Re: [PATCH v4 2/2] xen/arm: Enlarge identity map space to 10TB

[Alexey Klimov <alexey.klimov@xxxxxxxxxx>]

On Mon, 16 Oct 2023 at 15:13, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
>
>
>
> > On 16 Oct 2023, at 15:00, Bertrand Marquis <Bertrand.Marquis@xxxxxxx> wrote:
> >
> > Hi
> >
> > +Luca and Rahul
> >
> >> On 16 Oct 2023, at 15:54, Julien Grall <julien@xxxxxxx> wrote:
> >>
> >>
> >>
> >> On 16/10/2023 09:44, Michal Orzel wrote:
> >>> Hi,
> >>
> >> Hi,
> >>
> >>> On 13/10/2023 14:26, Leo Yan wrote:
> >>>>
> >>>>
> >>>> On ADLink AVA platform (Ampere Altra SoC with 32 Arm Neoverse N1 cores),
> >>>> the physical memory regions are:
> >>>>
> >>>>  DRAM memory regions:
> >>>>    Node[0] Region[0]: 0x000080000000 - 0x0000ffffffff
> >>>>    Node[0] Region[1]: 0x080000000000 - 0x08007fffffff
> >>>>    Node[0] Region[2]: 0x080100000000 - 0x0807ffffffff
> >>>>
> >>>> The UEFI loads Xen hypervisor and DTB into the high memory, the kernel
> >>>> and ramdisk images are loaded into the low memory space:
> >>>>
> >>>>  (XEN) MODULE[0]: 00000807f6df0000 - 00000807f6f3e000 Xen
> >>>>  (XEN) MODULE[1]: 00000807f8054000 - 00000807f8056000 Device Tree
> >>>>  (XEN) MODULE[2]: 00000000fa834000 - 00000000fc5de1d5 Ramdisk
> >>>>  (XEN) MODULE[3]: 00000000fc5df000 - 00000000ffb3f810 Kernel
> >>>>
> >>>> In this case, the Xen binary is loaded above 8TB, which exceeds the
> >>>> maximum supported identity map space of 2TB in Xen. Consequently, the
> >>>> system fails to boot.
> >>>>
> >>>> This patch enlarges identity map space to 10TB, allowing module loading
> >>>> within the range of [0x0 .. 0x000009ff_ffff_ffff].
> >>>>
> >>>> Fixes: 1c78d76b67 ("xen/arm64: mm: Introduce helpers to 
> >>>> prepare/enable/disable")
> >>> I don't think a fixes tag applies here given that 2TB was just a number 
> >>> we believed is enough
> >>> and all of this is platform dependent.
> >>> This can be dropped on commit if committer agrees
> >> Xen may have booted on that platform before hand. So this would be 
> >> considered a regression and therefore a tag would be warrant.
> >>
> >> AFAICT, the commit is only present on the upcoming 4.18. So the question 
> >> is whether Xen 4.17 booted out-of-the-box on ADLink? If the answer is yes, 
> >> then we need to add a Fixes tag. But the correct one would be
> >>
> >
> > @Rahul or Luca: could you give an answer here ?
> > I know you used Xen on an AVA platform but was it booting out of the box ?
>
> I can’t say for Xen 4.17, but our nightly job has run successfully on AVA for 
> the commit 730406ab81094115d9fb5ca00ba8d53cec1279b3
> (docs/misra: add deviations.rst to document additional deviations.)
>
> We are not applying any patch for it to run on AVA.

Most likely it is because your UEFI/BIOS firmware is 2.x, for instance
2.04.100.07.
This fix if for AVA machine with older UEFI firmware 1.07.300.03.

Best regards,
Alexey