[PATCH V8 08/10] cxl/cdat: Introduce cxl_cdat_valid()

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

The CDAT data is protected by a checksum and should be the proper
length.

Introduce cxl_cdat_valid() to validate the data.  While at it check and
store the sequence number.

Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes from V6
	Change name to cxl_cdat_valid() as this validates all the CDAT
		data not just the header
	Add error and debug prints

Changes from V5
	New patch, split out
	Update cdat_hdr_valid()
		Remove revision and cs field parsing
			There is no point in these
		Add seq check and debug print.
---
 drivers/cxl/cdat.h |  2 ++
 drivers/cxl/pci.c  | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
index 4722b6bbbaf0..a7725d26f2d2 100644
--- a/drivers/cxl/cdat.h
+++ b/drivers/cxl/cdat.h
@@ -88,10 +88,12 @@
  *
  * @table: cache of CDAT table
  * @length: length of cached CDAT table
+ * @seq: Last read Sequence number of the CDAT table
  */
 struct cxl_cdat {
 	void *table;
 	size_t length;
+	u32 seq;
 };
 
 #endif /* !__CXL_CDAT_H__ */
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index aecb327911a0..d7952156dd02 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -781,6 +781,40 @@ static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
 	return 0;
 }
 
+static bool cxl_cdat_valid(struct device *dev, struct cxl_cdat *cdat)
+{
+	u32 *table = cdat->table;
+	u8 *data8 = cdat->table;
+	u32 length, seq;
+	u8 check;
+	int i;
+
+	length = FIELD_GET(CDAT_HEADER_DW0_LENGTH, table[0]);
+	if ((length < CDAT_HEADER_LENGTH_BYTES) || (length > cdat->length)) {
+		dev_err(dev, "Invalid length %u (%lu-%lu)\n", length,
+			CDAT_HEADER_LENGTH_BYTES, cdat->length);
+		return false;
+	}
+
+	for (check = 0, i = 0; i < length; i++)
+		check += data8[i];
+
+	dev_dbg(dev, "CDAT length %u CS %u\n", length, check);
+	if (check != 0) {
+		dev_err(dev, "Invalid checksum %u\n", check);
+		return false;
+	}
+
+	seq = FIELD_GET(CDAT_HEADER_DW3_SEQUENCE, table[3]);
+	/* Store the sequence for now. */
+	if (cdat->seq != seq) {
+		dev_info(dev, "CDAT seq change %x -> %x\n", cdat->seq, seq);
+		cdat->seq = seq;
+	}
+
+	return true;
+}
+
 #define CDAT_DOE_REQ(entry_handle)					\
 	(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE,			\
 		    CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) |		\
@@ -892,6 +926,8 @@ static int cxl_cdat_read_table(struct cxl_dev_state *cxlds,
 
 release_driver:
 	cxl_pci_doe_put_drv(doe_dev);
+	if (!rc && !cxl_cdat_valid(cxlds->dev, cdat))
+		return -EIO;
 	return rc;
 }
 
-- 
2.35.1