This is a series to enable printk and UART console for Raspberry Pi 4.

I have been able to get Xen+dom0+domUs booting. Tested with Xen 4.12 and Linux 4.19.y (Raspberry Pi linux tree + a couple of patches). Please see [1] for build instructions and limitations.

Andre - it appears that we each independently came up with a printk configuration [2]. With this series, you'd no longer need to remember the base address, just do CONFIG_EARLY_PRINTK=rpi4.

Thanks,
Stewart Hildebrand
DornerWorks, Ltd

[1] https://github.com/dornerworks/xen-rpi4-builder
[2] https://lists.xenproject.org/archives/html/xen-users/2019-07/msg00027.html
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Hi,

Thank you for your series. Please use git-send-email so your series is threaded 
correctly and sent in plain text (not HTML!).

On 24/07/2019 15:34, Stewart Hildebrand wrote:
> This is a series to enable printk and UART console for Raspberry Pi 4.
> 
> I have been able to get Xen+dom0+domUs booting. Tested with Xen 4.12 and Linux 
> 4.19.y (Raspberry Pi linux tree + a couple of patches). Please see [1] for build 
> instructions and limitations.

I guess you are not using Andre's ATF port? If you are, then Xen 4.12 is 
definitely not safe on that platform because we don't handle reserved-region yet 
and therefore Xen may re-use some of those regions.

Also, there a few other interesting problems with the RPI4 that will need to be 
solved:
    1) The UART is sharing the same page as some other devices. We either need 
to blacklist them so they can't be used by a guest (including Dom0), or we need 
to trap and sanitize access.
    2) Xen is mapping memory using 1GB mapping. AFAIK, there are 1GB slot that 
is shared between RAM and MMIO. This will result to cache incoherency.

> 
> Andre – it appears that we each independently came up with a printk 
> configuration [2]. With this series, you’d no longer need to remember the base 
> address, just do CONFIG_EARLY_PRINTK=rpi4.

Please no more earlyprintk alias. There are no real value for them other than 
cluttering a bit more Rules.mk.

This platform will definitely need some documentation as support is still WIP. 
So the earlyprintk configuration can be written in the wiki page.

Cheers,

-- 
Julien Grall

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On Wednesday, July 24, 2019 10:47 AM, Julien Grall <julien.grall@arm.com> wrote:
>Also, there a few other interesting problems with the RPI4 that will need to be
>solved:
>    1) The UART is sharing the same page as some other devices. We either
>need
>to blacklist them so they can't be used by a guest (including Dom0), or we
>need
>to trap and sanitize access.

It's also sharing an IRQ with the other "aux" peripherals. I will send a patch to blacklist for now.

>    2) Xen is mapping memory using 1GB mapping. AFAIK, there are 1GB slot
>that
>is shared between RAM and MMIO. This will result to cache incoherency.

Thanks for the info. There is also a 1GB slot shared with GPU [1].

Stewart Hildebrand
DornerWorks, Ltd

[1] https://github.com/raspberrypi/linux/issues/3093#issuecomment-515438627

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On Wednesday, July 24, 2019 10:47 AM, Julien Grall <julien.grall@arm.com> wrote:
>Hi,
>
>Thank you for your series. Please use git-send-email so your series is threaded
>correctly and sent in plain text (not HTML!).

My apologies. I will do this next time I have something to send.

>I guess you are not using Andre's ATF port? If you are, then Xen 4.12 is
>definitely not safe on that platform because we don't handle reserved-region
>yet
>and therefore Xen may re-use some of those regions.

No, I am not. I am loading a Xen+Linux combined image and dtb directly from the Raspberry Pi's firmware/bootloader. I'm not using U-Boot, either, as that would discard the bootargs passed by the Raspberry Pi firmware.

>Please no more earlyprintk alias. There are no real value for them other than
>cluttering a bit more Rules.mk.

OK. I will drop this if there is a need for a v2 of the series. Patch 2/2 could be applied independently of the printk alias.

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