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Re: [PATCH v2 3/7] xen/arm: Introduce frame_table and virt_to_page
- To: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Mon, 17 Mar 2025 10:51:01 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Mon, 17 Mar 2025 09:51:18 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 17/03/2025 10:33, Luca Fancellu wrote:
>
>
> Hi Michal,
>
>> On 17 Mar 2025, at 09:29, Orzel, Michal <michal.orzel@xxxxxxx> wrote:
>>
>>
>>
>> On 16/03/2025 20:24, Luca Fancellu wrote:
>>>
>>>
>>> Introduce frame_table in order to provide the implementation of
>>> virt_to_page for MPU system, move the MMU variant in mmu/mm.h.
>>>
>>> Introduce FRAMETABLE_NR that is required for 'pdx_group_valid' in
>>> pdx.c, but leave the initialisation of the frame table to a later
>>> stage.
>>> Define FRAMETABLE_SIZE for MPU to support up to 1TB of ram, as the
>>> only current implementation of armv8-r aarch64, which is cortex R82,
>>> can address up to that memory.
>> When mentioning support statements like this one, it'd be beneficial to
>> provide
>> a reference to a doc of some sort.
>
> So the only reference I have is this:
> https://developer.arm.com/Processors/Cortex-R82
>
> but I would not be confident to use the link in the commit message as it
> could go stale
> very quickly. So I’m not sure about what I can do more.
Well, not really. Max physical memory is advertised via ID_AA64MMFR0_EL1. I
found some old R82 technical manual (you can surely find the latest one and
provide reference to it - not the web page) and indeed it mentions PARange as
0b0010 which is 40bit which is 1TB. With the R82 being the only CPU model
implementing ARMv8R-AArch64, that's solid information.
~Michal
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