linux-kernel - Re: [PATCH v2 18/25] KVM: TDX: Support per-VM KVM_CAP_MAX

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Message-ID: <c63d85118848faa3b741a11d9925333fafd4ea70.camel@intel.com>
Date: Mon, 6 Jan 2025 19:09:27 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "pbonzini@...hat.com" <pbonzini@...hat.com>, "Hansen, Dave"
	<dave.hansen@...el.com>, "seanjc@...gle.com" <seanjc@...gle.com>, "Huang,
 Kai" <kai.huang@...el.com>
CC: "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "Chatre, Reinette" <reinette.chatre@...el.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 18/25] KVM: TDX: Support per-VM KVM_CAP_MAX_VCPUS
 extension check

On Sun, 2025-01-05 at 22:12 +0000, Huang, Kai wrote:
> I think we should delete this sentence in the new version of this patch since
> this sentence is now obsolete which the new patch to read essential metadata for
> KVM.
> 
> This sentence was needed since originally we had code to do (pseudo):
> 
>   if (read_sys_metadata_field(MAX_VCPUS_PER_TD, &td_conf->max_vcpus_per_td))
>       td_conf->max_vcpus_per_td = U16_MAX;
> 
> Now the above code is removed in the patch which reads essential metadata for
> KVM, and reading failure of this metadata will be fatal just like reading
> others.
> 
> It was removed because when I was trying to avoid special handling in the the
> python script when generating the metadata reading code, I found the NO_BRP_MOD
> feature was introduced to the module way after the MAX_VCPUS_PER_TD metadata was
> added, therefore practically this field will always be present for the modules
> that Linux support.
> 
> Please let me know if you have different opinion, i.e., we should still do the
> old way in the patch which reads essential metadata for KVM?

Makes sense to me.