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Re: [Minios-devel] [UNIKRAFT PATCHv4 21/43] plat/kvm: Add Arm64 basic entry code

Hi Julien,

> -----Original Message-----
> From: Julien Grall
> Sent: 2018年7月20日 15:50
> To: Wei Chen <Wei.Chen@xxxxxxx>; minios-devel@xxxxxxxxxxxxxxxxxxxx;
> simon.kuenzer@xxxxxxxxx
> Cc: nd <nd@xxxxxxx>; Kaly Xin <Kaly.Xin@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT PATCHv4 21/43] plat/kvm: Add Arm64 basic
> entry code
> Hi Wei,
> On 20/07/2018 08:16, Wei Chen wrote:
> >>    - What is the state of the memory at that time? You probably want to
> >> follow what Image says: "The address range corresponding to the loaded
> >> kernel image must be cleaned to PoC".
> >
> > At the very beginning, I assume QEMU had help me sync the image memory to
> PoU
> > at least. Because guest will read image bypass the cache.
> IHMO Point of Unification is far too weak for booting in a VM. This only
> tells you that the instruction cache, data cache, translation walks will
> have the same view. You don't know if the result has reached the memory
> and may not see it when MMU and cache is disabled. You want Point of
> Coherency here.
> Anyway, in both case, you have to be careful when writing with MMU and
> cache off. So I would expect the boot code to contain cache maintenance
> in the next version.

Yes, I will invalidate the cache before MMU enable in next version.

> Cheers,
> --
> Julien Grall
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