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Message-ID: <98af78402861b1982607c5fd14b0c89403c042a6.camel@intel.com>
Subject: Re: [PATCH v3 05/21] x86/virt/tdx: Detect P-SEAMLDR and TDX module
From:   Kai Huang <kai.huang@intel.com>
To:     Dave Hansen <dave.hansen@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
Date:   Wed, 27 Apr 2022 12:01:25 +1200
In-Reply-To: <104a6959-3bd4-1e75-5e3d-5dc3ef025ed0@intel.com>
References: <cover.1649219184.git.kai.huang@intel.com>
         <b9f4d4afd244d685182ce9ab5ffdd0bf245be6e2.1649219184.git.kai.huang@intel.com>
         <104a6959-3bd4-1e75-5e3d-5dc3ef025ed0@intel.com>
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On Tue, 2022-04-26 at 13:56 -0700, Dave Hansen wrote:
> On 4/5/22 21:49, Kai Huang wrote:
> > The P-SEAMLDR (persistent SEAM loader) is the first software module that
> > runs in SEAM VMX root, responsible for loading and updating the TDX
> > module.  Both the P-SEAMLDR and the TDX module are expected to be loaded
> > before host kernel boots.
> 
> Why bother with the P-SEAMLDR here at all?  The kernel isn't loading the
> TDX module in this series.  Why not just call into the TDX module directly?

It's not absolutely needed in this series.  I choose to detect P-SEAMLDR because
detecting it can also detect the TDX module, and eventually we will need to
support P-SEAMLDR because the TDX module runtime update uses P-SEAMLDR's
SEAMCALL to do that.

Also, even for this series, detecting the P-SEAMLDR allows us to provide the P-
SEAMLDR information to user at a basic level in dmesg:

[..] tdx: P-SEAMLDR: version 0x0, vendor_id: 0x8086, build_date: 20211209,
build_num 160, major 1, minor 0

This may be useful to users, but it's not a hard requirement for this series.


-- 
Thanks,
-Kai