linux-kernel - Re: [PATCH v3 07/26] x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs

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Message-ID: <9b814880-242b-4401-90e1-6704cbdd0751@intel.com>
Date: Fri, 30 Jan 2026 08:23:46 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, x86@...nel.org, reinette.chatre@...el.com,
 ira.weiny@...el.com, kai.huang@...el.com, dan.j.williams@...el.com,
 yilun.xu@...ux.intel.com, sagis@...gle.com, vannapurve@...gle.com,
 paulmck@...nel.org, nik.borisov@...e.com, zhenzhong.duan@...el.com,
 seanjc@...gle.com, rick.p.edgecombe@...el.com, kas@...nel.org,
 dave.hansen@...ux.intel.com, vishal.l.verma@...el.com,
 Farrah Chen <farrah.chen@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 07/26] x86/virt/seamldr: Introduce a wrapper for
 P-SEAMLDR SEAMCALLs

On 1/30/26 00:08, Chao Gao wrote:
> On Wed, Jan 28, 2026 at 03:04:55PM -0800, Dave Hansen wrote:
>> On 1/23/26 06:55, Chao Gao wrote:
>>> SEAMRET from the P-SEAMLDR clears the current VMCS structure pointed 
>>> to by the current-VMCS pointer. A VMM that invokes the P-SEAMLDR
>>> using SEAMCALL must reload the current-VMCS, if required, using the
>>> VMPTRLD instruction.
>>
>> That seems pretty mean.
>>
>> This is going to need a lot more justification for why this is an
>> absolutely necessary requirement.
> 
> AFAIK, this is a CPU implementation issue. The actual requirement is to
> evict (flush and invalidate) all VMCSs __cached in SEAM mode__, but big
> cores implement this by evicting the __entire__ VMCS cache. So, the
> current VMCS is invalidated and cleared.

But why is this a P-SEAMLDR thing and not a TDX module thing?

It seems like a bug, or at least a P-SEAMLDR implementation issue the
needs to get fixed.