeiServicesTablePointerLibReg/PeiServicesTablePointerLib.uni
>>   create mode 100644 MdePkg/Library/PeiServicesTablePointerLibReg/PeiServicesTablePointerLibReg.inf
> In my opinion, the PeiServicesTablePointerLib class header should not be
> extended with new interfaces. I understand that the generality is
> attractive, but it is not put to use; only the loongarch architecture
> applies the new interfaces (in the subsequent patch), and for example
> the ARM code (ArmPkg/Library/PeiServicesTablePointerLib) is not reworked
> in terms of these new interfaces.

This libarary have ability of accommodate more ARCH why not? I checked 
the PI SPEC, all ARCH except IA32 and X64 using the register mechanism, 
if this library can be approved, all of them can moved into this 
libraryso that code con be reused more, I think this library is fine.

>
> What's more, the new library interfaces, even though they are exposed in
> the lib class header, are not implemented for other architectures, so
> they aren't even callable on those arches.
The patch 10 in this series has added LoongArch instance of this 
library, please check.
>
> I'm commenting on this patch and the subsequent patch in the series
> together, as seen squashed together. NB I'm not an MdePkg maintainer, so
> this is just my opinion.
So, Mike and Liming, what do your think?
>
> (1) As noted above, the library class should not be modified.
>
> (2) Modifying the *comments* in
> "MdePkg/Include/Library/PeiServicesTablePointerLib.h" is welcome, I
> think, but then we might want to add a (separate!) patch for removing
> the Itanium language, as edk2 no longer supports Itanium.
>
> (3) The PeiServicesTablePointerLibReg instance should be called
> PeiServicesTablePointerLibCsrKs0 or just PeiServicesTablePointerLibKs0.
This library will be a public libray which using the reigster mechanism, 
so the name like PeiServiceTablePointerLibCsrKs0 would not appropriate.
>
> This follows the example of the lib instance name
> "PeiServicesTablePointerLibIdt". The whole library instance should be
> loongaarch-specific IMO; there isn't much code that's being duplicated,
> so the extra interfaces (internal or external) do not help with code
> unification.
>
> (4) "PeiServicesTablePointerLib.uni" should be named similarly (suffix
> missing).
>
> (5) BASE_NAME in the library instance INF file should be defined
> similarly (suffix missing).
>
> (6) The contents of the UNI file should be loongarch-specific, i.e. be
> explicit about CSR KS0, in both comments and string constants.
>
> (7) The comments in the library instance INF file should be similarly
> loongarch-specific.
>
> (8) I suggest dropping VALID_ARCHITECTURES altogether. If we want to
> keep it, it should exclusively say LOONGARCH64.
>
> (9) The new library instance should be listed in
> [Components.LOONGARCH64] in MdePkg.dec.
>
> This section does not exist yet; I suggest introducing it under
> [Components.RISCV64].
No, it is RISC-V area, not LOONGARCH64. And I do not recommend going 
this way. I believe this library should be a public library for register 
mechanism.
>
> (10) There need not / should not be two separate C source files; just
> access the KS0 CSR in SetPeiServicesTablePointer() and
> GetPeiServicesTablePointer() directly.
>
> (11) The new library instance should probably not introduce new
> references to Itanium.
>
> Thanks,
> Laszlo


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