Re: [PATCH RFC 05/15] tools/testing/cxl: Add "Set Passphrase" opcode support

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Fri, 15 Jul 2022 14:09:01 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> Add support to emulate a CXL mem device supporting the "Set Passphrase"
> operation. The operation supports setting of either a user or a master
> passphrase.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Hi Dave,

A few comments inline.

Thanks,

Jonathan

> ---
>  tools/testing/cxl/test/mem.c |   76 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 76 insertions(+)
> 
> diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> index 337e5a099d31..796f4f7b5e3d 100644
> --- a/tools/testing/cxl/test/mem.c
> +++ b/tools/testing/cxl/test/mem.c
> @@ -12,8 +12,14 @@
>  struct mock_mdev_data {
>  	void *lsa;
>  	u32 security_state;
> +	u8 user_pass[NVDIMM_PASSPHRASE_LEN];
> +	u8 master_pass[NVDIMM_PASSPHRASE_LEN];
> +	int user_limit;
> +	int master_limit;
>  };
>  
> +#define PASS_TRY_LIMIT 3
> +
>  #define LSA_SIZE SZ_128K
>  #define EFFECT(x) (1U << x)
>  
> @@ -162,6 +168,73 @@ static int mock_get_security_state(struct cxl_dev_state *cxlds,
>  	return 0;
>  }
>  
> +static int mock_set_passphrase(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd)
> +{
> +	struct mock_mdev_data *mdata = dev_get_drvdata(cxlds->dev);
> +	struct cxl_set_pass *set_pass;
> +
> +	if (cmd->size_in != sizeof(*set_pass)) {
> +		cmd->return_code = CXL_MBOX_CMD_RC_INPUT;

If it makes sense to set I think this should be invalid payload length.

> +		return -EINVAL;
> +	}
> +
> +	if (cmd->size_out != 0) {
> +		cmd->return_code = CXL_MBOX_CMD_RC_INPUT;

As before. I'm not 100% sure this is actually an error from
device point of view (it fills the buffer whatever).  Obviously
it's an error in the software so return -EINVAL makes sense.


> +		return -EINVAL;
> +	}
> +
> +	if (mdata->security_state & CXL_PMEM_SEC_STATE_FROZEN) {
> +		cmd->return_code = CXL_MBOX_CMD_RC_SECURITY;
> +		return -ENXIO;
> +	}
> +
> +	set_pass = cmd->payload_in;
> +	switch (set_pass->type) {
> +	case CXL_PMEM_SEC_PASS_MASTER:
> +		if (mdata->security_state & CXL_PMEM_SEC_STATE_MASTER_PLIMIT) {
> +			cmd->return_code = CXL_MBOX_CMD_RC_SECURITY;
> +			return -ENXIO;
> +		}
> +		/*
> +		 * CXL spec v2.0 8.2.9.5.6.2, The master pasphrase shall only be set in
> +		 * the security disabled state when the user passphrase is not set.
> +		 */
> +		if (mdata->security_state & CXL_PMEM_SEC_STATE_USER_PASS_SET) {
> +			cmd->return_code = CXL_MBOX_CMD_RC_SECURITY;
> +			return -ENXIO;
> +		}
> +		if (mdata->security_state & CXL_PMEM_SEC_STATE_MASTER_PASS_SET &&
> +		    memcmp(mdata->master_pass, set_pass->old_pass, NVDIMM_PASSPHRASE_LEN)) {
> +			if (++mdata->master_limit == PASS_TRY_LIMIT)
> +				mdata->security_state |= CXL_PMEM_SEC_STATE_MASTER_PLIMIT;
> +			cmd->return_code = CXL_MBOX_CMD_RC_PASSPHRASE;
> +			return -ENXIO;
> +		}
> +		memcpy(mdata->master_pass, set_pass->new_pass, NVDIMM_PASSPHRASE_LEN);
> +		break;
> +
> +	case CXL_PMEM_SEC_PASS_USER:
> +		if (mdata->security_state & CXL_PMEM_SEC_STATE_USER_PLIMIT) {
> +			cmd->return_code = CXL_MBOX_CMD_RC_SECURITY;
> +			return -ENXIO;
> +		}
> +		if (mdata->security_state & CXL_PMEM_SEC_STATE_USER_PASS_SET &&
> +		    memcmp(mdata->user_pass, set_pass->old_pass, NVDIMM_PASSPHRASE_LEN)) {
> +			if (++mdata->user_limit == PASS_TRY_LIMIT)
> +				mdata->security_state |= CXL_PMEM_SEC_STATE_USER_PLIMIT;
> +			cmd->return_code = CXL_MBOX_CMD_RC_PASSPHRASE;
> +			return -ENXIO;
> +		}
> +		memcpy(mdata->user_pass, set_pass->new_pass, NVDIMM_PASSPHRASE_LEN);
> +		break;
> +
> +	default:
> +		cmd->return_code = CXL_MBOX_CMD_RC_INPUT;
> +		return -EINVAL;
> +	}

I would directly return rather than break; above as reduces the code someone following
either case needs to look at.  + saves a whole 1 line of code ;)

> +	return 0;
> +}
> +
>  static int mock_get_lsa(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd)
>  {
>  	struct cxl_mbox_get_lsa *get_lsa = cmd->payload_in;
> @@ -257,6 +330,9 @@ static int cxl_mock_mbox_send(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *
>  	case CXL_MBOX_OP_GET_SECURITY_STATE:
>  		rc = mock_get_security_state(cxlds, cmd);
>  		break;
> +	case CXL_MBOX_OP_SET_PASSPHRASE:
> +		rc = mock_set_passphrase(cxlds, cmd);
> +		break;
>  	default:
>  		break;
>  	}
> 
>