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Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 3

Hi Julien,

On 2015/8/18 0:10, Julien Grall wrote:
> Hi,
> On 17/08/2015 06:01, Shannon Zhao wrote:
>> On 2015/8/14 23:17, Julien Grall wrote:
>>> On 14/08/15 15:59, Shannon Zhao wrote:
>>>> 2. Create minimal DT to pass required information to Dom0
>>>> ----------------------------------------------------------
>>>> The minimal DT mainly passes Dom0 bootargs, address and size of initrd
>>>> (if available), address and size of uefi system table, address and size
>>>> of uefi memory table, uefi-mmap-desc-size and uefi-mmap-desc-ver.
>>>> 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>;
>>>>          linux,uefi-system-table = <0xXXXXXXXX>;
>>>>          linux,uefi-mmap-start = <0xXXXXXXXX>;
>>>>          linux,uefi-mmap-size = <0xXXXXXXXX>;
>>>>          linux,uefi-mmap-desc-size = <0xXXXXXXXX>;
>>>>          linux,uefi-mmap-desc-ver = <0xXXXXXXXX>;
>>>>      };
>>>> };
>>>> For details loook at
>>>> https://github.com/torvalds/linux/blob/master/Documentation/arm/uefi.txt
>>> I would have expect a summary on the discussion we had on the previous
>>> thread [1].
>>> Note that "linux,initrd-*" are well defined given that Xen, U-boot and
>>> other bootloaders are using them. And IIRC, it's Linux specific.
>>> Although, "linux,uefi-*" are not well defined (only used internally by
>>> Linux betwen the EFI stub and the kernel) and we expect other OS to use
>>> them in the future.
>>> So I would prefer to the "linux," dropped for them.
>> Yes, I think it's good to drop the "linux," too. But if we drop the
>> linux, would it impact the linux kernel booting with UEFI? And why we
>> don't do it to Xen since Xen still uses "linux,"?
> I don't understand your second question.
I mean that Xen is using the property "linux,uefi*" as well, and why we
don't drop that prefix for Xen?

> For the first question, as we discussed in several mail, the property
> "linux,uefi-*" are only used internally between the stub and Linux. The
> sub is compiled in the kernel so there is no issue to change the property.
Since Linux defines the dt_params like below which is used to get EFI
info from DT, if we drop "linux," in Xen, does it need to drop the
"linux," in dt_params? If so, will this break the compatibility of
changed kernel with old UEFI? IIUC, there is not only Xen using these
properties, but also native host and QEMU guest.

static __initdata struct {
        const char name[32];
        const char propname[32];
        int offset;
        int size;
} dt_params[] = {
        UEFI_PARAM("System Table", "linux,uefi-system-table", system_table),
        UEFI_PARAM("MemMap Address", "linux,uefi-mmap-start", mmap),
        UEFI_PARAM("MemMap Size", "linux,uefi-mmap-size", mmap_size),
        UEFI_PARAM("MemMap Desc. Size", "linux,uefi-mmap-desc-size", desc_size),
        UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver)


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