linux-kernel - Re: [PATCH v8 08/16] x86/virt/tdx: Add placeholder to construct TDMRs to cover all TDX memory regions

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Message-ID: <92aba287-c839-8841-a9f7-28a2c0b3097a@intel.com>
Date:   Mon, 9 Jan 2023 16:47:50 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v8 08/16] x86/virt/tdx: Add placeholder to construct TDMRs
 to cover all TDX memory regions

On 1/9/23 16:40, Huang, Kai wrote:
> On Fri, 2023-01-06 at 11:24 -0800, Dave Hansen wrote:
...
>> Also, tdmr_sz and max_tdmrs can both be derived from 'sysinfo'.  Do they
>> really need to be stored here?
> 
> It's not mandatory to keep them here.  I did it mainly because I want to avoid
> passing 'sysinfo' as argument for almost all functions related to constructing
> TDMRs.

I don't think it hurts readability that much.  On the contrary, it makes
it more clear what data is needed for initialization.

>> If so, I think I'd probably do something
>> like this with the structure:
>>
>> struct tdmr_info_list {
>>       struct tdmr_info *tdmrs;
>>       int nr_consumed_tdmrs; // How many @tdmrs are in use
>>
>>       /* Metadata for freeing this structure: */
>>       int tdmr_sz;   // Size of one 'tdmr_info' (has a flex array)
>>       int max_tdmrs; // How many @tdmrs are allocated
>> };
>>
>> Modulo whataver folks are doing for comments these days.
> 
> Looks nice to me.  Will use.  A slight thing is 'tdmr_sz' is also used to get
> the TDMR at a given index, but not just freeing the structure.
> 
> Btw, is C++ style comment "//" OK in kernel code?

It's OK with me, but I don't think there's much consensus on it.
Probably best to stick with normal arch/x86 style for now.