Re: [Xen-devel] [PATCH v2] xen: arm64: Add support for Renesas RCar Gen3 H3 Salvator-X platform

[Dirk Behme <dirk.behme@xxxxxxxxxxxx>]

Hi Andre,

On 05.07.2016 16:29, Andre Przywara wrote:
> Hi,
>
> On 05/07/16 15:22, Dirk Behme wrote:
> > On 05.07.2016 15:45, Andre Przywara wrote:
> > > Hi,
> > >
> > > On 05/07/16 14:34, Julien Grall wrote:
> > > > (CC Andre)
> > > >
> > > > On 05/07/16 14:04, Dirk Behme wrote:
> > > > > On 05.07.2016 14:45, Julien Grall wrote:
> > > > > > On 05/07/16 13:09, Dirk Behme wrote:
> > > > > > > Hi Julien,
> > > > > > >
> > > > > > > On 05.07.2016 13:39, Julien Grall wrote:
> > > > > > > > Hi Dirk,
> > > > > > > >
> > > > > > > > On 05/07/16 07:37, Dirk Behme wrote:
> > > > > > > > > Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> > > > > > > > This patch looks good to me, however I would like to see the
> > > > > > > > documentation on the wiki page (see [1]) before giving any formal
> > > > > > > > ack.
> > > > > > >
> > > > > > > Ok, many thanks for your review!
> > > > > > >
> > > > > > > Yes, I understood that something more is needed.
> > > > > > >
> > > > > > >
> > > > > > > I just wonder if we keep the patch on the mailing list for a moment.
> > > > > > > With this it's publically available and we can see how's the public
> > > > > > > interest for this board.
> > > > > > >
> > > > > > > Additionally, getting Xen running on this board and describe all
> > > > > > > this in
> > > > > > > the wiki isn't that easy. You either need to modify the flashed
> > > > > > > firmware. Or, like me, load everything via a JTAG debugger ...
> > > > > > Can you details why you think it is not easy? Why do you have to
> > > > > > modify
> > > > > > the firmware? Is it because it does not boot the hypervisor in EL2?
> > > > >
> > > > > The board boots via ATF, which starts U-Boot in EL1, then. You have to
> > > > > find a way to load Xen into memory (e.g. U-Boot TFTP) and then
> > > > > switch to
> > > > > EL2 to start Xen.
> > > > But ATF is running in EL3, right? If so, can ATF just starts U-boot
> > > > in EL2?
> > > >
> > > > I have a board at home (pine64) which also uses ATF and U-Boot and is
> > > > able to boot Xen without any SMC call because the U-Boot is entered
> > > > in EL2.
> > >  From having a very quick look into the rcar ATF port on github[1] I see:
> > >
> > > +#elif (RCAR_BL33_EXECUTION_EL == BL33_EL2)
> > > +    return (uint32_t)SPSR_64(MODE_EL2, MODE_SP_ELX,
> > > DISABLE_ALL_EXCEPTIONS);
> > >
> > > So if you rebuild ATF with RCAR_BL33_EXECUTION_EL set to BL33_EL2 that
> > > should enter U-Boot in EL2.
> > >
> > > The fix for the Pine64 was equally simple and works fine since then.
> >
> > This is an other solution most probably I meant when talking about
> > "modifying the firmware" ;)
> >
> > I'm somehow unsure about the pros and cons running U-Boot at EL1 versus
> > EL2, though.
> It shouldn't matter, really. U-Boot on AArch64 (called armv8 here) is
> able to run in any exception level (in contrast to ARMv7).
> Actually running in EL2 is the architecturally recommended way, even
> with ATF (by default it drops into EL2 when returning to non-secure
> world). On Juno (and the Pine64) is works fine this way.

Could you share the U-Boot commands how you load and esp. start Xen? For 
loading you use TFTP? How do you start Xen with U-Boot, then? I think we 
have to pass the device tree address in x0 and the Linux kernel image 
address in x2. How do you do this with an U-Boot command?
Best regards

Dirk



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