linux-kernel - Re: [PATCH v3 3/7] x86/bugs: Exit early if return thunk is already set

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Message-ID: <6b4a225e-c7ff-45e9-a2bb-62454927de57@suse.com>
Date: Fri, 23 May 2025 13:28:58 +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>, Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: [PATCH v3 3/7] x86/bugs: Exit early if return thunk is already
 set

On 5/23/25 04:21, Pawan Gupta wrote:
> When the exact same return thunk is already set, avoid the warning and exit
> early. This is to prepare for ITS to also set CDT return thunk independent
> of retbleed.

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>

> 
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> ---
>   arch/x86/kernel/cpu/bugs.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 94d0de3e61aec32b3b67c8d21f89a8c67b93dff3..354593065025fd7c5727e955d76523777b3da9ee 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -113,6 +113,9 @@ void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
>   
>   static void __init set_return_thunk(void *thunk)
>   {
> +	if (thunk == x86_return_thunk)
> +		return;
> +
>   	if (x86_return_thunk != __x86_return_thunk)
>   		pr_warn("x86/bugs: return thunk changed\n");
>   
>