linux-kernel - Re: [PATCH 3/4] x86/kexec(): Reset TDX private memory on platforms with TDX erratum

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Date: Thu, 1 Feb 2024 22:22:18 +0800
From: "Huang, Kai" <kai.huang@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Dave Hansen
	<dave.hansen@...el.com>
CC: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <tglx@...utronix.de>,
	<bp@...en8.de>, <mingo@...hat.com>, <hpa@...or.com>, <luto@...nel.org>,
	<peterz@...radead.org>, <thomas.lendacky@....com>, <chao.gao@...el.com>,
	<bhe@...hat.com>, <nik.borisov@...e.com>, <pbonzini@...hat.com>
Subject: Re: [PATCH 3/4] x86/kexec(): Reset TDX private memory on platforms
 with TDX erratum



On 1/02/2024 6:03 am, Kirill A. Shutemov wrote:
> On Wed, Jan 31, 2024 at 01:21:39PM -0800, Dave Hansen wrote:
>>>   #ifdef CONFIG_KEXEC_JUMP
>>>   	if (image->preserve_context)
>>>   		save_processor_state();
>>> +	else
>>> +		tdx_reset_memory();
>>> +#else
>>> +	tdx_reset_memory();
>>>   #endif
>>
>> Wow, that's awfully hard to read.  I really wish folks' gag reflex would
>> kick in when they see stuff like this to get them to spend an additional
>> 15 seconds to turn this into:
>>
>> 	if (IS_ENABLED(CONFIG_KEXEC_JUMP) && image->preserve_context)
>> 		save_processor_state();
>> 	else
>> 		tdx_reset_memory();
> 
> save_processor_state() is declared under CONFIG_PM_SLEEP, so I guess your
> variant might break build in some cases without updated suspend.h.

I tried.  If I turn off both SUSPEND and HIBERNATION in the Kconfig I 
got build error：

arch/x86/kernel/machine_kexec_64.c:325:17: error: implicit declaration 
of function ‘save_processor_state’ [-Werror=implicit-function-declaration]
   325 |                 save_processor_state();
       |                 ^~~~~~~~~~~~~~~~~~~~