linux-kernel - Re: [PATCH v3 05/21] x86/virt/tdx: Detect P-SEAMLDR and TDX module

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Message-ID: <49cc6848-47ae-9c25-f479-c5aed8c892df@intel.com>
Date:   Wed, 27 Apr 2022 07:24:03 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, pbonzini@...hat.com, len.brown@...el.com,
        tony.luck@...el.com, rafael.j.wysocki@...el.com,
        reinette.chatre@...el.com, dan.j.williams@...el.com,
        peterz@...radead.org, ak@...ux.intel.com,
        kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        isaku.yamahata@...el.com
Subject: Re: [PATCH v3 05/21] x86/virt/tdx: Detect P-SEAMLDR and TDX module

On 4/26/22 17:01, Kai Huang wrote:
> 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.

We've had a lot of problems in general with this code trying to do too
much at once.  I thought we agreed that this was going to only contain
the minimum code to make TDX functional.  It seems to be creeping to
grow bigger and bigger.

Am I remembering this wrong?