Re: Xen on RP4

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Sun, 1 Nov 2020, Ash Wilding wrote:
> >> I think the best compromise is still to use an ACPI string to detect
> >> the platform. For instance, would it be possible to use the OEMID
> >> fields in RSDT, XSDT, FADT?  Possibly even a combination of them?
> >>
> >> Another option might be to get the platform name from UEFI somehow. 
> >
> > I included appropriate strings in e-mail.  Suitable strings do appear
> > in `dmesg`.
> 
> 
> Just as a heads-up, SMCCC does define the optional SMCCC_ARCH_SOC_ID [1]
> function and this is listed as mandatory in the Server Base Boot Reqs
> (SBBR); see pp 15 of ARM DEN 0044F [2].

Thanks for sharing, it is good to know there is a "proper" way to do it.


> Unfortunately it looks like RPi 4's firmware doesn't currently support
> this, or at least the rpi4-uefi project [3] didn't think so as of FW
> version 1.6 [4], but I couldn't find equivalent SBBR feature tracking
> pages on that site for FW versions 1.7 or 1.8 to confirm, nor could I
> find any reference to SMCCC_ARCH_SOC_ID in the RPi 4 FW sources [5].

Well, call me an optimist but maybe it is just one patch away from
happening :-)


> On the bright side, while not very helpful in the short-term, note that
> Arm's recently announced SystemReady [6] program is an evolution of
> ServerReady (SBSA+SBBR) but for other segments and applications incl.
> Embedded, IoT, and general Linux Boot.
> 
> That means in future we should see more platform firmware supporting
> SMCCC_ARCH_SOC_ID, as the SiPs will (hopefully) want their platforms to
> be SystemReady certified.
> 
> Hope that's useful info.
> 
> Thanks,
> Ash.
> 
> [1] https://developer.arm.com/documentation/den0028/c
> [2] https://developer.arm.com/documentation/den0044/latest
> [3] https://rpi4-uefi.dev/about/
> [4] https://rpi4-uefi.dev/status-v1-6-firmware/
> [5] https://github.com/pftf/RPi4/tree/master
> [6] 
> https://developer.arm.com/architectures/system-architectures/arm-systemready
>