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Subject[PATCH v3 5/9] cxl/pci: Only register RCDs with device 0, function 0 as CXL memory device
Date
The Device 0, Function 0 DVSEC controls the CXL functionality of the
entire device. Add a check to prevent registration of any other PCI
device on the bus as a CXL memory device.

Signed-off-by: Robert Richter <rrichter@amd.com>
---
drivers/cxl/pci.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index faeb5d9d7a7a..cc4f206f24b3 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -428,11 +428,26 @@ static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
}
}

+static int check_restricted_device(struct pci_dev *pdev, u16 pcie_dvsec)
+{
+ if (pci_pcie_type(pdev) != PCI_EXP_TYPE_RC_END)
+ return 0; /* no RCD */
+
+ if (pdev->devfn == PCI_DEVFN(0, 0) && pcie_dvsec)
+ return 0; /* ok */
+
+ dev_warn(&pdev->dev, "Skipping RCD: devfn=0x%02x dvsec=%u\n",
+ pdev->devfn, pcie_dvsec);
+
+ return -ENODEV;
+}
+
static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
struct cxl_register_map map;
struct cxl_memdev *cxlmd;
struct cxl_dev_state *cxlds;
+ u16 pcie_dvsec;
int rc;

/*
@@ -442,6 +457,13 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
BUILD_BUG_ON(offsetof(struct cxl_regs, memdev) !=
offsetof(struct cxl_regs, device_regs.memdev));

+ pcie_dvsec = pci_find_dvsec_capability(
+ pdev, PCI_DVSEC_VENDOR_ID_CXL, CXL_DVSEC_PCIE_DEVICE);
+
+ rc = check_restricted_device(pdev, pcie_dvsec);
+ if (rc)
+ return rc;
+
rc = pcim_enable_device(pdev);
if (rc)
return rc;
@@ -451,8 +473,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
return PTR_ERR(cxlds);

cxlds->serial = pci_get_dsn(pdev);
- cxlds->cxl_dvsec = pci_find_dvsec_capability(
- pdev, PCI_DVSEC_VENDOR_ID_CXL, CXL_DVSEC_PCIE_DEVICE);
+ cxlds->cxl_dvsec = pcie_dvsec;
if (!cxlds->cxl_dvsec)
dev_warn(&pdev->dev,
"Device DVSEC not present, skip CXL.mem init\n");
--
2.30.2
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