linux-kernel - Re: [PATCHv2 04/12] x86/virt/tdx: Add tdx_alloc/free

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Message-ID: <aFyYcT+BzbRkcCBT@intel.com>
Date: Thu, 26 Jun 2025 08:46:41 +0800
From: Chao Gao <chao.gao@...el.com>
To: Dave Hansen <dave.hansen@...el.com>
CC: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	<pbonzini@...hat.com>, <seanjc@...gle.com>, <dave.hansen@...ux.intel.com>,
	<rick.p.edgecombe@...el.com>, <isaku.yamahata@...el.com>,
	<kai.huang@...el.com>, <yan.y.zhao@...el.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <kvm@...r.kernel.org>, <x86@...nel.org>,
	<linux-coco@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 04/12] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On Wed, Jun 25, 2025 at 01:09:05PM -0700, Dave Hansen wrote:
>On 6/9/25 19:36, Chao Gao wrote:
>>> +static int tdx_alloc_pamt_pages(struct list_head *pamt_pages)
>>> +{
>>> +	for (int i = 0; i < tdx_nr_pamt_pages(); i++) {
>>> +		struct page *page = alloc_page(GFP_KERNEL);
>>> +		if (!page)
>>> +			goto fail;
>> 
>> this goto isn't needed. it is used only once. so we can just free the pages and
>> return -ENOMEM here.
>
><shrug>
>
>There's no rule saying that gotos need to be used more than once. It's
>idiomatic kernel C to use a goto as an error landing site. In fact, I
>*prefer* this because it lets me read the main, non-error-case flow
>through the function. Then, at my leisure, I can review the error handling.
>
>This is also, IMNHO, less error-prone to someone adding code and doing a
>plain return without freeing the pages.
>
>Third, the goto keeps the indentation down.
>
>So, the suggestion here is well intended, but I think it's flawed in
>multiple ways. If you write your code this way (free of one-use gotos),
>I won't complain too much. But if you suggest other folks get rid of the
>gotos, I'm not super happy.
>
>So, Kirill, do it whatever way you want.
>
>But, Chao, please don't keep suggesting things like this at least in
>junk I've got to merge.

Sure. I am still trying to develop a sense of good code. Thank you, Dave, for
correcting me and the detailed explanation.