[PATCH 2/2] cxl/doe: Request exclusive DOE access

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

The PCIE Data Object Exchange (DOE) mailbox is a protocol run over
configuration cycles.  It assumes one initiator at a time.  While the
kernel has control of the mailbox user space writes could interfere with
the kernel access.

Mark DOE mailbox config space exclusive when iterated by the CXL driver.

Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
---
 drivers/cxl/pci.c             | 5 +++++
 include/uapi/linux/pci_regs.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index faeb5d9d7a7a..5b833eb91543 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -418,6 +418,11 @@ static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
 			continue;
 		}
 
+		if (!pci_request_config_region_exclusive(pdev, off,
+							 PCI_DOE_CAP_SIZE,
+							 dev_name(dev)))
+			pci_err(pdev, "Failed to exclude DOE registers\n");
+
 		if (xa_insert(&cxlds->doe_mbs, off, doe_mb, GFP_KERNEL)) {
 			dev_err(dev, "xa_insert failed to insert MB @ %x\n",
 				off);
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 57b8e2ffb1dd..f2396bcd09cc 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -1119,6 +1119,7 @@
 #define  PCI_DOE_STATUS_DATA_OBJECT_READY	0x80000000  /* Data Object Ready */
 #define PCI_DOE_WRITE		0x10    /* DOE Write Data Mailbox Register */
 #define PCI_DOE_READ		0x14    /* DOE Read Data Mailbox Register */
+#define PCI_DOE_CAP_SIZE	(0x14 + 4)	/* Size of this register block */
 
 /* DOE Data Object - note not actually registers */
 #define PCI_DOE_DATA_OBJECT_HEADER_1_VID		0x0000ffff
-- 
2.37.2