Re: AW: AW: AW: AW: AW: AW: Xen data from meta-virtualization layer

From: Stefano Stabellini <stefano.stabellini@xilinx.com>
To: Leo Krueger <leo.krueger@zal.aero>, <Zhiqiang.Hou@nxp.com>
Cc: Julien Grall <julien@xen.org>,
	Stefano Stabellini <stefano.stabellini@xilinx.com>,
	Peng Fan <peng.fan@nxp.com>,
	"brucea@xilinx.com" <brucea@xilinx.com>,
	Cornelia Bruelhart <cornelia.bruelhart@zal.aero>,
	"oleksandr_andrushchenko@epam.com"
	<oleksandr_andrushchenko@epam.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Bertrand.Marquis@arm.com" <Bertrand.Marquis@arm.com>
Subject: Re: AW: AW: AW: AW: AW: AW: Xen data from meta-virtualization layer
Date: Tue, 24 Nov 2020 18:14:51 -0800	[thread overview]
Message-ID: <alpine.DEB.2.21.2011241743490.7979@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <HE1PR05MB4794FE31A2BDE8BC458D81848BFB0@HE1PR05MB4794.eurprd05.prod.outlook.com>

+ Zhiqiang Hou

On Tue, 24 Nov 2020, Leo Krueger wrote:
> > >>> On Tue, 17 Nov 2020, Leo Krueger wrote:
> > >>>> Hi,
> > >>>>
> > >>>> I enabled CONFIG_HAS_ITS (what a stupid mistake by me to not set it
> > >>>> before...) but then had to add the following node to my device tree
> > >>>>
> > >>>> 	gic_lpi_base: syscon@0x80000000 {
> > >>>> 		compatible = "gic-lpi-base";
> > >>
> > >> I couldn't find this compatible defined/used in Linux 5.10-rc4. @Leo,
> > >> could you clarify which flavor/version of Linux you are using?
> > >
> > > It is Linux 4.19 from Yocto (Warror release). XEN 4.13.2.
> > 
> > Do you have a link to the Linux tree? Is there any additional patches on top of
> > vanilla?
> 
> Linux tree is found here: https://github.com/kontron/linux-smarc-sal28/commits/master-LSDK-19.09
> (up to the latest commit in that branch)

[...]

> > Looking at the DT changes in [0], it looks like the node is not a child of gic@.
> > So I think Xen will map the region to Dom0.
> > 
> > There are two things that I can notice:
> >    1) This region is RAM, but I can't find any reserve node. Is there any specific
> > code in Linux to reserve it?
> >    2) The implementation in U-boot seems to suggest that the firmware will
> > configure the LPIs and then enable it. If that's the case, then Xen needs to
> > re-use the table in the DT rather than allocating a new one.

That Linux tree has no mentions of gic-lpi-base. That means that
gic-lpi-base is only used in u-boot, not in Linux. In particular the
most relevant commit is af288cb291da3abef6be0875527729296f7de7a0. 

In regards to the reserved-memory regions, maybe we are not seeing them
because Leo posted the host device tree, not the one passed at runtime
from u-boot to Linux?

If so, Leo, could you please boot Linux on native (no Xen) and get the
device tree from there at runtime using dtc -I fs -O dts
/proc/device-tree ?

However, the name of the reserved-memory region created by u-boot seems
to be "lpi_rd_table". I cannot find any mentions of lpi_rd_table in the
Linux kernel tree either.

Zhiqiang, Leo is trying to boot Xen on sAL28. Linux booting on Xen
throws errors in regards to GIC/ITS initialization. On other hardware
Xen can use and virtualize GICv3 and ITS just fine. Could you please
explain what is different about sAL28 and how Xen/Linux is expected to
use the lpi_rd_table reserved-memory region?