linux-kernel - Re: [PATCH] crypto: ccp: Load the firmware twice when SEV API version

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Date:   Thu, 4 Aug 2022 09:59:44 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Jarkko Sakkinen <jarkko@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Jarkko Sakkinen <jarkko@...fian.com>,
        Harald Hoyer <harald@...fian.com>,
        Brijesh Singh <brijesh.singh@....com>,
        John Allen <john.allen@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "open list:AMD CRYPTOGRAPHIC COPROCESSOR (CCP) DRIVER - SE..." 
        <linux-crypto@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccp: Load the firmware twice when SEV API version
 < 1.43

On 8/3/22 20:02, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <jarkko@...fian.com>
> 
> SEV-SNP does not initialize to a legit state, unless the firmware is
> loaded twice, when SEP API version < 1.43, and the firmware is updated
> to a later version. Because of this user space needs to work around
> this with "rmmod && modprobe" combo. Fix this by implementing the
> workaround to the driver.
> 
> Reported-by: Harald Hoyer <harald@...fian.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@...fian.com>
> ---
>   drivers/crypto/ccp/sev-dev.c | 22 +++++++++++++++++++---
>   1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 799b476fc3e8..f2abb7439dde 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c

> @@ -1274,6 +1285,7 @@ void sev_pci_init(void)
>   {
>   	struct sev_device *sev = psp_master->sev_data;
>   	int error, rc;
> +	int i;
>   
>   	if (!sev)
>   		return;
> @@ -1283,9 +1295,13 @@ void sev_pci_init(void)
>   	if (sev_get_api_version())
>   		goto err;
>   
> -	if (sev_version_greater_or_equal(0, 15) &&
> -	    sev_update_firmware(sev->dev) == 0)
> -		sev_get_api_version();
> +	/*
> +	 * SEV-SNP does not work properly before loading the FW twice in the API
> +	 * versions older than SEV 1.43.
> +	 */
> +	for (i = 0; i < sev_version_greater_or_equal(0, 15) + sev_version_less(1, 43); i++)
> +		if (sev_update_firmware(sev->dev) == 0)
> +			sev_get_api_version();

I prefer to have this logic in the sev_update_firmware() function.

And while the loop is correct, it isn't obvious. Something in
sev_update_firmware() that just does:

	ret = sev_do_cmd(SEV_CMD_DOWNLOAD_FIRMWARE, data, &error);

	if (!ret && sev_version_greater_or_equal(0, 15) && sev_version_less(1, 43))
		ret = sev_do_cmd(SEV_CMD_DOWNLOAD_FIRMWARE, data, &error);

And place a comment before the second command that references the reason
for the second download.

Thanks,
Tom

>