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Juno MMU setup

armdev

Hi,

I was trying to change my MMU setup from 39bit address space to 40bit address space in Juno.

Previously I was successfully able to map 39bit address space by setting T0SZ=25 and using L1 level page tables.

Now I am trying to enable MMU configuring L0 level page tables but as soon as I write TCR_EL2 and T0SZ=24 I am getting "Bus error on memory operation".

I faced this issue before when I was setting wrong T0SZ value but now I am setting T0SZ=24 which should be the value for 40bit virtual space.

Is it possible in Juno to have MMU with 40bit address space > 512GB ? I read another link (Re: Re: ARMv8 mmu problem)

but it is confusing if it is possible or not as ID_AA64MMFR0_EL1 register show Juno supports 40bit and memory map states upper 512GB reserved based on above link.

I would like to know how to identify then the value of T0SZ as apart from ID register and page table granularity it seems platform memory map has to be considered ?

Another issue is I am mapping my VA -> IPA -> PA all to 39bit address space and not sure if Linux has any restriction that PA/IPA needs to be wider than VA ?

Thanks.

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