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

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Message-ID: <aXxm+ezJvwUQ4sfD@intel.com>
Date: Fri, 30 Jan 2026 16:08:25 +0800
From: Chao Gao <chao.gao@...el.com>
To: Dave Hansen <dave.hansen@...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 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.

>
>KVM folks, are you OK with this?