Re: [PATCH v8 01/16] PCI/CXL: Introduce PCIe helper function pcie_is_cxl()

From: Ira Weiny
Date: Thu Mar 27 2025 - 11:11:45 EST


Terry Bowman wrote:
> CXL and AER drivers need the ability to identify CXL devices.
>
> Add set_pcie_cxl() with logic checking for CXL Flexbus DVSEC presence. The
> CXL Flexbus DVSEC presence is used because it is required for all the CXL
> PCIe devices.[1]
>
> Add boolean 'struct pci_dev::is_cxl' with the purpose to cache the CXL
> Flexbus presence.
>
> Add function pcie_is_cxl() to return 'struct pci_dev::is_cxl'.
>
> [1] CXL 3.1 Spec, 8.1.1 PCIe Designated Vendor-Specific Extended
> Capability (DVSEC) ID Assignment, Table 8-2
>
> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
> ---
> drivers/pci/pci.c | 5 +++++
> drivers/pci/probe.c | 10 ++++++++++
> include/linux/pci.h | 3 +++
> include/uapi/linux/pci_regs.h | 8 +++++++-
> 4 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 869d204a70a3..a1d75f40017e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5032,6 +5032,11 @@ static u16 cxl_port_dvsec(struct pci_dev *dev)
> PCI_DVSEC_CXL_PORT);
> }
>
> +inline bool pcie_is_cxl(struct pci_dev *pci_dev)
> +{
> + return pci_dev->is_cxl;
> +}

Shouldn't this just be a static inline in include/linux/pci.h?

> +
> static bool cxl_sbr_masked(struct pci_dev *dev)
> {
> u16 dvsec, reg;

[snip]

> @@ -741,6 +742,8 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
> return false;
> }
>
> +bool pcie_is_cxl(struct pci_dev *pci_dev);
> +
> #define for_each_pci_bridge(dev, bus) \
> list_for_each_entry(dev, &bus->devices, bus_list) \
> if (!pci_is_bridge(dev)) {} else
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 3445c4970e4d..7ccb3b2fcc38 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1208,9 +1208,15 @@
> #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00ff0000
> #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xff000000
>
> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
> +/* Compute Express Link (CXL r3.1, sec 8.1)
r3.2

> + *
> + * Note that CXL DVSEC id 3 and 7 to be ignored when the CXL link state
> + * is "disconnected" (CXL r3.1, sec 9.12.3). Re-enumerate these
r3.2
Same sections. :-D

With changes:

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

Ira

[snip]