[PATCH] xen/arm: ACPI: Remove EXPERT dependancy, default on for ARM64

[Elliott Mitchell <ehem+xen@xxxxxxx>]

Linux requires UEFI support to be enabled on ARM64 devices.  While many
ARM64 devices lack ACPI, the writing seems to be on the wall of UEFI/ACPI
potentially taking over.  Some common devices may require ACPI table
support to boot.

For devices which can boot in either mode, continue defaulting to
device-tree.  Add warnings about using ACPI advising users of present
situation.

Signed-off-by: Elliott Mitchell <ehem+xen@xxxxxxx>
---
Okay, hopefully this is okay.  Warning in Kconfig, warning on boot.
Perhaps "default y if ARM_64" is redundant, yet if someone tries to make
it possible to boot aarch32 on a ACPI machine...

I also want a date in the message.  Theory is this won't be there
forever, so a date is essential.
---
 xen/arch/arm/Kconfig     | 7 ++++++-
 xen/arch/arm/acpi/boot.c | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index 2777388265..29624d03fa 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -32,13 +32,18 @@ menu "Architecture Features"
 source "arch/Kconfig"
 
 config ACPI
-       bool "ACPI (Advanced Configuration and Power Interface) Support" if 
EXPERT
+       bool "ACPI (Advanced Configuration and Power Interface) Support"
        depends on ARM_64
+       default y if ARM_64
        ---help---
 
          Advanced Configuration and Power Interface (ACPI) support for Xen is
          an alternative to device tree on ARM64.
 
+         Note this is presently EXPERIMENTAL.  If a given device has both
+         device-tree and ACPI support, it is presently (October 2020)
+         recommended to boot using the device-tree.
+
 config GICV3
        bool "GICv3 driver"
        depends on ARM_64 && !NEW_VGIC
diff --git a/xen/arch/arm/acpi/boot.c b/xen/arch/arm/acpi/boot.c
index 30e4bd1bc5..c0e8f85325 100644
--- a/xen/arch/arm/acpi/boot.c
+++ b/xen/arch/arm/acpi/boot.c
@@ -254,6 +254,15 @@ int __init acpi_boot_table_init(void)
                                    dt_scan_depth1_nodes, NULL) )
         goto disable;
 
+    printk("\n"
+"*************************************************************************\n"
+"*    WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING    *\n"
+"*                                                                       *\n"
+"* Xen-ARM ACPI support is EXPERIMENTAL.  It is presently (October 2020) *\n"
+"* recommended you boot your system in device-tree mode if you can.      *\n"
+"*************************************************************************\n"
+            "\n");
+
     /*
      * ACPI is disabled at this point. Enable it in order to parse
      * the ACPI tables.
-- 
2.20.1


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