On Fri, 30 Oct 2020 10:50:01 +0800
Ying Fang <fangyi...@huawei.com> wrote:
> Hi,
>
> I have a question on UEFI/ACPI tables setup and probing on arm64 platform.
CCing Laszlo,
who might know how it's implemented.
> Currently on arm64 platform guest can be booted with both fdt and ACPI
> supported. If ACPI is enabled, [1] says the only defined method for
> passing ACPI tables to the kernel is via the UEFI system configuration
> table. So AFAIK, ACPI Should be dependent on UEFI.
>
> What's more [2] says UEFI kernel support on the ARM architectures
> is only available through a *stub*. The stub populates the FDT /chosen
> node with some UEFI parameters describing the UEFI location info.
>
> So i dump /sys/firmware/fdt from the guest, it does have something like:
>
> /dts-v1/;
>
> / {
> #size-cells = <0x02>;
> #address-cells = <0x02>;
>
> chosen {
> linux,uefi-mmap-desc-ver = <0x01>;
> linux,uefi-mmap-desc-size = <0x30>;
> linux,uefi-mmap-size = <0x810>;
> linux,uefi-mmap-start = <0x04 0x3c0ce018>;
> linux,uefi-system-table = <0x04 0x3f8b0018>;
> bootargs =
> "BOOT_IMAGE=/vmlinuz-4.19.90-2003.4.0.0036.oe1.aarch64
> root=/dev/mapper/openeuler-root ro rd.lvm.lv=openeuler/root
> rd.lvm.lv=openeuler/swap video=VGA-1:640x480-32@60me
> smmu.bypassdev=0x1000:0x17 smmu.bypassdev=0x1000:0x15
> crashkernel=1024M,high video=efifb:off video=VGA-1:640x480-32@60me";
> linux,initrd-end = <0x04 0x3a85a5da>;
> linux,initrd-start = <0x04 0x392f2000>;
> };
> };
>
> But the question is that I did not see any code adding the uefi
> in fdt chosen node in *arm_load_dtb* or anywhere else.
> Qemu only maps the OVMF binary file into a pflash device.
> So I'm really confused on how UEFI information is provided to
> guest by qemu. Does anybody know of the details about it ?
>
> [1] https://www.kernel.org/doc/html/latest/arm64/arm-acpi.html
> [2] https://www.kernel.org/doc/Documentation/arm/uefi.rst
>
> Thanks.
> Ying
>
