linux-kernel - Re: [PATCH v3 8/9] cxl/pci: Extend devm_cxl_port_enumerate_dports() to support restricted hosts (RCH)

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Date:   Fri, 11 Nov 2022 12:59:45 +0100
From:   Robert Richter <rrichter@....com>
To:     Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH v3 8/9] cxl/pci: Extend devm_cxl_port_enumerate_dports()
 to support restricted hosts (RCH)

On 09.11.22 11:40:58, Robert Richter wrote:

> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 667de4f125f6..a6b1a1501db3 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -48,6 +48,37 @@ static int pci_dev_add_dport(struct pci_dev *pdev, struct cxl_port *port,
>  	return 0;
>  }
>  
> +static int restricted_host_enumerate_dport(struct cxl_port *port,
> +					   struct pci_bus *bus)
> +{
> +	struct pci_dev *pdev;
> +	bool is_restricted_host;
> +	int rc;
> +
> +	/* Check CXL DVSEC of dev 0 func 0 */
> +	pdev = pci_get_slot(bus, PCI_DEVFN(0, 0));
> +
> +	is_restricted_host = pdev
> +		&& (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END)
> +		&& pci_find_dvsec_capability(pdev,
> +					PCI_DVSEC_VENDOR_ID_CXL,
> +					CXL_DVSEC_PCIE_DEVICE);
> +	if (is_restricted_host)
> +		rc = pci_dev_add_dport(pdev, port, CXL_RESOURCE_NONE);

See my comment in patch #6. This reads the port id from RCiEP's PCIe
cap, but instead the RCD UP RCRB should be used for this.
pci_dev_add_dport() needs to be updated to handle that.

-Robert

> +
> +	pci_dev_put(pdev);
> +
> +	if (!is_restricted_host)
> +		return 0;
> +
> +	dev_dbg(bus->bridge, "CXL restricted host found\n");
> +
> +	if (rc)
> +		return rc;
> +
> +	return 1;
> +}