linux-kernel - Re: [PATCH] crypto: ccp - Don't initialize SEV support without the SEV feature

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Date:   Thu, 4 Mar 2021 18:04:25 -0600
From:   Brijesh Singh <brijesh.singh@....com>
To:     Tom Lendacky <thomas.lendacky@....com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     brijesh.singh@....com, Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        John Allen <john.allen@....com>
Subject: Re: [PATCH] crypto: ccp - Don't initialize SEV support without the
 SEV feature


On 3/3/21 4:31 PM, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@....com>
>
> If SEV has been disabled (e.g. through BIOS), the driver probe will still
> issue SEV firmware commands. The SEV INIT firmware command will return an
> error in this situation, but the error code is a general error code that
> doesn't highlight the exact reason.
>
> Add a check for X86_FEATURE_SEV in sev_dev_init() and emit a meaningful
> message and skip attempting to initialize the SEV firmware if the feature
> is not enabled. Since building the SEV code is dependent on X86_64, adding
> the check won't cause any build problems.
>
> Cc: John Allen <john.allen@....com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>


Reviewed-By: Brijesh Singh <brijesh.singh@....com>

> ---
>  drivers/crypto/ccp/sev-dev.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 476113e12489..b9fc8d7aca73 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -21,6 +21,7 @@
>  #include <linux/ccp.h>
>  #include <linux/firmware.h>
>  #include <linux/gfp.h>
> +#include <linux/cpufeature.h>
>  
>  #include <asm/smp.h>
>  
> @@ -971,6 +972,11 @@ int sev_dev_init(struct psp_device *psp)
>  	struct sev_device *sev;
>  	int ret = -ENOMEM;
>  
> +	if (!boot_cpu_has(X86_FEATURE_SEV)) {
> +		dev_info_once(dev, "SEV: memory encryption not enabled by BIOS\n");
> +		return 0;
> +	}
> +
>  	sev = devm_kzalloc(dev, sizeof(*sev), GFP_KERNEL);
>  	if (!sev)
>  		goto e_err;