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

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Message-ID: <7e4dc2a683ce9cf5703399d233c71d4a3cc5ac53.camel@intel.com>
Date: Mon, 8 Dec 2025 20:27:31 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.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>, "Wu,
 Binbin" <binbin.wu@...el.com>, "kas@...nel.org" <kas@...nel.org>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "mingo@...hat.com"
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	<linux-kernel@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>,
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	"tglx@...utronix.de" <tglx@...utronix.de>, "Annapurve, Vishal"
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	<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 Mon, 2025-12-08 at 17:15 +0800, Yan Zhao wrote:
> On failure to allocate the 2nd page, instead of zeroing out the rest of the
> array and having the caller invoke free_pamt_array() to free the 1st page,
> could we free the 1st page here directly?
> 
> Upon alloc_pamt_array() error, the pages shouldn't have been passed to the TDX
> module, so there's no need to invoke tdx_quirk_reset_paddr() as in
> free_pamt_array(), right?

We don't want to optimize the error path. So I think less code is better than
making it slightly faster in an ultra rare case.

> 
> It's also somewhat strange to have the caller to invoke free_pamt_array() after
> alloc_pamt_array() fails.

Yea, I agree this code is a bit odd. Based on the discussion with Nikolay and
Dave, this can be less variable. It should get simplified as part of that.