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

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Message-ID: <18151eb8-60ec-438b-b9fb-026efc8b848d@redhat.com>
Date: Thu, 19 Jun 2025 12:03:29 -0400
From: Donald Dutile <ddutile@...hat.com>
To: Ankit Agrawal <ankita@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
 Catalin Marinas <catalin.marinas@....com>
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Subject: Re: [PATCH v7 4/5] KVM: arm64: Allow cacheable stage 2 mapping using
 VMA flags



On 6/19/25 8:14 AM, Ankit Agrawal wrote:
> 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' ?
  
> 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.