linux-kernel - Re: [PATCH v2 11/21] x86/virt/seamldr: Allocate and populate a module update request

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Message-ID: <aWnXMiIa8MzQt8qj@intel.com>
Date: Fri, 16 Jan 2026 14:14:10 +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>, "Kirill A. Shutemov" <kas@...nel.org>,
	"Dave Hansen" <dave.hansen@...ux.intel.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 v2 11/21] x86/virt/seamldr: Allocate and populate a
 module update request

On Wed, Jan 14, 2026 at 02:45:02PM +0800, Xu Yilun wrote:
>> +/* Allocate and populate a seamldr_params */
>> +static struct seamldr_params *alloc_seamldr_params(const void *module, int module_size,
>> +						   const void *sig, int sig_size)
>> +{
>> +	struct seamldr_params *params;
>> +	const u8 *ptr;
>> +	int i;
>> +
>> +	BUILD_BUG_ON(sizeof(struct seamldr_params) != SZ_4K);
>> +	if (module_size > SEAMLDR_MAX_NR_MODULE_4KB_PAGES * SZ_4K)
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	if (!IS_ALIGNED(module_size, SZ_4K) || !IS_ALIGNED(sig_size, SZ_4K) ||
>> +	    !IS_ALIGNED((unsigned long)module, SZ_4K) ||
>> +	    !IS_ALIGNED((unsigned long)sig, SZ_4K))
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	/* seamldr_params accepts one 4KB-page for sigstruct */
>> +	if (sig_size != SZ_4K)
>
>Why we check both IS_ALIGNED(sig_size, SZ_4K) and sig_size != SZ_4K, I
>assume the former is redundant.

Yes. it is redundant.

But in the next version, I will implement an extension that increases the
sigstruct size limit from a single 4KB page to four 4KB pages, so this will
become:

	/* P-SEAMLDR accepts up to 4 4KB pages for sigstruct */
	if (sig_size > 4 * SZ_4K)
		return ERR_PTR(-EINVAL);

>
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	params = (struct seamldr_params *)get_zeroed_page(GFP_KERNEL);
>> +	if (!params)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	params->scenario = SEAMLDR_SCENARIO_UPDATE;
>> +	params->sigstruct_pa = (vmalloc_to_pfn(sig) << PAGE_SHIFT) +
>
>This void * buffer comes from FW_UPLOAD callback, which is a kvmalloc
>buffer, so we do vmalloc_to_pfn() here. But that knowledge resides in
>FW_UPLOAD driver context, the kAPI entry, seamldr_install_module()
>doesn't say that. So could we add the kernel-doc to specify this
>"const u8 *data" at ...

Good suggestion. Will do.