linux-kernel - Re: [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <1e1bec34-36bd-a719-7d3b-23ab268f7092@intel.com>
Date:   Thu, 23 Mar 2023 15:12:16 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Luck, Tony" <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "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 v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on
 demand

On 3/23/23 15:09, Huang, Kai wrote:
> 1) In TDH.SYS.INIT, ask TDX module team to return TDX_RND_NO_ENTROPY instead of
> TDX_SYS_BUSY when running out of entropy.
> 
> 2) In TDH.SYS.KEY.CONFIG, ask TDX module to return TDX_RND_NO_ENTROPY instead of
> TDX_KEY_GENERATION_FAILED when running out of entropy.  Whether
> TDX_KEY_GENERATION_FAILED should be still kept is  up to TDX module team
> (because it looks running concurrent PCONFIGs is also related).
> 
> 3) Ask TDX module to always return TDX_RND_NO_ENTROPY in _ALL_ SEAMCALLs and
> keep this behaviour for future TDX modules too.

Yes, that's all fine.

> 4) In the common seamcall(), retry on TDX_RND_NO_ENTROPY.
> 
> In terms of how many times to retry, I will use a fixed value for now, similar
> to the kernel code below:
> 
> #define RDRAND_RETRY_LOOPS      10

Heck, you could even just use RDRAND_RETRY_LOOPS directly.  It's
hard(er) to bikeshed your choice of a random number that you didn't even
pick.