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

["Ard Biesheuvel" <ardb@kernel.org>]

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.


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