[PATCH net-next 0/3] psp: add crypt-offset and spi-threshold attributes

[PATCH net-next 0/3] psp: add crypt-offset and spi-threshold attributes

[Akhilesh Samineni]

This series introduces two new configurable per-device attributes to
the PSP (PSP Security Protocol) subsystem: crypt-offset and spi-threshold.

crypt-offset (Crypt Offset)
----------------------------------
The crypt-offset attribute specifies the byte offset within a packet from
which encryption begins. A non-zero value allows a fixed-size portion of
the packet header to remain in plaintext, which is useful where
intermediate network nodes need to inspect a well-known header before the
encrypted region. The default value is 0, meaning encryption starts
immediately after the PSP header.

spi-threshold (SPI Threshold)
-------------------------------
SPI values are allocated monotonically from a 32-bit per-device space.
The spi-threshold attribute lets userspace configure the SPI value at
which rotation should be triggered before the space is exhausted.

A named constant PSP_SPI_THRESHOLD_DEFAULT (~90% of 0x7FFFFFFF) is
introduced in include/net/psp/types.h as the single authoritative
definition, used by both the PSP core (psp_main.c) and the netdevsim
driver (psp.c). This avoids scattering the magic value across drivers.

A follow-up series will add netlink notification support to alert
subscribed listeners when the configured spi-threshold is reached,
enabling timely SPI rotation.

Akhilesh Samineni (3):
  psp: add crypt-offset and spi-threshold get/set attributes
  netdevsim: psp: handle the new crypt-offset and spi-threshold get/set operations
  selftests: net: psp: add crypt-offset and spi-threshold test cases

 Documentation/netlink/specs/psp.yaml       | 13 +++++++++
 drivers/net/netdevsim/netdevsim.h          |  2 ++
 drivers/net/netdevsim/psp.c                |  6 ++++
 include/net/psp/types.h                    |  7 +++++
 include/uapi/linux/psp.h                   |  2 ++
 net/psp/psp-nl-gen.c                       |  6 ++--
 net/psp/psp_main.c                         |  3 ++
 net/psp/psp_nl.c                           | 27 +++++++++++++++---
 tools/testing/selftests/drivers/net/psp.py | 32 +++++++++++++++++++++++
 9 files changed, 92 insertions(+), 6 deletions(-)

-- 
2.45.4

[PATCH net-next 1/3] psp: add crypt-offset and spi-threshold get/set attributes

[Akhilesh Samineni]

crypt-offset (Crypt Offset)
----------------------------------
The crypt-offset attribute specifies the byte offset within a packet
from which encryption begins. This is a per-device attribute that
allows a portion of the packet header to remain in plaintext while
the rest of the payload is encrypted. This is useful in scenarios
where intermediate nodes need to inspect or process a fixed-size
header before the encrypted payload.

The default value is 0, meaning encryption starts from the beginning
of the payload following the PSP header.

spi-threshold (SPI Threshold)
------------------------------
The SPI (Security Parameter Index) is a 32-bit per-device identifier
used to distinguish security associations. As SPI values are allocated
monotonically, a threshold is needed to trigger timely SPI rotation
before the space is exhausted.

The spi-threshold attribute allows userspace to configure the value at
which an SPI rotation should be initiated. The default is set to
PSP_SPI_THRESHOLD_DEFAULT (~90% of 0x7FFFFFFF), providing a comfortable
margin to perform rotation without racing to exhaustion.

NOTE: A follow-up series will add notification support to alert
subscribed users when the configured spi-threshold is reached, enabling
timely SPI rotation.

Signed-off-by: Akhilesh Samineni <akhilesh.samineni@broadcom.com>
Reviewed-by: Kiran Kella <kiran.kella@broadcom.com>
Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
---
 Documentation/netlink/specs/psp.yaml | 13 +++++++++++++
 include/net/psp/types.h              |  7 +++++++
 include/uapi/linux/psp.h             |  2 ++
 net/psp/psp-nl-gen.c                 |  6 ++++--
 net/psp/psp_main.c                   |  3 +++
 net/psp/psp_nl.c                     | 27 +++++++++++++++++++++++----
 6 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/Documentation/netlink/specs/psp.yaml b/Documentation/netlink/specs/psp.yaml
index f3a57782d2cf..b22869be91cf 100644
--- a/Documentation/netlink/specs/psp.yaml
+++ b/Documentation/netlink/specs/psp.yaml
@@ -38,6 +38,15 @@ attribute-sets:
         type: u32
         enum: version
         enum-as-flags: true
+      -
+        name: crypt-offset
+        doc: The offset from the end of the PSP header to the start of the encrypted payload.
+        type: u8
+      -
+        name: spi-threshold
+        doc: Threshold for the SPI to trigger notification to the user for appropriate rotate action.
+        type: u32
+
   -
     name: assoc
     attributes:
@@ -170,6 +179,8 @@ operations:
             - ifindex
             - psp-versions-cap
             - psp-versions-ena
+            - crypt-offset
+            - spi-threshold
         pre: psp-device-get-locked
         post: psp-device-unlock
       dump:
@@ -193,6 +204,8 @@ operations:
           attributes:
             - id
             - psp-versions-ena
+            - crypt-offset
+            - spi-threshold
         reply:
           attributes: []
         pre: psp-device-get-locked
diff --git a/include/net/psp/types.h b/include/net/psp/types.h
index 25a9096d4e7d..875f7822557f 100644
--- a/include/net/psp/types.h
+++ b/include/net/psp/types.h
@@ -25,6 +25,9 @@ struct psphdr {
 #define PSP_SPI_KEY_ID		GENMASK(30, 0)
 #define PSP_SPI_KEY_PHASE	BIT(31)
 
+/* Default SPI threshold: ~90% of max SPI (0x7FFFFFFF) to allow rotation before exhaustion */
+#define PSP_SPI_THRESHOLD_DEFAULT	0x73333333
+
 #define PSPHDR_CRYPT_OFFSET	GENMASK(5, 0)
 
 #define PSPHDR_VERFL_SAMPLE	BIT(7)
@@ -38,9 +41,13 @@ struct psphdr {
 /**
  * struct psp_dev_config - PSP device configuration
  * @versions: PSP versions enabled on the device
+ * @crypt_offset: crypto offset configured on the device
+ * @spi_threshold: SPI threshold value on the device
  */
 struct psp_dev_config {
 	u32 versions;
+	u8 crypt_offset;
+	u32 spi_threshold;
 };
 
 /**
diff --git a/include/uapi/linux/psp.h b/include/uapi/linux/psp.h
index a3a336488dc3..bb390159dc72 100644
--- a/include/uapi/linux/psp.h
+++ b/include/uapi/linux/psp.h
@@ -22,6 +22,8 @@ enum {
 	PSP_A_DEV_IFINDEX,
 	PSP_A_DEV_PSP_VERSIONS_CAP,
 	PSP_A_DEV_PSP_VERSIONS_ENA,
+	PSP_A_DEV_CRYPT_OFFSET,
+	PSP_A_DEV_SPI_THRESHOLD,
 
 	__PSP_A_DEV_MAX,
 	PSP_A_DEV_MAX = (__PSP_A_DEV_MAX - 1)
diff --git a/net/psp/psp-nl-gen.c b/net/psp/psp-nl-gen.c
index 22a48d0fa378..e50b8b80955c 100644
--- a/net/psp/psp-nl-gen.c
+++ b/net/psp/psp-nl-gen.c
@@ -23,9 +23,11 @@ static const struct nla_policy psp_dev_get_nl_policy[PSP_A_DEV_ID + 1] = {
 };
 
 /* PSP_CMD_DEV_SET - do */
-static const struct nla_policy psp_dev_set_nl_policy[PSP_A_DEV_PSP_VERSIONS_ENA + 1] = {
+static const struct nla_policy psp_dev_set_nl_policy[PSP_A_DEV_SPI_THRESHOLD + 1] = {
 	[PSP_A_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
 	[PSP_A_DEV_PSP_VERSIONS_ENA] = NLA_POLICY_MASK(NLA_U32, 0xf),
+	[PSP_A_DEV_CRYPT_OFFSET] = { .type = NLA_U8, },
+	[PSP_A_DEV_SPI_THRESHOLD] = { .type = NLA_U32, },
 };
 
 /* PSP_CMD_KEY_ROTATE - do */
@@ -75,7 +77,7 @@ static const struct genl_split_ops psp_nl_ops[] = {
 		.doit		= psp_nl_dev_set_doit,
 		.post_doit	= psp_device_unlock,
 		.policy		= psp_dev_set_nl_policy,
-		.maxattr	= PSP_A_DEV_PSP_VERSIONS_ENA,
+		.maxattr	= PSP_A_DEV_SPI_THRESHOLD,
 		.flags		= GENL_CMD_CAP_DO,
 	},
 	{
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index 9508b6c38003..536ee44db09d 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -79,6 +79,9 @@ psp_dev_create(struct net_device *netdev,
 	INIT_LIST_HEAD(&psd->stale_assocs);
 	refcount_set(&psd->refcnt, 1);
 
+	/* ~90% of 0x7FFFFFFF; allows SPI rotation well before space is exhausted */
+	psd->config.spi_threshold = PSP_SPI_THRESHOLD_DEFAULT;
+
 	mutex_lock(&psp_devs_lock);
 	err = xa_alloc_cyclic(&psp_devs, &psd->id, psd, xa_limit_16b,
 			      &last_id, GFP_KERNEL);
diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index 6afd7707ec12..fbb77460a24b 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -101,7 +101,9 @@ psp_nl_dev_fill(struct psp_dev *psd, struct sk_buff *rsp,
 	if (nla_put_u32(rsp, PSP_A_DEV_ID, psd->id) ||
 	    nla_put_u32(rsp, PSP_A_DEV_IFINDEX, psd->main_netdev->ifindex) ||
 	    nla_put_u32(rsp, PSP_A_DEV_PSP_VERSIONS_CAP, psd->caps->versions) ||
-	    nla_put_u32(rsp, PSP_A_DEV_PSP_VERSIONS_ENA, psd->config.versions))
+	    nla_put_u32(rsp, PSP_A_DEV_PSP_VERSIONS_ENA, psd->config.versions) ||
+	    nla_put_u8(rsp, PSP_A_DEV_CRYPT_OFFSET, psd->config.crypt_offset) ||
+	    nla_put_u32(rsp, PSP_A_DEV_SPI_THRESHOLD, psd->config.spi_threshold))
 		goto err_cancel_msg;
 
 	genlmsg_end(rsp, hdr);
@@ -193,6 +195,13 @@ int psp_nl_dev_set_doit(struct sk_buff *skb, struct genl_info *info)
 
 	memcpy(&new_config, &psd->config, sizeof(new_config));
 
+	if (!info->attrs[PSP_A_DEV_PSP_VERSIONS_ENA] &&
+	    !info->attrs[PSP_A_DEV_CRYPT_OFFSET] &&
+	    !info->attrs[PSP_A_DEV_SPI_THRESHOLD]) {
+		NL_SET_ERR_MSG(info->extack, "No settings present");
+		return -EINVAL;
+	}
+
 	if (info->attrs[PSP_A_DEV_PSP_VERSIONS_ENA]) {
 		new_config.versions =
 			nla_get_u32(info->attrs[PSP_A_DEV_PSP_VERSIONS_ENA]);
@@ -200,9 +209,19 @@ int psp_nl_dev_set_doit(struct sk_buff *skb, struct genl_info *info)
 			NL_SET_ERR_MSG(info->extack, "Requested PSP versions not supported by the device");
 			return -EINVAL;
 		}
-	} else {
-		NL_SET_ERR_MSG(info->extack, "No settings present");
-		return -EINVAL;
+	}
+
+	if (info->attrs[PSP_A_DEV_CRYPT_OFFSET])
+		new_config.crypt_offset =
+			nla_get_u8(info->attrs[PSP_A_DEV_CRYPT_OFFSET]);
+
+	if (info->attrs[PSP_A_DEV_SPI_THRESHOLD]) {
+		new_config.spi_threshold =
+			nla_get_u32(info->attrs[PSP_A_DEV_SPI_THRESHOLD]);
+		if (new_config.spi_threshold & PSP_SPI_KEY_PHASE) {
+			NL_SET_ERR_MSG(info->extack, "SPI threshold must not have bit 31 set");
+			return -EINVAL;
+		}
 	}
 
 	rsp = psp_nl_reply_new(info);
-- 
2.45.4

[PATCH net-next 2/3] netdevsim: psp: handle the new crypt-offset and spi-threshold get/set operations

[Akhilesh Samineni]

Implement the crypt-offset and spi-threshold get/set in netdevsim PSP.

Signed-off-by: Akhilesh Samineni <akhilesh.samineni@broadcom.com>
Reviewed-by: Kiran Kella <kiran.kella@broadcom.com>
Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
---
 drivers/net/netdevsim/netdevsim.h | 2 ++
 drivers/net/netdevsim/psp.c       | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index c904e14f6b3f..3ad7d42391c0 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -117,6 +117,8 @@ struct netdevsim {
 		struct psp_dev *dev;
 		u32 spi;
 		u32 assoc_cnt;
+		u8  crypt_offset;
+		u32 spi_threshold;
 	} psp;
 
 	struct nsim_bus_dev *nsim_bus_dev;
diff --git a/drivers/net/netdevsim/psp.c b/drivers/net/netdevsim/psp.c
index 0b4d717253b0..9098edf00c5c 100644
--- a/drivers/net/netdevsim/psp.c
+++ b/drivers/net/netdevsim/psp.c
@@ -122,6 +122,11 @@ static int
 nsim_psp_set_config(struct psp_dev *psd, struct psp_dev_config *conf,
 		    struct netlink_ext_ack *extack)
 {
+	struct netdevsim *ns = psd->drv_priv;
+
+	ns->psp.crypt_offset = conf->crypt_offset;
+	ns->psp.spi_threshold = conf->spi_threshold;
+
 	return 0;
 }
 
@@ -249,6 +254,7 @@ int nsim_psp_init(struct netdevsim *ns)
 	if (err)
 		return err;
 
+	ns->psp.spi_threshold = PSP_SPI_THRESHOLD_DEFAULT;
 	debugfs_create_file("psp_rereg", 0200, ddir, ns, &nsim_psp_rereg_fops);
 	return 0;
 }
-- 
2.45.4

[PATCH net-next 3/3] selftests: net: psp: add crypt-offset and spi-threshold test cases

[Akhilesh Samineni]

Add test cases to set and get crypt-offset and spi-threshold attributes,
verifying both the applied value and the restored prior value.

Signed-off-by: Akhilesh Samineni <akhilesh.samineni@broadcom.com>
Reviewed-by: Kiran Kella <kiran.kella@broadcom.com>
Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
---
 tools/testing/selftests/drivers/net/psp.py | 32 ++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/psp.py b/tools/testing/selftests/drivers/net/psp.py
index 864d9fce1094..9253aab29ded 100755
--- a/tools/testing/selftests/drivers/net/psp.py
+++ b/tools/testing/selftests/drivers/net/psp.py
@@ -171,6 +171,38 @@ def dev_get_device_bad(cfg):
     ksft_true(raised)
 
 
+def dev_set_crypt_offset(cfg):
+    """ Set and get the crypt-offset """
+    _init_psp_dev(cfg)
+
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    orig = dev['crypt-offset']
+    cfg.pspnl.dev_set({"id": cfg.psp_dev_id,
+                       "crypt-offset": 5})
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    ksft_eq(dev['crypt-offset'], 5)
+    cfg.pspnl.dev_set({"id": cfg.psp_dev_id,
+                       "crypt-offset": orig})
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    ksft_eq(dev['crypt-offset'], orig)
+
+
+def dev_set_spi_threshold(cfg):
+    """ Set and get the spi-threshold """
+    _init_psp_dev(cfg)
+
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    orig = dev['spi-threshold']
+    cfg.pspnl.dev_set({"id": cfg.psp_dev_id,
+                       "spi-threshold": 10})
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    ksft_eq(dev['spi-threshold'], 10)
+    cfg.pspnl.dev_set({"id": cfg.psp_dev_id,
+                       "spi-threshold": orig})
+    dev = cfg.pspnl.dev_get({'id': cfg.psp_dev_id})
+    ksft_eq(dev['spi-threshold'], orig)
+
+
 def dev_rotate(cfg):
     """ Test key rotation """
     _init_psp_dev(cfg)
-- 
2.45.4

Re: [PATCH net-next 0/3] psp: add crypt-offset and spi-threshold attributes

[Jakub Kicinski]

On Mon,  6 Apr 2026 15:23:02 -0700 Akhilesh Samineni wrote:
> This series introduces two new configurable per-device attributes to
> the PSP (PSP Security Protocol) subsystem: crypt-offset and spi-threshold.

Please read this document:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
-- 
pw-bot: cr

Re: [PATCH net-next 0/3] psp: add crypt-offset and spi-threshold attributes

[Akhilesh Samineni]

[-- Attachment #1: Type: text/plain, Size: 577 bytes --]

On Tue, Apr 7, 2026 at 6:44 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Mon,  6 Apr 2026 15:23:02 -0700 Akhilesh Samineni wrote:
> > This series introduces two new configurable per-device attributes to
> > the PSP (PSP Security Protocol) subsystem: crypt-offset and spi-threshold.
>
> Please read this document:
> https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
> --

Thank you for the link. I have reviewed the netdev process documentation.
I’ve ensured my patches pass checkpatch and include the correct maintainers.

> pw-bot: cr

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4211 bytes --]

Re: [PATCH net-next 0/3] psp: add crypt-offset and spi-threshold attributes

[Daniel Zahka]

On 4/7/26 11:39 AM, Akhilesh Samineni wrote:
> On Tue, Apr 7, 2026 at 6:44 AM Jakub Kicinski <kuba@kernel.org> wrote:
>> On Mon,  6 Apr 2026 15:23:02 -0700 Akhilesh Samineni wrote:
>>> This series introduces two new configurable per-device attributes to
>>> the PSP (PSP Security Protocol) subsystem: crypt-offset and spi-threshold.
>> Please read this document:
>> https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
>> --
> Thank you for the link. I have reviewed the netdev process documentation.
> I’ve ensured my patches pass checkpatch and include the correct maintainers.


Hi Akhilesh. There's a sentence in the netdevsim section of that 
document that is problematic for the series as it is currently: 
"netdevsim in itself is not considered a use case/user. You must also 
implement the new APIs in a real driver."