diff mbox series

[v3,15/16] PCI/DOE: Relax restrictions on request and response size

Message ID fdb52e091b62b34c2036a61ae9ab8087dba4e4db.1676043318.git.lukas@wunner.de
State Superseded
Headers show
Series Collection of DOE material | expand

Commit Message

Lukas Wunner Feb. 10, 2023, 8:25 p.m. UTC 
An upcoming user of DOE is CMA (Component Measurement and Authentication,
PCIe r6.0 sec 6.31).

It builds on SPDM (Security Protocol and Data Model):
https://www.dmtf.org/dsp/DSP0274

SPDM message sizes are not always a multiple of dwords.  To transport
them over DOE without using bounce buffers, allow sending requests and
receiving responses whose final dword is only partially populated.

To be clear, PCIe r6.0 sec 6.30.1 specifies the Data Object Header 2
"Length" in dwords and pci_doe_send_req() and pci_doe_recv_resp()
read/write dwords.  So from a spec point of view, DOE is still specified
in dwords and allowing non-dword request/response buffers is merely for
the convenience of callers.

Tested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 Changes v2 -> v3:
 * Fix byte order of last dword on big endian arches (Ira)
 * Explain in commit message and kerneldoc that arbitrary-sized
   payloads are not stipulated by the spec, but merely for
   convenience of the caller (Bjorn, Jonathan)
 * Add code comment that "remainder" in pci_doe_recv_resp() signifies
   the number of data bytes in the last payload dword (Ira)

 drivers/pci/doe.c | 74 +++++++++++++++++++++++++++++++----------------
 1 file changed, 49 insertions(+), 25 deletions(-)

Comments

Li, Ming4 Feb. 15, 2023, 5:05 a.m. UTC | #1 
On 2/11/2023 4:25 AM, Lukas Wunner wrote:
> An upcoming user of DOE is CMA (Component Measurement and Authentication,
> PCIe r6.0 sec 6.31).
> 
> It builds on SPDM (Security Protocol and Data Model):
> https://www.dmtf.org/dsp/DSP0274
> 
> SPDM message sizes are not always a multiple of dwords.  To transport
> them over DOE without using bounce buffers, allow sending requests and
> receiving responses whose final dword is only partially populated.
> 
> To be clear, PCIe r6.0 sec 6.30.1 specifies the Data Object Header 2
> "Length" in dwords and pci_doe_send_req() and pci_doe_recv_resp()
> read/write dwords.  So from a spec point of view, DOE is still specified
> in dwords and allowing non-dword request/response buffers is merely for
> the convenience of callers.
> 
> Tested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  Changes v2 -> v3:
>  * Fix byte order of last dword on big endian arches (Ira)
>  * Explain in commit message and kerneldoc that arbitrary-sized
>    payloads are not stipulated by the spec, but merely for
>    convenience of the caller (Bjorn, Jonathan)
>  * Add code comment that "remainder" in pci_doe_recv_resp() signifies
>    the number of data bytes in the last payload dword (Ira)
> 
>  drivers/pci/doe.c | 74 +++++++++++++++++++++++++++++++----------------
>  1 file changed, 49 insertions(+), 25 deletions(-)
>

......

> +
> +	if (payload_length) {
> +		/* Read all payload dwords except the last */
> +		for (; i < payload_length - 1; i++) {
> +			pci_read_config_dword(pdev, offset + PCI_DOE_READ,
> +					      &val);
> +			task->response_pl[i] = cpu_to_le32(val);
> +			pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
> +		}
> +
> +		/* Read last payload dword */
>  		pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
> -		task->response_pl[i] = cpu_to_le32(val);
> +		cpu_to_le32s(&val);
> +		memcpy(&task->response_pl[i], &val, remainder);

This "Read last payload dword" seems like making sense only when remainder != sizeof(u32).
If remainder == sizeof(u32), it should be read in above reading loops.
But this implementation also looks good to me.

Reviewed-by: Ming Li <ming4.li@intel.com>

>  		/* Prior to the last ack, ensure Data Object Ready */
> -		if (i == (payload_length - 1) && !pci_doe_data_obj_ready(doe_mb))
> +		if (!pci_doe_data_obj_ready(doe_mb))
>  			return -EIO;
>  		pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
> +		i++;
>  	}
>  
>  	/* Flush excess length */
Lukas Wunner Feb. 15, 2023, 11:49 a.m. UTC | #2 
On Wed, Feb 15, 2023 at 01:05:20PM +0800, Li, Ming wrote:
> On 2/11/2023 4:25 AM, Lukas Wunner wrote:
> > An upcoming user of DOE is CMA (Component Measurement and Authentication,
> > PCIe r6.0 sec 6.31).
> > 
> > It builds on SPDM (Security Protocol and Data Model):
> > https://www.dmtf.org/dsp/DSP0274
> > 
> > SPDM message sizes are not always a multiple of dwords.  To transport
> > them over DOE without using bounce buffers, allow sending requests and
> > receiving responses whose final dword is only partially populated.
[...]
> > +	if (payload_length) {
> > +		/* Read all payload dwords except the last */
> > +		for (; i < payload_length - 1; i++) {
> > +			pci_read_config_dword(pdev, offset + PCI_DOE_READ,
> > +					      &val);
> > +			task->response_pl[i] = cpu_to_le32(val);
> > +			pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
> > +		}
> > +
> > +		/* Read last payload dword */
> >  		pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
> > -		task->response_pl[i] = cpu_to_le32(val);
> > +		cpu_to_le32s(&val);
> > +		memcpy(&task->response_pl[i], &val, remainder);
> 
> This "Read last payload dword" seems like making sense only when remainder != sizeof(u32).
> If remainder == sizeof(u32), it should be read in above reading loops.
> But this implementation also looks good to me.

The last payload dword requires special handling anyway because of
the Data Object Ready check (see quoted remainder of the function
below).

Up until now that special handling is done with an if-clause that
checks if the last loop iteration has been reached.

The support for non-dword responses adds more special handling
of the last payload dword, which is why I decided to go the full
distance and move handling of the last dword out of the loop.

Thanks,

Lukas

> >  		/* Prior to the last ack, ensure Data Object Ready */
> > -		if (i == (payload_length - 1) && !pci_doe_data_obj_ready(doe_mb))
> > +		if (!pci_doe_data_obj_ready(doe_mb))
> >  			return -EIO;
> >  		pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
> > +		i++;
> >  	}
> >  
> >  	/* Flush excess length */
diff mbox series

Patch

diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
index 15e5f9df1bba..14252f2fa955 100644
--- a/drivers/pci/doe.c
+++ b/drivers/pci/doe.c
@@ -76,13 +76,6 @@  struct pci_doe_protocol {
  * @private: Private data for the consumer
  * @work: Used internally by the mailbox
  * @doe_mb: Used internally by the mailbox
- *
- * The payload sizes and rv are specified in bytes with the following
- * restrictions concerning the protocol.
- *
- *	1) The request_pl_sz must be a multiple of double words (4 bytes)
- *	2) The response_pl_sz must be >= a single double word (4 bytes)
- *	3) rv is returned as bytes but it will be a multiple of double words
  */
 struct pci_doe_task {
 	struct pci_doe_protocol prot;
@@ -153,7 +146,7 @@  static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
 {
 	struct pci_dev *pdev = doe_mb->pdev;
 	int offset = doe_mb->cap_offset;
-	size_t length;
+	size_t length, remainder;
 	u32 val;
 	int i;
 
@@ -171,7 +164,7 @@  static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
 		return -EIO;
 
 	/* Length is 2 DW of header + length of payload in DW */
-	length = 2 + task->request_pl_sz / sizeof(u32);
+	length = 2 + DIV_ROUND_UP(task->request_pl_sz, sizeof(u32));
 	if (length > PCI_DOE_MAX_LENGTH)
 		return -EIO;
 	if (length == PCI_DOE_MAX_LENGTH)
@@ -184,10 +177,21 @@  static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
 	pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
 			       FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH,
 					  length));
+
+	/* Write payload */
 	for (i = 0; i < task->request_pl_sz / sizeof(u32); i++)
 		pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
 				       le32_to_cpu(task->request_pl[i]));
 
+	/* Write last payload dword */
+	remainder = task->request_pl_sz % sizeof(u32);
+	if (remainder) {
+		val = 0;
+		memcpy(&val, &task->request_pl[i], remainder);
+		le32_to_cpus(&val);
+		pci_write_config_dword(pdev, offset + PCI_DOE_WRITE, val);
+	}
+
 	pci_doe_write_ctrl(doe_mb, PCI_DOE_CTRL_GO);
 
 	return 0;
@@ -207,11 +211,11 @@  static bool pci_doe_data_obj_ready(struct pci_doe_mb *doe_mb)
 
 static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
 {
+	size_t length, payload_length, remainder, received;
 	struct pci_dev *pdev = doe_mb->pdev;
 	int offset = doe_mb->cap_offset;
-	size_t length, payload_length;
+	int i = 0;
 	u32 val;
-	int i;
 
 	/* Read the first dword to get the protocol */
 	pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
@@ -238,15 +242,38 @@  static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *tas
 
 	/* First 2 dwords have already been read */
 	length -= 2;
-	payload_length = min(length, task->response_pl_sz / sizeof(u32));
-	/* Read the rest of the response payload */
-	for (i = 0; i < payload_length; i++) {
+	received = task->response_pl_sz;
+	payload_length = DIV_ROUND_UP(task->response_pl_sz, sizeof(u32));
+	remainder = task->response_pl_sz % sizeof(u32);
+
+	/* remainder signifies number of data bytes in last payload dword */
+	if (!remainder)
+		remainder = sizeof(u32);
+
+	if (length < payload_length) {
+		received = length * sizeof(u32);
+		payload_length = length;
+		remainder = sizeof(u32);
+	}
+
+	if (payload_length) {
+		/* Read all payload dwords except the last */
+		for (; i < payload_length - 1; i++) {
+			pci_read_config_dword(pdev, offset + PCI_DOE_READ,
+					      &val);
+			task->response_pl[i] = cpu_to_le32(val);
+			pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
+		}
+
+		/* Read last payload dword */
 		pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
-		task->response_pl[i] = cpu_to_le32(val);
+		cpu_to_le32s(&val);
+		memcpy(&task->response_pl[i], &val, remainder);
 		/* Prior to the last ack, ensure Data Object Ready */
-		if (i == (payload_length - 1) && !pci_doe_data_obj_ready(doe_mb))
+		if (!pci_doe_data_obj_ready(doe_mb))
 			return -EIO;
 		pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
+		i++;
 	}
 
 	/* Flush excess length */
@@ -260,7 +287,7 @@  static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *tas
 	if (FIELD_GET(PCI_DOE_STATUS_ERROR, val))
 		return -EIO;
 
-	return min(length, task->response_pl_sz / sizeof(u32)) * sizeof(u32);
+	return received;
 }
 
 static void signal_task_complete(struct pci_doe_task *task, int rv)
@@ -561,14 +588,6 @@  static int pci_doe_submit_task(struct pci_doe_mb *doe_mb,
 	if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
 		return -EINVAL;
 
-	/*
-	 * DOE requests must be a whole number of DW and the response needs to
-	 * be big enough for at least 1 DW
-	 */
-	if (task->request_pl_sz % sizeof(u32) ||
-	    task->response_pl_sz < sizeof(u32))
-		return -EINVAL;
-
 	if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
 		return -EIO;
 
@@ -596,6 +615,11 @@  static int pci_doe_submit_task(struct pci_doe_mb *doe_mb,
  * without byte-swapping.  If payloads contain little-endian register values,
  * the caller is responsible for conversion with cpu_to_le32() / le32_to_cpu().
  *
+ * For convenience, arbitrary payload sizes are allowed even though PCIe r6.0
+ * sec 6.30.1 specifies the Data Object Header 2 "Length" in dwords.  The last
+ * (partial) dword is copied with byte granularity and padded with zeroes if
+ * necessary.  Callers are thus relieved from using dword-sized bounce buffers.
+ *
  * RETURNS: Length of received response or negative errno.
  * Received data in excess of @response_sz is discarded.
  * The length may be smaller than @response_sz and the caller