linux-kernel - Re: [PATCH v19 039/130] KVM: TDX: initialize VM with TDX specific parameters

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Date: Fri, 17 May 2024 16:37:16 +0200
From: Juergen Gross <jgross@...e.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 isaku.yamahata@...el.com
Cc: 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>, Kai Huang <kai.huang@...el.com>,
 chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
 Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v19 039/130] KVM: TDX: initialize VM with TDX specific
 parameters

On 17.05.24 16:32, Kirill A. Shutemov wrote:
> On Mon, Feb 26, 2024 at 12:25:41AM -0800, isaku.yamahata@...el.com wrote:
>> @@ -725,6 +967,17 @@ static int __init tdx_module_setup(void)
>>   
>>   	tdx_info->nr_tdcs_pages = tdcs_base_size / PAGE_SIZE;
>>   
>> +	/*
>> +	 * Make TDH.VP.ENTER preserve RBP so that the stack unwinder
>> +	 * always work around it.  Query the feature.
>> +	 */
>> +	if (!(tdx_info->features0 & MD_FIELD_ID_FEATURES0_NO_RBP_MOD) &&
>> +	    !IS_ENABLED(CONFIG_FRAME_POINTER)) {
> 
> I think it supposed to be IS_ENABLED(CONFIG_FRAME_POINTER). "!" shouldn't
> be here.

No, I don't think so.

With CONFIG_FRAME_POINTER %rbp is being saved and restored, so there is no
problem in case the seamcall is clobbering it.

Juergen

> 
>> +		pr_err("Too old version of TDX module. Consider upgrade.\n");
>> +		ret = -EOPNOTSUPP;
>> +		goto error_out;
>> +	}
>> +
>>   	return 0;
>>   
> 

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