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Date: Fri, 17 Nov 2023 21:15:36 +0100
From: Robert Richter <rrichter@....com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Ira Weiny <ira.weiny@...el.com>,
Davidlohr Bueso <dave@...olabs.net>,
Jonathan Cameron <jonathan.cameron@...wei.com>,
Dave Jiang <dave.jiang@...el.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
Fan Ni <nifan.cxl@...il.com>, Lukas Wunner <lukas@...ner.de>
Subject: [PATCH] cxl/pci: Get rid of pointer arithmetic reading CDAT table
On 17.11.23 21:09:18, Robert Richter wrote:
> I will send an on-top patch for 6.8 that reworks that code area to
> remove the pointer arithmetic.
Here it is:
>From 13787f72c20b8c54754ae86015d982307eae0397 Mon Sep 17 00:00:00 2001
From: Robert Richter <rrichter@....com>
Subject: [PATCH] cxl/pci: Get rid of pointer arithmetic reading CDAT table
Reading the CDAT table using DOE requires a Table Access Response
Header in addition to the CDAT entry. In current implementation this
has caused offsets with sizeof(__le32) to the actual buffers. This led
to hardly readable code and even bugs (see fix of devm_kfree() in
read_cdat_data()).
Rework code to avoid calculations with sizeof(__le32). Introduce
struct cdat_doe for this which contains the Table Access Response
Header and a variable payload size for various data structures
afterwards to access the CDAT table and its CDAT Data Structures
without recalculating buffer offsets.
Cc: Lukas Wunner <lukas@...ner.de>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Fan Ni <nifan.cxl@...il.com>
Signed-off-by: Robert Richter <rrichter@....com>
---
drivers/cxl/core/pci.c | 80 ++++++++++++++++++++----------------------
drivers/cxl/cxlpci.h | 19 ++++++++++
2 files changed, 57 insertions(+), 42 deletions(-)
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 5aaa0b36c42a..f900740c6dea 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -517,14 +517,14 @@ EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
FIELD_PREP(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE, (entry_handle)))
static int cxl_cdat_get_length(struct device *dev,
- struct pci_doe_mb *cdat_doe,
+ struct pci_doe_mb *doe_mb,
size_t *length)
{
__le32 request = CDAT_DOE_REQ(0);
__le32 response[2];
int rc;
- rc = pci_doe(cdat_doe, PCI_DVSEC_VENDOR_ID_CXL,
+ rc = pci_doe(doe_mb, PCI_DVSEC_VENDOR_ID_CXL,
CXL_DOE_PROTOCOL_TABLE_ACCESS,
&request, sizeof(request),
&response, sizeof(response));
@@ -542,56 +542,54 @@ static int cxl_cdat_get_length(struct device *dev,
}
static int cxl_cdat_read_table(struct device *dev,
- struct pci_doe_mb *cdat_doe,
- void *cdat_table, size_t *cdat_length)
+ struct pci_doe_mb *doe_mb,
+ struct cdat_doe *doe, size_t *length)
{
- size_t length = *cdat_length + sizeof(__le32);
- __le32 *data = cdat_table;
+ size_t received, remaining = *length;
int entry_handle = 0;
__le32 saved_dw = 0;
do {
__le32 request = CDAT_DOE_REQ(entry_handle);
- struct cdat_entry_header *entry;
- size_t entry_dw;
int rc;
- rc = pci_doe(cdat_doe, PCI_DVSEC_VENDOR_ID_CXL,
+ rc = pci_doe(doe_mb, PCI_DVSEC_VENDOR_ID_CXL,
CXL_DOE_PROTOCOL_TABLE_ACCESS,
&request, sizeof(request),
- data, length);
+ doe, sizeof(*doe) + remaining);
if (rc < 0) {
dev_err(dev, "DOE failed: %d", rc);
return rc;
}
- /* 1 DW Table Access Response Header + CDAT entry */
- entry = (struct cdat_entry_header *)(data + 1);
+ if (rc < sizeof(*doe))
+ return -EIO;
+
+ received = rc - sizeof(*doe);
+
if ((entry_handle == 0 &&
- rc != sizeof(__le32) + sizeof(struct cdat_header)) ||
+ received != sizeof(doe->header[0])) ||
(entry_handle > 0 &&
- (rc < sizeof(__le32) + sizeof(*entry) ||
- rc != sizeof(__le32) + le16_to_cpu(entry->length))))
+ (received < sizeof(doe->entry[0]) ||
+ received != le16_to_cpu(doe->entry->length))))
return -EIO;
/* Get the CXL table access header entry handle */
entry_handle = FIELD_GET(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE,
- le32_to_cpu(data[0]));
- entry_dw = rc / sizeof(__le32);
- /* Skip Header */
- entry_dw -= 1;
+ le32_to_cpu(doe->doe_header));
+
/*
* Table Access Response Header overwrote the last DW of
* previous entry, so restore that DW
*/
- *data = saved_dw;
- length -= entry_dw * sizeof(__le32);
- data += entry_dw;
- saved_dw = *data;
+ doe->doe_header = saved_dw;
+ remaining -= received;
+ doe = (void *)doe + received;
+ saved_dw = doe->doe_header;
} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);
/* Length in CDAT header may exceed concatenation of CDAT entries */
- *cdat_length -= length - sizeof(__le32);
+ *length -= remaining;
return 0;
}
@@ -616,11 +614,11 @@ void read_cdat_data(struct cxl_port *port)
{
struct device *uport = port->uport_dev;
struct device *dev = &port->dev;
- struct pci_doe_mb *cdat_doe;
+ struct pci_doe_mb *doe_mb;
struct pci_dev *pdev = NULL;
struct cxl_memdev *cxlmd;
- size_t cdat_length;
- void *cdat_table, *cdat_buf;
+ struct cdat_doe *doe;
+ size_t length;
int rc;
if (is_cxl_memdev(uport)) {
@@ -637,40 +635,38 @@ void read_cdat_data(struct cxl_port *port)
if (!pdev)
return;
- cdat_doe = pci_find_doe_mailbox(pdev, PCI_DVSEC_VENDOR_ID_CXL,
- CXL_DOE_PROTOCOL_TABLE_ACCESS);
- if (!cdat_doe) {
+ doe_mb = pci_find_doe_mailbox(pdev, PCI_DVSEC_VENDOR_ID_CXL,
+ CXL_DOE_PROTOCOL_TABLE_ACCESS);
+ if (!doe_mb) {
dev_dbg(dev, "No CDAT mailbox\n");
return;
}
port->cdat_available = true;
- if (cxl_cdat_get_length(dev, cdat_doe, &cdat_length)) {
+ if (cxl_cdat_get_length(dev, doe_mb, &length)) {
dev_dbg(dev, "No CDAT length\n");
return;
}
- cdat_buf = devm_kzalloc(dev, cdat_length + sizeof(__le32),
- GFP_KERNEL);
- if (!cdat_buf)
- return;
+ doe = devm_kzalloc(dev, sizeof(*doe) + length, GFP_KERNEL);
+ if (!doe)
+ goto err;
- rc = cxl_cdat_read_table(dev, cdat_doe, cdat_buf, &cdat_length);
+ rc = cxl_cdat_read_table(dev, doe_mb, doe, &length);
if (rc)
goto err;
- cdat_table = cdat_buf + sizeof(__le32);
- if (cdat_checksum(cdat_table, cdat_length))
+ if (cdat_checksum(doe->table, length))
goto err;
- port->cdat.table = cdat_table;
- port->cdat.length = cdat_length;
- return;
+ port->cdat.table = doe->table;
+ port->cdat.length = length;
+ return;
err:
/* Don't leave table data allocated on error */
- devm_kfree(dev, cdat_buf);
+ devm_kfree(dev, doe);
dev_err(dev, "Failed to read/validate CDAT.\n");
}
EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);
diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
index 0fa4799ea316..d12ed9d8dec1 100644
--- a/drivers/cxl/cxlpci.h
+++ b/drivers/cxl/cxlpci.h
@@ -85,6 +85,25 @@ struct cdat_entry_header {
__le16 length;
} __packed;
+/*
+ * Response contains the CDAT only response header of the DOE. The
+ * response payload is a CDAT structure (either CDAT header or entry),
+ * it may also mark the beginning of the CDAT table.
+ *
+ * Spec refs:
+ *
+ * CXL 3.1 Table 8-14: Read Entry Response
+ * CDAT Specification 1.03: 2 CDAT Data Structures
+ */
+struct cdat_doe {
+ __le32 doe_header;
+ union {
+ u8 table[0];
+ struct cdat_header header[0];
+ struct cdat_entry_header entry[0];
+ };
+} __packed;
+
int devm_cxl_port_enumerate_dports(struct cxl_port *port);
struct cxl_dev_state;
int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
--
2.39.2
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