Re: [edk2-devel] [PATCH v1 21/26] OvmfPkg/LoongArchVirt: Add FdtQemuFwCfgLib

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

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Hi Gerd,


Thanks,
Chao
On 2024/3/18 23:28, Gerd Hoffmann wrote:
> On Sat, Mar 16, 2024 at 10:17:00AM +0800, lixianglai wrote:
>> Hi Gerd:
>>> On Mon, Mar 11, 2024 at 02:39:31AM -0700, Chao Li wrote:
>>>> This library for PEI phase, and obtains the QemuFwCfg base address by
>>>> directly parsing the FDT, reads and writes the data in QemuFwCfg by
>>>> operating on the QemuFwCfg base address.
>>>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/FdtQemuFwCfgLib/FdtQemuFwCfgPeiLib.c
>>>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/FdtQemuFwCfgLib/FdtQemuFwCfgPeiLib.inf
>>>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/FdtQemuFwCfgLib/QemuFwCfgLibInternal.h
>>>>   create mode 100644 OvmfPkg/LoongArchVirt/Library/FdtQemuFwCfgLib/QemuFwCfgPei.c
>>> Is there anything LoongArch-specific in there?
>> No,The main function of this lib library is to obtain the fwcfg base address by parsing fdt in the pei stage,
>>   and provide access to fwcfg through mmio mode,
>>   the difference between it and the existing library is that the fwcfg base address is not hard-coded in the compilation stage,
>>   and is accessed through mmio rather than io port.
> That would be the case for risc-v and aarch64 too, although I think they
> don't need fw_cfg right now (they get all info needed via fdt).
>
> I think we should add this as OvmfPkg/Library/FdtQemuFwCfgLib.
Ok, I will commit this change under OvmfPkg/Library next time. Same to 
patch 20, I will try to adjust and verify in risc-v and aarch64 after 
merging this change.
>
>> Another point that needs to be explained is that because loongarch virtual machine runs on flash in pei phase,
>> it cannot assign the pcd global variable, so we use Hob as the global variable to store the fwcfg base address.
> I think the dynamic PCD database is stored in a HOB and you should be
> able to set PCDs them even when running from (read-only) flash.
Let's me try.
>
> take care,
>    Gerd
>
>
>
> 
>


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