linux-kernel - Re: [PATCH v19 008/130] x86/tdx: Warning with 32bit build shift-count-overflow

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Date: Wed, 6 Mar 2024 10:35:43 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Isaku Yamahata <isaku.yamahata@...ux.intel.com>, "Kirill A. Shutemov"
	<kirill.shutemov@...ux.intel.com>
CC: <isaku.yamahata@...el.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <isaku.yamahata@...il.com>, Paolo Bonzini
	<pbonzini@...hat.com>, <erdemaktas@...gle.com>, Sean Christopherson
	<seanjc@...gle.com>, Sagi Shahar <sagis@...gle.com>, <chen.bo@...el.com>,
	<hang.yuan@...el.com>, <tina.zhang@...el.com>
Subject: Re: [PATCH v19 008/130] x86/tdx: Warning with 32bit build
 shift-count-overflow



On 5/03/2024 9:12 pm, Isaku Yamahata wrote:
> On Fri, Mar 01, 2024 at 01:36:43PM +0200,
> "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> 
>> On Thu, Feb 29, 2024 at 11:49:13AM +1300, Huang, Kai wrote:
>>>
>>>
>>> On 26/02/2024 9:25 pm, isaku.yamahata@...el.com wrote:
>>>> From: Isaku Yamahata <isaku.yamahata@...el.com>
>>>>
>>>> This patch fixes the following warnings.
>>>>
>>>>      In file included from arch/x86/kernel/asm-offsets.c:22:
>>>>      arch/x86/include/asm/tdx.h:92:87: warning: shift count >= width of type [-Wshift-count-overflow]
>>>>      arch/x86/include/asm/tdx.h:20:21: note: expanded from macro 'TDX_ERROR'
>>>>      #define TDX_ERROR                       _BITUL(63)
>>>>
>>>>                                              ^~~~~~~~~~
>>>>
>>
>> I think you trim the warning message. I don't see the actual user of the
>> define. Define itself will not generate the warning. You need to actually
>> use it outside of preprocessor. I don't understand who would use it in
>> 32-bit code. Maybe fixing it this way masking other issue.
>>
>> That said, I don't object the change itself. We just need to understand
>> the context more.
> 
> v18 used it as stub function. v19 dropped it as the stub was not needed.

Sorry I literally don't understand what you are talking about here.

Please just clarify (at least):

  - Does this problem exist in upstream code?
  - If it does, what is the root cause, and how to reproduce?