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Date:   Fri, 29 Apr 2022 06:52:21 -0700
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Subject: Re: [PATCH v3 12/21] x86/virt/tdx: Create TDMRs to cover all system
 RAM
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To:     Kai Huang <kai.huang@intel.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     seanjc@google.com, pbonzini@redhat.com, len.brown@intel.com,
        tony.luck@intel.com, rafael.j.wysocki@intel.com,
        reinette.chatre@intel.com, dan.j.williams@intel.com,
        peterz@infradead.org, ak@linux.intel.com,
        kirill.shutemov@linux.intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com,
        isaku.yamahata@intel.com
References: <cover.1649219184.git.kai.huang@intel.com>
 <6cc984d5c23e06c9c87b4c7342758b29f8c8c022.1649219184.git.kai.huang@intel.com>
 <fa4d15d5-4690-9e63-f0c9-af4b58e4325c@intel.com>
 <695f319e637e7afb33f228a230566f0c671e3a03.camel@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <695f319e637e7afb33f228a230566f0c671e3a03.camel@intel.com>
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On 4/29/22 00:24, Kai Huang wrote:
> On Thu, 2022-04-28 at 09:22 -0700, Dave Hansen wrote:
>> On 4/5/22 21:49, Kai Huang wrote:
>>> implies that one TDMR could cover multiple e820 RAM entries.  If a RAM
>>> entry spans the 1GB boundary and the former part is already covered by
>>> the previous TDMR, just create a new TDMR for the latter part.
>>>
>>> TDX only supports a limited number of TDMRs (currently 64).  Abort the
>>> TDMR construction process when the number of TDMRs exceeds this
>>> limitation.
>>
>> ... and what does this *MEAN*?  Is TDX disabled?  Does it throw away the
>> RAM?  Does it eat puppies?
> 
> How about:
> 
> 	TDX only supports a limited number of TDMRs.  Simply return error when
> 	the number of TDMRs exceeds the limitation.  TDX is disabled in this
> 	case.

Better, but two things there that need to be improved.  This is a cover
letter.  Talking at the function level ("return error") is too
low-level.  It's also slipping into passive mode "is disabled".  Fixing
those, it looks like this:

	TDX only supports a limited number of TDMRs.  Disable TDX if all
	TDMRs are consumed but there is more RAM to cover.