linux-kernel - Re: [PATCH v2 07/25] x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled

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Date:   Fri, 12 Mar 2021 13:44:58 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     kvm@...r.kernel.org, linux-sgx@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, jarkko@...nel.org, luto@...nel.org,
        dave.hansen@...el.com, rick.p.edgecombe@...el.com,
        haitao.huang@...el.com, pbonzini@...hat.com, bp@...en8.de,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH v2 07/25] x86/sgx: Initialize virtual EPC driver even
 when SGX driver is disabled

On Tue, Mar 09, 2021, Kai Huang wrote:
> Modify sgx_init() to always try to initialize the virtual EPC driver,
> even if the SGX driver is disabled.  The SGX driver might be disabled
> if SGX Launch Control is in locked mode, or not supported in the
> hardware at all.  This allows (non-Linux) guests that support non-LC
> configurations to use SGX.
> 
> Acked-by: Dave Hansen <dave.hansen@...el.com>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>  arch/x86/kernel/cpu/sgx/main.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 44fe91a5bfb3..8c922e68274d 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -712,7 +712,15 @@ static int __init sgx_init(void)
>  		goto err_page_cache;
>  	}
>  
> -	ret = sgx_drv_init();
> +	/*
> +	 * Always try to initialize the native *and* KVM drivers.
> +	 * The KVM driver is less picky than the native one and
> +	 * can function if the native one is not supported on the
> +	 * current system or fails to initialize.
> +	 *
> +	 * Error out only if both fail to initialize.
> +	 */
> +	ret = !!sgx_drv_init() & !!sgx_vepc_init();

I love this code.

Reviewed-by: Sean Christopherson <seanjc@...gle.com>

>  	if (ret)
>  		goto err_kthread;
>  
> -- 
> 2.29.2
>