linux-kernel - RE: [PATCH v2 03/25] x86/virt/tdx: Read essential global metadata for KVM

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Message-ID: <BL1PR11MB5978299D3FE0EA6DA0DAD0AEF7322@BL1PR11MB5978.namprd11.prod.outlook.com>
Date: Sat, 7 Dec 2024 00:00:07 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Hansen, Dave" <dave.hansen@...el.com>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Chatre, Reinette"
	<reinette.chatre@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Zhao, Yan Y" <yan.y.zhao@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>
Subject: RE: [PATCH v2 03/25] x86/virt/tdx: Read essential global metadata for
 KVM

> On 12/6/24 08:13, Huang, Kai wrote:
> > It is not safe. We need to check
> >
> >       sysinfo_td_conf->num_cpuid_config <= 32.
> >
> > If the TDX module version is not matched with the json file that was
> > used to generate the tdx_global_metadata.h, the num_cpuid_config
> > reported by the actual TDX module might exceed 32 which causes
> > out-of-bound array access.
> 
> The JSON *IS* the ABI description. It can't change between versions of the
> TDX module. It can only be extended. The "32" is not in the spec because the
> spec refers to the JSON!

Ah, yeah, agreed, the "spec refers to the JSON".  :-)