linux-kernel - Re: [PATCH v2 01/21] x86/virt/tdx: Detect SEAM

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Date:   Wed, 30 Mar 2022 12:28:14 +1300
From:   Kai Huang <kai.huang@...el.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>,
        "Tian, Kevin" <kevin.tian@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Luck, Tony" <tony.luck@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH v2 01/21] x86/virt/tdx: Detect SEAM

On Tue, 2022-03-29 at 10:52 -0700, Isaku Yamahata wrote:
> On Mon, Mar 28, 2022 at 08:10:47AM +0000,
> "Tian, Kevin" <kevin.tian@...el.com> wrote:
> 
> > > From: Huang, Kai <kai.huang@...el.com>
> > > Sent: Monday, March 28, 2022 11:55 AM
> > > 
> > > SEAMRR and TDX KeyIDs are configured by BIOS and they are static during
> > > machine's runtime.  On the other hand, TDX module can be updated and
> > > reinitialized at runtime (not supported in this series but will be supported in
> > > the future).  Theoretically, even P-SEAMLDR can be updated at runtime
> > > (although
> > > I think unlikely to be supported in Linux).  Therefore I think detecting
> > > SEAMRR
> > > and TDX KeyIDs at boot fits better.
> > 
> > If those info are static it's perfectly fine to detect them until they are
> > required... and following are not solid cases (e.g. just exposing SEAM
> > alone doesn't tell the availability of TDX) but let's also hear the opinions
> > from others.
> 
> One use case is cloud use case.  If TDX module is initialized dynamically at
> runtime, cloud management system wants to know if the physical machine is
> capable of TDX in addition to if TDX module is initialized.  Also how many TDs
> can be run on the machine even when TDX module is not initialized yet.  The
> management system will schedule TDs based on those information.

Thanks Isaku.  I'll keep current way for now.

-- 
Thanks,
-Kai