linux-kernel - Re: [PATCH v2 2/6] s390/uv: Retrieve UV secrets support

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Message-ID: <6ea3cfb4-47ab-478e-b5f0-0a02ec28b37d@linux.ibm.com>
Date: Mon, 7 Oct 2024 14:31:05 +0200
From: Janosch Frank <frankja@...ux.ibm.com>
To: Steffen Eiden <seiden@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Cc: Ingo Franzki <ifranzki@...ux.ibm.com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Christoph Schlameuss <schlameuss@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>
Subject: Re: [PATCH v2 2/6] s390/uv: Retrieve UV secrets support

On 10/2/24 6:05 PM, Steffen Eiden wrote:
> Provide a kernel API to retrieve secrets from the UV secret store.
> Add two new functions:
> * `uv_get_secret_metadata` - get metadata for a given secret identifier
> * `uv_retrieve_secret` - get the secret value for the secret index
> 
> With those two functions one can extract the secret for a given secret
> id, if the secret is retrievable.
> 
> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
> ---
>   arch/s390/include/asm/uv.h | 131 ++++++++++++++++++++++++++++++++++++-
>   arch/s390/kernel/uv.c      | 127 ++++++++++++++++++++++++++++++++++-
>   2 files changed, 256 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index 94ff58336e8e..aef333aaaef4 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -62,6 +62,7 @@
>   #define UVC_CMD_ADD_SECRET		0x1031
>   #define UVC_CMD_LIST_SECRETS		0x1033
>   #define UVC_CMD_LOCK_SECRETS		0x1034
> +#define UVC_CMD_RETR_SECRET		0x1035
>   
>   /* Bits in installed uv calls */
>   enum uv_cmds_inst {
> @@ -95,6 +96,7 @@ enum uv_cmds_inst {
>   	BIT_UVC_CMD_ADD_SECRET = 29,
>   	BIT_UVC_CMD_LIST_SECRETS = 30,
>   	BIT_UVC_CMD_LOCK_SECRETS = 31,
> +	BIT_UVC_CMD_RETR_SECRETS = 33,

One is SECRET and the other is SECRET_S_.
I know that you coded this according to spec, but sometimes we need to 
fix the spec. I've contacted the spec authors to fix it on their end if 
possible.

[...]

> + * Do the actual search for `uv_get_secret_metadata`
> + *
> + * Context: might sleep
> + */
> +static int find_secret(const u8 secret_id[UV_SECRET_ID_LEN],
> +		       struct uv_secret_list *list,
> +		       struct uv_secret_list_item_hdr *secret)
> +{
> +	u16 start_idx = 0;
> +	u16 list_rc;
> +	int ret;
> +
> +	do {
> +		uv_list_secrets((u8 *)list, start_idx, &list_rc, NULL);
> +		if (!(list_rc == UVC_RC_EXECUTED || list_rc == UVC_RC_MORE_DATA)) {

Inverting this conditional would get rid of 3 characters.
Did you chose to implement it like this on purpose?

> +			if (list_rc == UVC_RC_INV_CMD)
> +				return -ENODEV;
> +			else
> +				return -EIO;
> +		}
> +		ret = find_secret_in_page(secret_id, list, secret);
> +		if (ret == 0)
> +			return ret;
> +		start_idx = list->next_secret_idx;
> +	} while (list_rc == UVC_RC_MORE_DATA && start_idx < list->next_secret_idx);
> +
> +	return -ENOENT;