linux-kernel - Re: [PATCH v3 02/26] x86/virt/tdx: Use %# prefix for hex values in SEAMCALL error messages

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Message-ID: <aXn+AHBfbbeGzxWO@intel.com>
Date: Wed, 28 Jan 2026 20:16:00 +0800
From: Chao Gao <chao.gao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
CC: <linux-coco@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, <x86@...nel.org>, <reinette.chatre@...el.com>,
	<ira.weiny@...el.com>, <kai.huang@...el.com>, <dan.j.williams@...el.com>,
	<yilun.xu@...ux.intel.com>, <sagis@...gle.com>, <vannapurve@...gle.com>,
	<paulmck@...nel.org>, <nik.borisov@...e.com>, <zhenzhong.duan@...el.com>,
	<seanjc@...gle.com>, <rick.p.edgecombe@...el.com>, <kas@...nel.org>,
	<dave.hansen@...ux.intel.com>, <vishal.l.verma@...el.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 02/26] x86/virt/tdx: Use %# prefix for hex values in
 SEAMCALL error messages

On Wed, Jan 28, 2026 at 09:34:03AM +0800, Binbin Wu wrote:
>
>
>On 1/23/2026 10:55 PM, Chao Gao wrote:
>> "%#" format specifier automatically adds the "0x" prefix and has one less
>> character than "0x%".
>> 
>> For conciseness, replace "0x%" with "%#" when printing hexadecimal values
>> in SEAMCALL error messages.
>> 
>> Suggested-by: Dan Williams <dan.j.williams@...el.com>
>> Signed-off-by: Chao Gao <chao.gao@...el.com>
>
>Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
>
>> ---
>> "0x%" is also used to print TDMR ranges. I didn't convert them to reduce
>> code churn, but if they should be converted for consistency, I'm happy
>> to do that.
>
>Generally, is there any preference for coding in Linux kernel about
>"0x%" VS. "%#"? Or developers just make their own choices?

There seems to be no clear guidance on "0x%x" vs. "%#x".

If anyone has strong objections to this change, I can definitely drop it. I
included this patch because Dan suggested it during his review, though I'm not
sure how strongly he feels about it.

I searched lore and found the example below where "%#x" is preferred in another
subsystem:

https://lore.kernel.org/all/20251202231352.GF1712166@ZenIV/