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

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Message-ID: <20250522180338.uddvg6hm45soshpg@desk>
Date: Thu, 22 May 2025 11:03:38 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: x86@...nel.org, 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 Thu, May 22, 2025 at 01:26:16PM +0300, Nikolay Borisov wrote:
> 
> 
> 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'

Right, will update the commit message.