linux-kernel - Re: [PATCH v4 5/8] x86/virt/tdx: Start to track all global metadata in one structure

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Message-ID: <d8351d41-b7ee-48b4-a11c-5d1cd7f39ae2@suse.com>
Date: Thu, 26 Sep 2024 09:21:15 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Kai Huang <kai.huang@...el.com>, dave.hansen@...el.com,
 kirill.shutemov@...ux.intel.com, tglx@...utronix.de, bp@...en8.de,
 peterz@...radead.org, mingo@...hat.com, hpa@...or.com,
 dan.j.williams@...el.com, seanjc@...gle.com, pbonzini@...hat.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 rick.p.edgecombe@...el.com, isaku.yamahata@...el.com, adrian.hunter@...el.com
Subject: Re: [PATCH v4 5/8] x86/virt/tdx: Start to track all global metadata
 in one structure



On 24.09.24 г. 14:28 ч., Kai Huang wrote:
> The TDX module provides a set of "Global Metadata Fields".  They report
> things like TDX module version, supported features, and fields related
> to create/run TDX guests and so on.
> 
> Currently the kernel only reads "TD Memory Region" (TDMR) related fields
> for module initialization.  There are immediate needs which require the
> TDX module initialization to read more global metadata including module
> version, supported features and "Convertible Memory Regions" (CMRs).
> 
> Also, KVM will need to read more metadata fields to support baseline TDX
> guests.  In the longer term, other TDX features like TDX Connect (which
> supports assigning trusted IO devices to TDX guest) may also require
> other kernel components such as pci/vt-d to access global metadata.
> 
> To meet all those requirements, the idea is the TDX host core-kernel to
> to provide a centralized, canonical, and read-only structure for the
> global metadata that comes out from the TDX module for all kernel
> components to use.
> 
> As the first step, introduce a new 'struct tdx_sys_info' to track all
> global metadata fields.
> 
> TDX categories global metadata fields into different "Classes".  E.g.,
> the TDMR related fields are under class "TDMR Info".  Instead of making
> 'struct tdx_sys_info' a plain structure to contain all metadata fields,
> organize them in smaller structures based on the "Class".
> 
> This allows those metadata fields to be used in finer granularity thus
> makes the code more clear.  E.g., the construct_tdmr() can just take the
> structure which contains "TDMR Info" metadata fields.
> 
> Add a new function get_tdx_sys_info() as the placeholder to read all
> metadata fields, and call it at the beginning of init_tdx_module().  For
> now it only calls get_tdx_sys_info_tdmr() to read TDMR related fields.
> 
> Note there is a functional change: get_tdx_sys_info_tdmr() is moved from
> after build_tdx_memlist() to before it, but it is fine to do so.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>