Re: [edk2-devel] [PATCH v2 23/30] OvmfPkg/LoongArchVirt: Add PeiServiceTablePointerLib

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

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Hi Laszlo,

This is a good question, same as the previous email, some ARCH don't 
require running code on memory during PEI phase or other reason can not 
used the MdePkg version, so this pointer will be saved by some register, 
I saw the ArmPkg version also uses a register to save this pointer.

If I move ArmPkg version PeiServiceTablePointer to MdePkg and the method 
of getting and saving the pointer use a new library which related 
architecture, other word, the API of PeiServiceTablePointer has not 
changed, adding a new library that PeiServiceTablePointer depends on, 
the real saving and reading method completed in the new library. Do you 
think this way is better?


Thanks,
Chao
在 2023/11/9 06:22, Laszlo Ersek 写道:
> On 11/6/23 04:30, Chao Li wrote:
>> Use a register to save PeiServiceTable pointer. This Library provides
>> PeiServiceTable pointer saveing and retrieval serivces.
>>
>> BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=4584
>>
>> Cc: Ard Biesheuvel<ardb+tianocore@kernel.org>
>> Cc: Jiewen Yao<jiewen.yao@intel.com>
>> Cc: Jordan Justen<jordan.l.justen@intel.com>
>> Cc: Gerd Hoffmann<kraxel@redhat.com>
>> Signed-off-by: Chao Li<lichao@loongson.cn>
>> Co-authored-by: Xianglai Li<lixianglai@loongson.cn>
>> Co-authored-by: Bibo Mao<maobibo@loongson.cn>
>> ---
>>   .../PeiServicesTablePointer.c                 | 75 +++++++++++++++++++
>>   .../PeiServicesTablePointerLib.inf            | 31 ++++++++
>>   2 files changed, 106 insertions(+)
>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointerLib.inf
> Why is this under OvmfPkg?
>
> Laszlo
>
>> diff --git a/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c b/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
>> new file mode 100644
>> index 0000000000..dcbcb50131
>> --- /dev/null
>> +++ b/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
>> @@ -0,0 +1,75 @@
>> +/** @file
>> +  PEI Services Table Pointer Library.
>> +
>> +  Copyright (c) 2023 Loongson Technology Corporation Limited. All rights reserved.<BR>
>> +
>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>> +
>> +**/
>> +
>> +#include <PiPei.h>
>> +#include <Library/PeiServicesTablePointerLib.h>
>> +#include <Library/DebugLib.h>
>> +#include <Library/BaseLib.h>
>> +#include <Register/LoongArch64/Csr.h>
>> +
>> +/**
>> +  Caches a pointer PEI Services Table.
>> +
>> +  Caches the pointer to the PEI Services Table specified by PeiServicesTablePointer
>> +  in a platform specific manner.
>> +
>> +  If PeiServicesTablePointer is NULL, then ASSERT ().
>> +
>> +  @param    PeiServicesTablePointer   The address of PeiServices pointer.
>> +**/
>> +VOID
>> +EFIAPI
>> +SetPeiServicesTablePointer (
>> +  IN CONST EFI_PEI_SERVICES  **PeiServicesTablePointer
>> +  )
>> +{
>> +  CsrWrite (LOONGARCH_CSR_KS0, (UINTN)PeiServicesTablePointer);
>> +}
>> +
>> +/**
>> +  Retrieves the cached value of the PEI Services Table pointer.
>> +
>> +  Returns the cached value of the PEI Services Table pointer in a CPU specific manner
>> +  as specified in the CPU binding section of the Platform Initialization Pre-EFI
>> +  Initialization Core Interface Specification.
>> +
>> +  If the cached PEI Services Table pointer is NULL, then ASSERT ().
>> +
>> +  @return  The pointer to PeiServices.
>> +**/
>> +CONST EFI_PEI_SERVICES **
>> +EFIAPI
>> +GetPeiServicesTablePointer (
>> +  VOID
>> +  )
>> +{
>> +  return (CONST EFI_PEI_SERVICES **)(CsrRead (LOONGARCH_CSR_KS0));
>> +}
>> +
>> +/**
>> +Perform CPU specific actions required to migrate the PEI Services Table
>> +pointer from temporary RAM to permanent RAM.
>> +
>> +For IA32 CPUs, the PEI Services Table pointer is stored in the 4 bytes
>> +immediately preceding the Interrupt Descriptor Table (IDT) in memory.
>> +For X64 CPUs, the PEI Services Table pointer is stored in the 8 bytes
>> +immediately preceding the Interrupt Descriptor Table (IDT) in memory.
>> +For Itanium and ARM CPUs, a the PEI Services Table Pointer is stored in
>> +a dedicated CPU register.  This means that there is no memory storage
>> +associated with storing the PEI Services Table pointer, so no additional
>> +migration actions are required for Itanium or ARM CPUs.
>> +**/
>> +VOID
>> +EFIAPI
>> +MigratePeiServicesTablePointer (
>> +  VOID
>> +  )
>> +{
>> +  return;
>> +}
>> diff --git a/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointerLib.inf b/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointerLib.inf
>> new file mode 100644
>> index 0000000000..274cb2f781
>> --- /dev/null
>> +++ b/OvmfPkg/LoongArchVirt/Library/PeiServicesTablePointerLib/PeiServicesTablePointerLib.inf
>> @@ -0,0 +1,31 @@
>> +## @file
>> +#  PEI Services Table Pointer Library.
>> +#
>> +#  Copyright (c) 2023 Loongson Technology Corporation Limited. All rights reserved.<BR>
>> +#
>> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
>> +#
>> +##
>> +[Defines]
>> +  INF_VERSION                    = 0x00010005
>> +  BASE_NAME                      = PeiServicesTablePointerLib
>> +  FILE_GUID                      = 098B0DB0-AD01-8886-D409-90CBC7E89154
>> +  MODULE_TYPE                    = PEIM
>> +  VERSION_STRING                 = 1.0
>> +  LIBRARY_CLASS                  = PeiServicesTablePointerLib|PEIM PEI_CORE SEC
>> +
>> +#
>> +#  VALID_ARCHITECTURES           = LOONGARCH64
>> +#
>> +
>> +[Sources]
>> +  PeiServicesTablePointer.c
>> +
>> +[Packages]
>> +  MdePkg/MdePkg.dec
>> +
>> +[LibraryClasses]
>> +  BaseLib
>> +  DebugLib
>> +
>> +[Pcd]


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