Re: [edk2-devel] [PATCH v1 20/26] OvmfPkg/LoongArchVirt: Add NorFlashQemuLib

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

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Hi Ard,


Thanks,
Chao
On 2024/5/6 18:24, Ard Biesheuvel wrote:
> On Mon, 6 May 2024 at 12:02, Chao Li<lichao@loongson.cn>  wrote:
>> Hi Gerd,
>>
>>
>> Thanks,
>> Chao
>> On 2024/3/19 16:03, Gerd Hoffmann wrote:
>>
>>    Hi,
>>
>> I can't tell the implementation scheme of the current lib and existing
>> lib implementation scheme which one is better, Could you give we some
>> advice?
>>
>> I'd suggest to merge your code as OvmfPkg/Library/FdtNorFlashQemuLib as
>> it is not really loongarch-specific.
>>
>> If you want try switch aarch64 to use the same code that'll be great,
>> but sorting that out later is also fine with me.
>>
>> If you think this design is looks better, then I'm prepare to commit this
>> change under the OvmfPkg/Library as a public library. And I will enable it
>> in aarch64 after merging this change, because I think it may be tweaked and
>> validated in aarch64 for many platforms. Do you think that is good?
>>
>> The VirtNorFlashDxe is optimized for qemu-emulated pflash.  It tries to
>> avoid switching between read and write mode much, because that operation
>> has a significant overhead in virtualization.  So it's really only used
>> by ArmVirtPkg and not lots of other arm platforms.
>>
>> I'm moving the ARM version of the library to OvmfPkg and adding the set PCD method, I have verified successfully on ArmVirtQemu.dsc(both -bios and pflash), but I found that the ArmVirtQemuKernel.dsc also depends this library, so what's the difference between the two platforms?
>>
>> When I try to verify on ArmVirtQemuKernel.dsc that it works based on -bios option,  I use the command line "qemu-system-aarch64 -M virt -cpu cortex-a57 -bios LA_Virt_FW/AARCH64/QEMU_EFI.fd -net none -serial stdio -hdb /home/lichao/Software/Qemu/SctPkg/share.imag -device ramfb -device nec-usb-xhci -device usb-mouse -device usb-kbd", and it tells me "Could not open option rom 'vgabios-ramfb.bin': No such file or directory", I tried removing the option "-device ramfb", it looks like can't work.
>>
>> How does ArmVirtQemuKernel.dsc work?
>>
> It uses the -kernel QEMU command line argument, not the -bios one.
>
> This uses the Linux/arm64 kernel boot protocol (and runs the firmware
> entirely from RAM) rather than booting from NOR flash.

Alright, I got it.

Does this mean that after this change, I just verify that the -kernel 
command line can boot the OS and that it can load/store some variables 
via the Linux OS?

If so, I have some plans:

1. Port the ARM version to OvmfPkg and add the setting PCD method. *Done*.

2. Enable the new library on ArmVirtQemu.dsc and remove the hardcode in 
INC file, verify this platform. *Done*.

3. Enable the new library on ArmVirtQemuKernel.dsc and verify this 
platform. *Just verfiy booting OS and load/store some variables via 
Linux kernel. In progress.*

4. Remove the ARM NorFlashQemuLib. *Pending.*

Is the plans mentioned above possible?

>
>
> 
>


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