Re: [PATCH 0/4] xen/arm: Unbreak ACPI

[André Przywara <andre.przywara@xxxxxxx>]

On 29/09/2020 22:11, Alex Bennée wrote:

Hi,

> Julien Grall <julien@xxxxxxx> writes:
> 
>> Hi Alex,
>>
>> On 29/09/2020 16:29, Alex Bennée wrote:
>>>
>>> Julien Grall <julien@xxxxxxx> writes:
>>>
>>>> From: Julien Grall <jgrall@xxxxxxxxxx>
>>>>
>>>> Hi all,
>>>>
>>>> Xen on ARM has been broken for quite a while on ACPI systems. This
>>>> series aims to fix it.
>>>>
>>>> Unfortunately I don't have a system with ACPI v6.0 or later (QEMU seems
>>>> to only support 5.1).

Does QEMU provide ACPI tables? Or is this actually EDK2 generating them?

> So I did only some light testing.

So about that v6.0 or later: it seems like the requirement comes from:
commit 1c9bd43019cd "arm/acpi: Parse FADT table and get PSCI flags":
"Since STAO table and the GIC version are introduced by ACPI 6.0, we
will check the version and only parse FADT table with version >= 6.0. If
firmware provides ACPI tables with ACPI version less than 6.0, OS will
be messed up with those information, so disable ACPI if we get an FADT
table with version less than 6.0."

STAO (and XENV) have indeed been introduced by ACPI v6.0, but those
tables are supposed to be *generated* by Xen and handed down to Dom0,
they will never be provided by firmware (or parsed) by the Xen
hypervisor. Checking the Linux code it seems to actually not (yet?)
support the STAO named list, and currently finds and uses the STAO (UART
block bit) regardless of the FADT version number.

I can't find anything GIC related in the FADT, the whole GIC information
is described in MADT.

Linux/arm64 seems to be happy with ACPI >= v5.1:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kernel/acpi.c#n148

So can we relax the v6.0 requirement, to be actually >= v5.1? That is
among the first to support ARM anyway, IIRC.

I have only a smattering about ACPI, so happy to stand corrected.

Cheers,
Andre

>>>
>>> I was hoping to get more diagnostics out to get it working under QEMU
>>> TCG so I think must of missed a step:
>>>
>>>    Loading Xen 4.15-unstable ...
>>>    Loading Linux 4.19.0-11-arm64 ...
>>>    Loading initial ramdisk ...
>>>    Using modules provided by bootloader in FDT
>>>    Xen 4.15-unstable (c/s Sat Sep 26 21:55:42 2020 +0100 git:72f3d495d0) 
>>> EFI loader
>>>    ...silence...
>>>
>>> I have a grub installed from testing on a buster base:
>>>
>>>    dpkg --status grub-arm64-efi
>>>    Version: 2.04-8
>>>
>>> With:
>>>
>>>    GRUB_CMDLINE_LINUX_DEFAULT=""
>>>    GRUB_CMDLINE_LINUX="console=ttyAMA0"
>>>    GRUB_CMDLINE_LINUX_XEN_REPLACE="console=hvc0 earlyprintk=xen"
>>>    GRUB_CMDLINE_XEN="loglvl=all guest_loglvl=all 
>>> com1=115200,8n1,0x3e8,5console=com1,vg"
>>>
>>> And I built Xen with --enable-systemd and tweaked the hypervisor .config:
>>>
>>>    CONFIG_EXPERT=y
>>>    CONFIG_ACPI=y
>>>
>>> So any pointers to make it more verbose would be helpful.
>>
>> The error is hapenning before Xen setup the console. You can get early 
>> output on QEMU if you rebuild Xen with the following .config options:
>>
>> CONFIG_DEBUG=y
>> CONFIG_EARLY_UART_CHOICE_PL011=y
>> CONFIG_EARLY_UART_PL011=y
>> CONFIG_EARLY_PRINTK=y
>> CONFIG_EARLY_UART_BASE_ADDRESS=0x09000000
>> CONFIG_EARLY_UART_PL011_BAUD_RATE=0
>> CONFIG_EARLY_PRINTK_INC="debug-pl011.inc"
> 
> OK I can see it fails on the ACPI and then tries to fall back to FDT and
> then fails to find the GIC:
> 
>   (XEN) CMDLINE[00000000f7bbe000]:chosen placeholder 
> root=UUID=cf00cd3a-066b-4146-bedf-f811d3343077 ro console=hvc0 earlyprintk=xen
>   (XEN)
>   (XEN) Command line: placeholder loglvl=all guest_loglvl=all 
> com1=115200,8n1,0x3e8,5console=com1,vg no-real-mode edd=off
>   (XEN) parameter "placeholder" unknown!
>   (XEN) parameter "no-real-mode" unknown!
>   (XEN) parameter "edd" unknown!
>   (XEN) ACPI: RSDP 138560000, 0024 (r2 BOCHS )
>   (XEN) ACPI: XSDT 138550000, 004C (r1 BOCHS  BXPCFACP        1       1000013)
>   (XEN) ACPI: FACP 138510000, 010C (r5 BOCHS  BXPCFACP        1 BXPC        1)
>   (XEN) ACPI: DSDT 138520000, 14A6 (r2 BOCHS  BXPCDSDT        1 BXPC        1)
>   (XEN) ACPI: APIC 138500000, 018C (r3 BOCHS  BXPCAPIC        1 BXPC        1)
>   (XEN) ACPI: GTDT 1384F0000, 0060 (r2 BOCHS  BXPCGTDT        1 BXPC        1)
>   (XEN) ACPI: MCFG 1384E0000, 003C (r1 BOCHS  BXPCMCFG        1 BXPC        1)
>   (XEN) ACPI: SPCR 1384D0000, 0050 (r2 BOCHS  BXPCSPCR        1 BXPC        1)
>   (XEN) Unsupported FADT revision 5.1, should be 6.0+, will disable ACPI
>   (XEN) acpi_boot_table_init: FADT not found (-22)
>   (XEN) Domain heap initialised
>   (XEN) Booting using Device Tree
>   (XEN) Platform: Generic System
>   (XEN)
>   (XEN) ****************************************
>   (XEN) Panic on CPU 0:
>   (XEN) Unable to find compatible GIC in the device tree
>   (XEN) ****************************************
>   (XEN)
>   (XEN) Reboot in five seconds...
> 
> Despite saying it is going to reboot it never manages to. Any idea how
> it is trying to reset the system?
>