linux-kernel - Re: [patch] percpu: Separate decrypted varaibles anytime encryption can be enabled

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Date:   Fri, 13 Dec 2019 15:37:07 -0800
From:   Dennis Zhou <dennis@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Brijesh Singh <brijesh.singh@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [patch] percpu: Separate decrypted varaibles anytime encryption
 can be enabled

Hi David,

On Fri, Dec 13, 2019 at 01:31:46PM -0800, David Rientjes wrote:
> From: Erdem Aktas <erdemaktas@...gle.com>
> 
> CONFIG_VIRTUALIZATION may not be enabled for memory encrypted guests.  If
> disabled, decrypted per-CPU variables may end up sharing the same page
> with variables that should be left encrypted.
> 
> Always separate per-CPU variables that should be decrypted into their own
> page anytime memory encryption can be enabled in the guest rather than
> rely on any other config option that may not be enabled.
> 
> Fixes: ac26963a1175 ("percpu: Introduce DEFINE_PER_CPU_DECRYPTED")
> Cc: stable@...r.kernel.org # 4.15+
> Signed-off-by: Erdem Aktas <erdemaktas@...gle.com>
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  include/linux/percpu-defs.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> --- a/include/linux/percpu-defs.h
> +++ b/include/linux/percpu-defs.h
> @@ -175,8 +175,7 @@
>   * Declaration/definition used for per-CPU variables that should be accessed
>   * as decrypted when memory encryption is enabled in the guest.
>   */
> -#if defined(CONFIG_VIRTUALIZATION) && defined(CONFIG_AMD_MEM_ENCRYPT)
> -
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
>  #define DECLARE_PER_CPU_DECRYPTED(type, name)				\
>  	DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
>  

Applied to for-5.6.

Thanks,
Dennis