linux-kernel - Re: [PATCH v2 3/7] x86/bugs: Exit early if return thunk is already set

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Message-ID: <4b60f99e-ae4d-49ae-b886-21e7377abe51@suse.com>
Date: Thu, 22 May 2025 13:26:16 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, x86@...nel.org
Cc: David Kaplan <david.kaplan@....com>, linux-kernel@...r.kernel.org,
 "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/7] x86/bugs: Exit early if return thunk is already
 set

On 5/22/25 13:22, Nikolay Borisov wrote:
> 
> 
> On 5/22/25 05:44, Pawan Gupta wrote:
>> ITS and retbleed can both set CDT return thunk. If the exact same return
>> thunk is already set, avoid the warning and exit early.
> 
> According to the code there is only a single call which sets the CDT 
> thunkand its in retbleed_apply_mitigation() if RETBLEED_MITIGATION_STUFF 
> is being used.
> 
> ITS OTOH only sets 'its_return_thunk'.
> 
> While the patch itself is not wrong, the description doesn't reflect the 
> current code?

So this is in preparation to allowing ITS to select the CDT, but this 
must be mentioned explicitly or simply squash this change into 'x86/its: 
Remove =stuff dependency on retbleed'

> 
>>
>> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> 
> 
>