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Date:   Wed, 23 Nov 2022 10:29:46 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Kai Huang <kai.huang@intel.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org, seanjc@google.com,
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        ying.huang@intel.com, reinette.chatre@intel.com,
        len.brown@intel.com, tony.luck@intel.com, ak@linux.intel.com,
        isaku.yamahata@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, bagasdotme@gmail.com,
        sagis@google.com, imammedo@redhat.com
Subject: Re: [PATCH v7 10/20] x86/virt/tdx: Use all system memory when
 initializing TDX module as TDX memory
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References: <cover.1668988357.git.kai.huang@intel.com>
 <9b545148275b14a8c7edef1157f8ec44dc8116ee.1668988357.git.kai.huang@intel.com>
 <eb8d0f69-7ada-a358-46ea-da15a3aeac93@intel.com>
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On Tue, Nov 22, 2022 at 04:21:38PM -0800, Dave Hansen wrote:
> > +	/*
> > +	 * All memory regions that can be used by the TDX module must be
> > +	 * passed to the TDX module during the module initialization.
> > +	 * Once this is done, all "TDX-usable" memory regions are fixed
> > +	 * during module's runtime.
> > +	 *
> > +	 * The initial support of TDX guests only allocates memory from
> > +	 * the global page allocator.  To keep things simple, for now
> > +	 * just make sure all pages in the page allocator are TDX memory.
> > +	 *
> > +	 * To achieve this, use all system memory in the core-mm at the
> > +	 * time of initializing the TDX module as TDX memory, and at the
> > +	 * meantime, reject any new memory in memory hot-add.
> > +	 *
> > +	 * This works as in practice, all boot-time present DIMM is TDX
> > +	 * convertible memory.  However if any new memory is hot-added
> > +	 * before initializing the TDX module, the initialization will
> > +	 * fail due to that memory is not covered by CMR.
> > +	 *
> > +	 * This can be enhanced in the future, i.e. by allowing adding or
> > +	 * onlining non-TDX memory to a separate node, in which case the
> > +	 * "TDX-capable" nodes and the "non-TDX-capable" nodes can exist
> > +	 * together -- the userspace/kernel just needs to make sure pages
> > +	 * for TDX guests must come from those "TDX-capable" nodes.
> > +	 *
> > +	 * Build the list of TDX memory regions as mentioned above so
> > +	 * they can be passed to the TDX module later.
> > +	 */
> 
> This is msotly Documentation/, not a code comment.  Please clean it up.

So personally, I *vastly* prefer code comments over this Documentation/
cesspit. Putting things in Documentation/ is a bit like an
old-folks-home, neatly out of the way to (bit)rot in peace.

And that whole .rst disease is making it unreadable for anybody that
still knows how to use a text editor :-(