Re: [Xen-devel] Problems building and running Xen on Hikey960

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 28 Nov 2018, Julien Grall wrote:
> Hi Matthew,
> 
> On 28/11/2018 06:43, Matthew Daley wrote:
> > On Mon, 26 Nov 2018 at 14:07, Matthew Daley <mattd@xxxxxxxxxxx> wrote:
> >>
> >> On Fri, 23 Nov 2018 at 09:51, Julien Grall <julien.grall@xxxxxxx> wrote:
> >>>
> >>> Hi Matthew,
> >>>
> >>> Sorry for the late answer and thank you for testing the patch.
> >>>
> >>> On 11/13/18 10:43 PM, Matthew Daley wrote:
> >>>> On Tue, 13 Nov 2018 at 02:01, Julien Grall <julien.grall@xxxxxxx> wrote:
> >>>>> On 11/11/18 1:15 AM, Matthew Daley wrote:
> >>>> I gave this a go but unfortunately the same problem occurs (error
> >>>> -9s). Just to check nothing weird is happening I added a printk to
> >>>> check the value of __pa(init_secondary) in call_psci_cpu_on, giving
> >>>> 0xdfe00180.
> >>>
> >>> I have posted a patch that disables completely the relocation [1]. Could
> >>> you have a try and see whether it works now?
> >>>
> >>> Cheers,
> >>>
> >>> [1] https://lists.xen.org/archives/html/xen-devel/2018-11/msg02638.html
> >>>
> >>> --
> >>> Julien Grall
> >>
> >>
> >> Hi Julien,
> >>
> >> Unfortunately with this patch it appears to freeze after the call to 
> >> switch_ttbr(ttbr).
> >>
> >> - Matthew
> > 
> > So looking at setup_pagetables, my understanding is that it sets up a
> > 2MiB mapping for Xen's .text section (before then splitting it into
> > 4KiB pages). However, GRUB is loading Xen in RAM at 0xB8736000 for me.
> > This isn't 2MiB aligned (and isn't in low memory either!), so I can't
> > see how this would work; it still requires relocation or a more
> > granular mapping, no?
> 
> I missed the fact that we configure the PE/COFF header with 4KB alignment.
> Therefore UEFI is free to load Xen at any address 4KB aligned.
> 
> I managed to reproduce it on some UEFI platform and came up with
> the following patch:

well done!

> commit 6b268dd4ae2b433ab7314347bada3889a483a8a5
> Author: Julien Grall <julien.grall@xxxxxxx>
> Date:   Wed Nov 28 12:59:27 2018 +0000
> 
>     xen/arm64: Request UEFI to load Xen at a 2MB aligned address
>     
>     At the moment, UEFI will load Xen at a 4KB aligned address while
>     bootloader using the Image format will load at 2MB aligned address.
>     
>     Using 2MB aligned address will help to simplify Xen boot process. So
>     also switch UEFI to load at 2MB aligned address.
>     
>     Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
>     
>     ---
>     
>         This patch should allow us to remove a lot of code in the head.S to
>         cater the 4KB case.
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 4589a37874..0d1b1202fa 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -175,7 +175,7 @@ optional_header:
>  
>  extra_header_fields:
>          .quad   0                               /* ImageBase */
> -        .long   0x1000                          /* SectionAlignment (4 
> KByte) */
> +        .long   0x200000                        /* SectionAlignment (2 
> MByte) */
>          .long   0x8                             /* FileAlignment */
>          .short  0                               /* 
> MajorOperatingSystemVersion */
>          .short  0                               /* 
> MinorOperatingSystemVersion */
> 
> 
> So now arm64 always request to be loaded at 2MB aligned address. However it 
> seems
> that arm32 only request 4KB alignment. I will rework the patch to use 4KB 
> mapping
> when setting up Xen.
> 
> Cheers,
> 
> -- 
> Julien Grall
> 

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