Re: RFC: arm64: Handling reserved memory nodes

[Leo Yan <leo.yan@xxxxxxxxxx>]

On Wed, Sep 20, 2023 at 11:36:24AM +0100, Julien Grall wrote:

[...]

> > > Could you confirm the Xen does write reserved memory nodes?  Or Xen
> > > converts the reserved memory nodes to normal memory nodes as I
> > > describe above :)
> > 
> > Xen passes the /reserved-memory node unchanged from host device tree to 
> > dom0 fdt.
> > Apart from that it creates an additional memory node covering the reserved 
> > ranges.
> > Take a look at this example run(based on qemu):
> 
> Thanks for providing an example! This is quite handy.

Yeah, thanks a lot for sharing the DT binding, Michal!

> > Host dt:
> > memory@40000000 {
> >      reg = <0x00 0x40000000 0x01 0x00>;
> >      device_type = "memory";
> > };
> > 
> > reserved-memory {
> >      #size-cells = <0x02>;
> >      #address-cells = <0x02>;
> >      ranges;
> > 
> >      test@50000000 {
> >          reg = <0x00 0x50000000 0x00 0x10000000>;
> >          no-map;
> >      };
> > };
> > 
> > Xen:
> > (XEN) MODULE[0]: 000000004ac00000 - 000000004ad65000 Xen
> > (XEN) MODULE[1]: 000000004ae00000 - 000000004ae03000 Device Tree
> > (XEN) MODULE[2]: 0000000042c00000 - 000000004aa8ea8b Ramdisk
> > (XEN) MODULE[3]: 0000000040400000 - 0000000042b30000 Kernel
> > (XEN)  RESVD[0]: 0000000050000000 - 000000005fffffff
> > ...
> > (XEN) BANK[0] 0x000000c0000000-0x00000100000000 (1024MB)
> > 
> > Linux dom0:
> > [    0.000000] OF: reserved mem: 0x0000000050000000..0x000000005fffffff 
> > (262144 KiB) nomap non-reusable test@50000000
> 
> So Linux should tell whether a region has been reserved. @Leo, can you share
> with us the serial console? Can you confirm the version of Xen you are
> using?

Sure, I will share the logs and DTS in Dom0 kernel when I can access
my machine in next week (due to I am on vacation in this week).

I am a bit suspicious that I am not aware something in my working
kernel. If have any finding, I will share back.

Thanks,
Leo