[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH RFC 00/35] Add ACPI support for arm64 on Xen

Hi Parth,

On 04/02/2015 14:01, parth.dixit@xxxxxxxxxx wrote:
From: Parth Dixit <parth.dixit@xxxxxxxxxx>
This patch series adds ACPI support for arm64.

Thank you for sending the ACPI patch series. I will give a look at it before the connect, so we could talk about it next week.

Xen reads static tables described by ACPI standard (5.1) from uefi
and configures timer, gic and uart. ACPI tables are modified to
enable PSCI, HVC and xen specific information (grant table and
event channel interrupts) and mapped into dom0 address space.
A skeleton device tree is created to pass memory
(which cannot be passed using ACPI) and rsdp pointer to DOM0.
DOM0 parses dynamic ACPI tables and configure other peripherals.

- patches 1-19 add ACPI support for xen/uefi interface
- patches 20-35 add ACPI support for xen/dom0 interface
Last patch "xen: arm64: Add ACPI support" enables the support for ACPI
so that individual patches do not affect working xen code base.

Instructions for reproducing the setup and working code base can be found
in the following repositories
wiki : https://wiki.linaro.org/LEG/Engineering/Xen_boot_on_FVP_ACPI_UEFI
linux : 
xen : https://git.linaro.org/people/parth.dixit/xen-acpi-support/xen.git
uefi : 

Few workarounds have been made to get it working, these are as follows
1. Xen assumes that mmio regions are defined in firmware. It reads
this information from uefi tables and map's it to dom0 address space.

FWIW, this is part of the UEFI spec. So it's safe to use it ;).

Right now FVP firmware on which this series has been tested
does not contains all the mmio regions defined in ACPI supplied by
firmware, to overcome this hard coding of mmio regions is done.

What's the status of this bug? IIRC, a bug was filled last December.

2. Linux is checking if mapped pages belong to ram and when this check 
it maps RAM using ioremap, to overcome this at present this check is
disabled in linux.

Some people were working on dropping/reworking this check. What's the status?

3. Device specific interrupt information is defined in DSDT tables in ACPI.
Parsing this table is out of scope for xen so it uses dom0 to parse DSDT table
and enables the interrupt dynamically when they are enabled by dom0.

It's a design choice, not a workaround ;).

4. Grant table region and event channel interrupts are hard coded right now.

5. RSDP ponter is exposed to dom0 by using "rsdp" node, this node is not yet 
in linux and its name may get changed to "linux,acpi-rsdp" or something else.


BTW, when do you plan to send the Linux series? Did they decided about the boot protocol?


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.