linux-kernel - Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free

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Message-ID: <aWrHAeMcjDpVnTBp@google.com>
Date: Fri, 16 Jan 2026 15:17:21 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: bp@...en8.de, chao.gao@...el.com, dave.hansen@...el.com, 
	isaku.yamahata@...el.com, kai.huang@...el.com, kas@...nel.org, 
	kvm@...r.kernel.org, linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	mingo@...hat.com, pbonzini@...hat.com, tglx@...utronix.de, 
	vannapurve@...gle.com, x86@...nel.org, yan.y.zhao@...el.com, 
	xiaoyao.li@...el.com, binbin.wu@...el.com, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On Thu, Nov 20, 2025, Rick Edgecombe wrote:
> +/*
> + * Return a page that can be used as TDX private memory
> + * and obtain TDX protections.

Wrap at ~80.

This comment is also misleading, arguably wrong.  Because from KVM's perspective,
these APIs are _never_ used to back TDX private memory.  They are used only for
control pages, which yeah, I suppose might be encrypted with the guest's private
key, but most readers will interpret "used as TDX private memory" to mean that
these are _the_ source of pages for guest private memory.

> + */
> +struct page *tdx_alloc_page(void)

And in a similar vein, given terminology in other places, maybe call these
tdx_{alloc,free}_control_page()?

> +{
> +	struct page *page;
> +
> +	page = alloc_page(GFP_KERNEL);

GFP_KERNEL_ACCOUNT, all of these allocations are tied to a VM.

> +	if (!page)
> +		return NULL;
> +
> +	if (tdx_pamt_get(page)) {
> +		__free_page(page);
> +		return NULL;
> +	}
> +
> +	return page;
> +}
> +EXPORT_SYMBOL_GPL(tdx_alloc_page);

Note, these can all now be EXPORT_SYMBOL_FOR_KVM.