linux-kernel - Re: [RFC PATCH 0/6] KVM: guest memory: Misc enhacnement

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Message-ID: <20230619231142.0000134a.zhi.wang.linux@gmail.com>
Date:   Mon, 19 Jun 2023 23:11:42 +0300
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Vishal Annapurve <vannapurve@...gle.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>, chen.bo@...el.com,
        linux-coco@...ts.linux.dev,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Michael Roth <michael.roth@....com>
Subject: Re: [RFC PATCH 0/6] KVM: guest memory: Misc enhacnement

On Mon, 19 Jun 2023 12:11:50 -0700
Vishal Annapurve <vannapurve@...gle.com> wrote:

> On Thu, Jun 15, 2023 at 1:12___PM <isaku.yamahata@...el.com> wrote:
> > ...
> >
> > * VM type: Now we have KVM_X86_PROTECTED_VM. How do we proceed?
> >   - Keep KVM_X86_PROTECTED_VM for its use. Introduce KVM_X86_TDX_VM
> >   - Use KVM_X86_PROTECTED_VM for TDX. (If necessary, introduce another type in
> >     the future)
> >   - any other way?  
> 
> There are selftests posted[1] in context of this work, which rely on
> KVM_X86_PROTECTED_VM being just the software-only psuedo-confidential
> VMs. In future there might be more work to expand this usecase to
> full-scale VMs. So it would be better to treat protected VMs as a
> separate type which can be used on any platform without the need of
> enabling TDX/SEV functionality.
> 

Out of curiosity, is this really a valid case in practice except selftest?
It sounds to me whenever KVM_X86_PROTECTED_VM is used, it has to be tied
with a platform-specific CC type.

> TDX VM type can possibly serve as a specialized type of protected VM
> with additional arch specific capabilities enabled.
> 
> [1] - https://github.com/sean-jc/linux/commits/x86/kvm_gmem_solo