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

On 18/08/2015 00:23, Shannon Zhao wrote:

On 2015/8/18 14:36, Julien Grall wrote:

On 17/08/2015 20:19, Shannon Zhao wrote:
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?

As never say we shouldn't drop it in Xen... It's of course a nice clean
up to have if we ever happen to standardize the properties with a
different name.

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

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.

I grepped "linux," and didn't spot any "linux,uefi-*" strings.

In drivers/firmware/efi/efi.c line 478

Which is not QEMU but Linux...

Anyway, why are you speaking about old UEFI? As said in different mail,
the linux,uefi-* properties are only used internally between the EFI
stub and the kernel. Both are living in the same binary so it's not
exposed outside.

UEFI makes this minimal DT, right? To Dom0, Xen makes this minimal DT,
right? And EFI stub parses this DT through efi_get_fdt_params ==>
fdt_find_uefi_params in drivers/firmware/efi/efi.c. And
fdt_find_uefi_params uses dt_params[i].propname (e.g.
"linux,uefi-system-table") to get the matched property.

"prop = of_get_flat_dt_prop(node, dt_params[i].propname, &len);"

If we changed the property names in minimal DT but not change the
definition of dt_params[], it can't get the matched properties, right?
And if we both changed the property name in minimal DT and definition of
dt_params[], will this new kernel work well with the old UEFI which
still uses old property names to create the minimal DT?

Please read again my previous mail. The properties are created by the EFI stub (compiled within the Kernel) and neither UEFI firmware nor Xen.


Julien Grall

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