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cxl/pci: Fix CDAT retrieval on big endian
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The CDAT exposed in sysfs differs between little endian and big endian
arches:  On big endian, every 4 bytes are byte-swapped.

PCI Configuration Space is little endian (PCI r3.0 sec 6.1).  Accessors
such as pci_read_config_dword() implicitly swap bytes on big endian.
That way, the macros in include/uapi/linux/pci_regs.h work regardless of
the arch's endianness.  For an example of implicit byte-swapping, see
ppc4xx_pciex_read_config(), which calls in_le32(), which uses lwbrx
(Load Word Byte-Reverse Indexed).

DOE Read/Write Data Mailbox Registers are unlike other registers in
Configuration Space in that they contain or receive a 4 byte portion of
an opaque byte stream (a "Data Object" per PCIe r6.0 sec 7.9.24.5f).
They need to be copied to or from the request/response buffer verbatim.
So amend pci_doe_send_req() and pci_doe_recv_resp() to undo the implicit
byte-swapping.

The CXL_DOE_TABLE_ACCESS_* and PCI_DOE_DATA_OBJECT_DISC_* macros assume
implicit byte-swapping.  Byte-swap requests after constructing them with
those macros and byte-swap responses before parsing them.

Change the request and response type to __le32 to avoid sparse warnings.
Per a request from Jonathan, replace sizeof(u32) with sizeof(__le32) for
consistency.

Fixes: c970060 ("cxl/port: Read CDAT table")
Tested-by: Ira Weiny <[email protected]>
Signed-off-by: Lukas Wunner <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Cc: [email protected] # v6.0+
Reviewed-by: Jonathan Cameron <[email protected]>
Link: https://lore.kernel.org/r/3051114102f41d19df3debbee123129118fc5e6d.1678543498.git.lukas@wunner.de
Signed-off-by: Dan Williams <[email protected]>
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@l1k @djbw
l1k authored and djbw committed Mar 21, 2023
1 parent e8d018d commit fbaa382
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Showing 3 changed files with 33 additions and 26 deletions.
26 changes: 13 additions & 13 deletions drivers/cxl/core/pci.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -462,7 +462,7 @@ static struct pci_doe_mb *find_cdat_doe(struct device *uport)
return NULL;
}

#define CDAT_DOE_REQ(entry_handle) \
#define CDAT_DOE_REQ(entry_handle) cpu_to_le32 \
(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE, \
CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) | \
FIELD_PREP(CXL_DOE_TABLE_ACCESS_TABLE_TYPE, \
Expand All @@ -475,8 +475,8 @@ static void cxl_doe_task_complete(struct pci_doe_task *task)
}

struct cdat_doe_task {
u32 request_pl;
u32 response_pl[32];
__le32 request_pl;
__le32 response_pl[32];
struct completion c;
struct pci_doe_task task;
};
Expand Down Expand Up @@ -510,10 +510,10 @@ static int cxl_cdat_get_length(struct device *dev,
return rc;
}
wait_for_completion(&t.c);
if (t.task.rv < sizeof(u32))
if (t.task.rv < sizeof(__le32))
return -EIO;

*length = t.response_pl[1];
*length = le32_to_cpu(t.response_pl[1]);
dev_dbg(dev, "CDAT length %zu\n", *length);

return 0;
Expand All @@ -524,13 +524,13 @@ static int cxl_cdat_read_table(struct device *dev,
struct cxl_cdat *cdat)
{
size_t length = cdat->length;
u32 *data = cdat->table;
__le32 *data = cdat->table;
int entry_handle = 0;

do {
DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(entry_handle), t);
size_t entry_dw;
u32 *entry;
__le32 *entry;
int rc;

rc = pci_doe_submit_task(cdat_doe, &t.task);
Expand All @@ -540,21 +540,21 @@ static int cxl_cdat_read_table(struct device *dev,
}
wait_for_completion(&t.c);
/* 1 DW header + 1 DW data min */
if (t.task.rv < (2 * sizeof(u32)))
if (t.task.rv < (2 * sizeof(__le32)))
return -EIO;

/* Get the CXL table access header entry handle */
entry_handle = FIELD_GET(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE,
t.response_pl[0]);
le32_to_cpu(t.response_pl[0]));
entry = t.response_pl + 1;
entry_dw = t.task.rv / sizeof(u32);
entry_dw = t.task.rv / sizeof(__le32);
/* Skip Header */
entry_dw -= 1;
entry_dw = min(length / sizeof(u32), entry_dw);
entry_dw = min(length / sizeof(__le32), entry_dw);
/* Prevent length < 1 DW from causing a buffer overflow */
if (entry_dw) {
memcpy(data, entry, entry_dw * sizeof(u32));
length -= entry_dw * sizeof(u32);
memcpy(data, entry, entry_dw * sizeof(__le32));
length -= entry_dw * sizeof(__le32);
data += entry_dw;
}
} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);
Expand Down
25 changes: 14 additions & 11 deletions drivers/pci/doe.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,7 @@ 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 + task->request_pl_sz / sizeof(__le32);
if (length > PCI_DOE_MAX_LENGTH)
return -EIO;
if (length == PCI_DOE_MAX_LENGTH)
Expand All @@ -141,9 +141,9 @@ 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));
for (i = 0; i < task->request_pl_sz / sizeof(u32); i++)
for (i = 0; i < task->request_pl_sz / sizeof(__le32); i++)
pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
task->request_pl[i]);
le32_to_cpu(task->request_pl[i]));

pci_doe_write_ctrl(doe_mb, PCI_DOE_CTRL_GO);

Expand Down Expand Up @@ -195,11 +195,11 @@ 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));
payload_length = min(length, task->response_pl_sz / sizeof(__le32));
/* Read the rest of the response payload */
for (i = 0; i < payload_length; i++) {
pci_read_config_dword(pdev, offset + PCI_DOE_READ,
&task->response_pl[i]);
pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
task->response_pl[i] = cpu_to_le32(val);
/* Prior to the last ack, ensure Data Object Ready */
if (i == (payload_length - 1) && !pci_doe_data_obj_ready(doe_mb))
return -EIO;
Expand All @@ -217,7 +217,7 @@ 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 min(length, task->response_pl_sz / sizeof(__le32)) * sizeof(__le32);
}

static void signal_task_complete(struct pci_doe_task *task, int rv)
Expand Down Expand Up @@ -317,14 +317,16 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
{
u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
*index);
__le32 request_pl_le = cpu_to_le32(request_pl);
__le32 response_pl_le;
u32 response_pl;
DECLARE_COMPLETION_ONSTACK(c);
struct pci_doe_task task = {
.prot.vid = PCI_VENDOR_ID_PCI_SIG,
.prot.type = PCI_DOE_PROTOCOL_DISCOVERY,
.request_pl = &request_pl,
.request_pl = &request_pl_le,
.request_pl_sz = sizeof(request_pl),
.response_pl = &response_pl,
.response_pl = &response_pl_le,
.response_pl_sz = sizeof(response_pl),
.complete = pci_doe_task_complete,
.private = &c,
Expand All @@ -340,6 +342,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
if (task.rv != sizeof(response_pl))
return -EIO;

response_pl = le32_to_cpu(response_pl_le);
*vid = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID, response_pl);
*protocol = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL,
response_pl);
Expand Down Expand Up @@ -533,8 +536,8 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
* 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))
if (task->request_pl_sz % sizeof(__le32) ||
task->response_pl_sz < sizeof(__le32))
return -EINVAL;

if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
Expand Down
8 changes: 6 additions & 2 deletions include/linux/pci-doe.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,10 @@ struct pci_doe_mb;
* @work: Used internally by the mailbox
* @doe_mb: Used internally by the mailbox
*
* Payloads are treated as opaque byte streams which are transmitted verbatim,
* without byte-swapping. If payloads contain little-endian register values,
* the caller is responsible for conversion with cpu_to_le32() / le32_to_cpu().
*
* The payload sizes and rv are specified in bytes with the following
* restrictions concerning the protocol.
*
Expand All @@ -45,9 +49,9 @@ struct pci_doe_mb;
*/
struct pci_doe_task {
struct pci_doe_protocol prot;
u32 *request_pl;
__le32 *request_pl;
size_t request_pl_sz;
u32 *response_pl;
__le32 *response_pl;
size_t response_pl_sz;
int rv;
void (*complete)(struct pci_doe_task *task);
Expand Down

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