Re: Design doc of adding ACPI support for arm64 on Xen - version 5

[Shannon Zhao <zhaoshenglong@huawei.com>]

On 2015/9/2 20:18, Ian Campbell wrote:
> On Fri, 2015-08-28 at 17:45 +0800, Shannon Zhao wrote:
>>
>> 1. Create minimal DT to pass required information to Dom0
>> ----------------------------------------------------------
>> The UEFI stub is a feature that extends the Image/zImage into a valid
>> UEFI PE/COFF executable, including a loader application that makes it
>> possible to load the kernel directly from the UEFI shell, boot menu, or
>> one of the lightweight bootloaders like Gummiboot or rEFInd.
>> The kernel image built with stub support remains a valid kernel image
>> for booting in non-UEFI environments and the UEFI stub will be jumped
>> over for non-UEFI environments.
>>
>> When booting in UEFI mode, the UEFI stub will create a minimal DT in
>> order to pass the command line and other informations (such as the EFI
>> memory table) to the kernel. And when booting with ACPI, kernel will get
>> command line, ACPI root table address and memory map information from
>> the minimal DT. Also, it will check if the DT contains only the /chosen
>> node to know whether it boots with DT or ACPI.
>>
>> In addition, the current names of these properties with a "linux,"
>> prefix in the minimal DT are Linux specified. It needs to standardize
>> them so that other OS(such as FreeBSD) could reuse them in the future.
> 
> I mentioned this just now in a reply to an older revision while I was
> catching up on my mail backlog but I think it is important enough to
> reiterate here on the currently latest version:
> 
> We need to discuss this possible standardisation of (some derivative of)
> this Linux internal interfaces in the appropriate forums ASAP and come to a
> wider agreement that it is acceptable than just here amongst us Xen people.
> 
> A large part of this design is predicated on this and we don't want to get
> too far down this path only to discover the rest of the world says "No,
> thanks".
> 
> See my earlier reply at 
> http://lists.xen.org/archives/html/xen-devel/2015-09/msg00189.html for some
> thoughts as to who we should be talking to.
> 

Can we start with the patch for dropping the prefix "linux," and send it
to Linux kernel ML, Linux arm kernel ML, devicetree-spec and BSD ML?
Explain why it needs to do the change and standardization. Base on this,
we could discuss it with other people from the related fields.

>> So we drop the "linux," prefix of UEFI parameters and change the names
>> in Linux kernel as well.
>>
>> An example of the minimal DT:
>> / {
>>     #address-cells = <2>;
>>     #size-cells = <1>;
>>     chosen {
>>         bootargs = "kernel=Image console=hvc0 earlycon=pl011,0x1c090000
>> root=/dev/vda2 rw rootfstype=ext4 init=/bin/sh acpi=force";
>>         linux,initrd-start = <0xXXXXXXXX>;
>>         linux,initrd-end = <0xXXXXXXXX>;
>>         uefi-system-table = <0xXXXXXXXX>;
>>         uefi-mmap-start = <0xXXXXXXXX>;
>>         uefi-mmap-size = <0xXXXXXXXX>;
>>         uefi-mmap-desc-size = <0xXXXXXXXX>;
>>         uefi-mmap-desc-ver = <0xXXXXXXXX>;
>>     };
>> };
>>
>> For details loook at
>>> https://github.com/torvalds/linux/blob/master/Documentation/arm/uefi.txt
> 
> 
> .
> 

-- 
Shannon