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

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Message-ID: <1840e1dba9e25c9d913926b28f6d7569c74f9d92.camel@intel.com>
Date: Fri, 16 Jan 2026 23:25:44 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "Huang, Kai" <kai.huang@...el.com>, "Li,
 Xiaoyao" <xiaoyao.li@...el.com>, "Hansen, Dave" <dave.hansen@...el.com>,
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	<x86@...nel.org>
Subject: Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On Fri, 2026-01-16 at 15:17 -0800, Sean Christopherson wrote:
> 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.

Maybe just drop "private" and call it TDX 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()?

True, that is the only use today, but also there is nothing control page
specific about the functions themselves. I'm ok changing it, but I'm not sure it
helps that much.

> 
> > +{
> > +	struct page *page;
> > +
> > +	page = alloc_page(GFP_KERNEL);
> 
> GFP_KERNEL_ACCOUNT, all of these allocations are tied to a VM.

Yes, thanks.

> 
> > +	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.

Sure.