linux-kernel - Re: [PATCH v7 4/5] KVM: arm64: Allow cacheable stage 2 mapping using VMA flags

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Date: Thu, 19 Jun 2025 16:46:04 +0000
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Subject: Re: [PATCH v7 4/5] KVM: arm64: Allow cacheable stage 2 mapping using
 VMA flags

>> Considering the feedback, I think we may do the following here:
>> 1. Rename the device variable to S2_noncacheable to represent if the S2 is
>> going to be marked non cacheable. Otherwise S2 will be >mapped NORMAL.
>> 2. Detect what PFN has to be marked S2_noncacheable. If a PFN is not in the
>> kernel map, mark as S2 except for PFNMAP + VMA cacheable.
>   Q: 'mark as S2 except'... should be 'mark as S2_noncacheable' ?

Yeah, that's correct. Thanks for catching that.

"Detect what PFN has to be marked S2_noncacheable. If a PFN is not in the
kernel map, mark as S2_noncacheable except for PFNMAP + VMA cacheable."

> 3. Prohibit cacheable PFNMAP if hardware doesn't support FWB and CACHE DIC.
> 4. Prohibit S2 non cached mapping for cacheable VMA for all cases, whether
> pre-FWB hardware or not.