Re: [coreboot] ARMv8 MMU changes

[Patrick Rudolph]

Am Donnerstag, den 01.03.2018, 14:11 -0800 schrieb Julius Werner:
> Hi Patrick et. al.,
>
> Continuing from what you said on IRC, let's please discuss this
> before you spend time to work on any major changes to the ARMv8 MMU
> code. I don't think that should be necessary (especially changing the
> GRANULE_SIZE which is a complication I'd really like to avoid
> having), and I'd like to understand what you're trying to do first.
> Can you explain what memory ranges you need to map on your SoC and
> why they need to be so large?

Hi Julius,
the Cavium SoC expose the MMIO space at 1 << 47 with a size of 1 << 47.
As coreboot does use PA=VA mapping, I have to extend the VA space to 48
bit and that seems to work fine with 64KB granule.

The change in coreboot is minimal, I'm not sure if all armv8 CPUs
support's that granule, but a Kconfig should do for now.

I'd really want to avoid using a 4KB granule, as I'd have to implement
either level0 page talbes, or use PA!=VA mappings.

Regards,
Patrick
> Thanks,
> Julius

ARMv8 MMU changes

[David Hendricks]

On Thu, Mar 1, 2018 at 11:30 PM, Patrick Rudolph <
[e-mail]> wrote:
> Am Donnerstag, den 01.03.2018, 14:11 -0800 schrieb Julius Werner:
> > Hi Patrick et. al.,
> >
> > Continuing from what you said on IRC, let's please discuss this
> > before you spend time to work on any major changes to the ARMv8 MMU
> > code. I don't think that should be necessary (especially changing the
> > GRANULE_SIZE which is a complication I'd really like to avoid
> > having), and I'd like to understand what you're trying to do first.
> > Can you explain what memory ranges you need to map on your SoC and
> > why they need to be so large?
>
> Hi Julius,
> the Cavium SoC expose the MMIO space at 1 << 47 with a size of 1 << 47.
> As coreboot does use PA=VA mapping, I have to extend the VA space to 48
> bit and that seems to work fine with 64KB granule.
>
> The change in coreboot is minimal, I'm not sure if all armv8 CPUs
> support's that granule, but a Kconfig should do for now.

Yes, the architecture reference manual for ARMv8 mentions that 4KB, 16KB,
and 64KB are supported for VMSAv8-64.