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

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Message-ID: <f47df41b0a20062a74bd7f2fc1875b78632527eb.camel@intel.com>
Date: Thu, 29 Jan 2026 19:12:39 +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>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "Wu, Binbin" <binbin.wu@...el.com>,
	"kas@...nel.org" <kas@...nel.org>, "binbin.wu@...ux.intel.com"
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 Vishal" <vannapurve@...gle.com>, "Gao, Chao" <chao.gao@...el.com>,
	"bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On Thu, 2026-01-29 at 11:09 -0800, Sean Christopherson wrote:
> What you proposed is fundamentally quite different than what I'm
> proposing.  I'm not complaining about the union, I'm complaining
> about providing a helper to grab a pointer to the middle of a struct
> and then open coding memcpy() calls using that pointer.  I find that
> _extremely_ difficult to grok, because it does a poor job of
> capturing the intent (copy these values to this sequence of
> registers).
> 
> The decouple pointer+memcpy() approach also bleeds gory details about
> how PAMT pages are passed in multiple args throughout all SEAMCALL
> APIs that have such args.  I want the APIs to not have to care about
> the underlying mechanics of how PAMT pages are copied from an array
> to registers, e.g. so that readers of the code can focus on the
> semantics of the SEAMCALL and the pieces of logic that are
> unique to each SEAMCALL.
> 
> In other words, I see the necessity for a union as being a symptom of
> the flawed approach.

Ah ok, fair enough.