linux-kernel - Re: [PATCH v2 05/21] x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs

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Message-ID: <aWi9dlL4Wl4rA936@intel.com>
Date: Thu, 15 Jan 2026 18:12:06 +0800
From: Chao Gao <chao.gao@...el.com>
To: Xu Yilun <yilun.xu@...ux.intel.com>
CC: <linux-coco@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, <reinette.chatre@...el.com>, <ira.weiny@...el.com>,
	<kai.huang@...el.com>, <dan.j.williams@...el.com>, <sagis@...gle.com>,
	<vannapurve@...gle.com>, <paulmck@...nel.org>, <nik.borisov@...e.com>,
	"Farrah Chen" <farrah.chen@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, "Kirill A.
 Shutemov" <kas@...nel.org>
Subject: Re: [PATCH v2 05/21] x86/virt/seamldr: Introduce a wrapper for
 P-SEAMLDR SEAMCALLs

On Tue, Jan 13, 2026 at 07:08:37PM +0800, Xu Yilun wrote:
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index 58d890fe2100..6b47383d2958 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1905,6 +1905,16 @@ config INTEL_TDX_HOST
>>  
>>  	  If unsure, say N.
>>  
>> +config INTEL_TDX_MODULE_UPDATE
>> +	bool "Intel TDX module runtime update"
>> +	depends on TDX_HOST_SERVICES
>> +	help
>> +	  This enables the kernel to support TDX module runtime update. This
>> +	  allows the admin to update the TDX module to the same or any newer
>> +	  version without the need to terminate running TDX guests.
>
>I'm wondering if it is better to put this option in
>drivers/virt/coco/tdx-host. Just as TDX Connect, the
>functionalities/uAPIs are exposed in /sys/devices/faux/tdx_host. Better
>the 2 features could have aligned config pattern. The TDX Connect
>configuration is here:
>
>  https://lore.kernel.org/all/20251117022311.2443900-4-yilun.xu@linux.intel.com/

Agreed. TDX Connect and Module update should align in this matter.
I will move this kconfig under drivers/virt/coco/tdx-host.

>
>> +
>> +	  If unsure, say N.
>> +
>>  config EFI
>>  	bool "EFI runtime service support"
>>  	depends on ACPI
>> diff --git a/arch/x86/virt/vmx/tdx/Makefile b/arch/x86/virt/vmx/tdx/Makefile
>> index 90da47eb85ee..26aea3531c36 100644
>> --- a/arch/x86/virt/vmx/tdx/Makefile
>> +++ b/arch/x86/virt/vmx/tdx/Makefile
>> @@ -1,2 +1,3 @@
>>  # SPDX-License-Identifier: GPL-2.0-only
>>  obj-y += seamcall.o tdx.o
>> +obj-$(CONFIG_INTEL_TDX_MODULE_UPDATE) += seamldr.o
>
>And I'm wondering if we must disable seamldr core helpers if Update
>uAPIs are not selected. TDX core now are expected to expose various
>helpers for different features and is it necessary we have to mask
>in/out all helpers in such a fine granularity? For example we may not
>disable tdh_mem_sept_xx() helpers if KVM_INTEL is not selected.

I would rather keep this. seamldr.c will have other facilities that are for
updates only. It's better to compile them out if there are no kernel users of
them. I would agree with you if we needed to sprinkle a few #ifdef/#endif
throughout the C file, but that isn't the case as the whole file won't be
compiled.