linux-kernel - Re: [PATCH V2 01/11] cxl/pci: Add generic MSI-X/MSI irq support

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Message-ID: <e896ca47-6192-190f-ad63-6a294c0c246e@intel.com>
Date:   Thu, 1 Dec 2022 11:37:54 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     ira.weiny@...el.com, Dan Williams <dan.j.williams@...el.com>
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Subject: Re: [PATCH V2 01/11] cxl/pci: Add generic MSI-X/MSI irq support



On 11/30/2022 5:27 PM, ira.weiny@...el.com wrote:
> From: Davidlohr Bueso <dave@...olabs.net>
> 
> Currently the only CXL features targeted for irq support require their
> message numbers to be within the first 16 entries.  The device may
> however support less than 16 entries depending on the support it
> provides.
> 
> Attempt to allocate these 16 irq vectors.  If the device supports less
> then the PCI infrastructure will allocate that number.  Store the number
> of vectors actually allocated in the device state for later use
> by individual functions.
> 
> Upon successful allocation, users can plug in their respective isr at
> any point thereafter, for example, if the irq setup is not done in the
> PCI driver, such as the case of the CXL-PMU.
> 
> Cc: Bjorn Helgaas <helgaas@...nel.org>
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Davidlohr Bueso <dave@...olabs.net>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> 
> ---
> Changes from V1:
> 	Jonathan
> 		pci_alloc_irq_vectors() cleans up the vectors automatically
> 		use msi_enabled rather than nr_irq_vecs
> 
> Changes from Ira
> 	Remove reviews
> 	Allocate up to a static 16 vectors.
> 	Change cover letter
> ---
>   drivers/cxl/cxlmem.h |  3 +++
>   drivers/cxl/cxlpci.h |  6 ++++++
>   drivers/cxl/pci.c    | 23 +++++++++++++++++++++++
>   3 files changed, 32 insertions(+)
> 
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 88e3a8e54b6a..cd35f43fedd4 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -211,6 +211,7 @@ struct cxl_endpoint_dvsec_info {
>    * @info: Cached DVSEC information about the device.
>    * @serial: PCIe Device Serial Number
>    * @doe_mbs: PCI DOE mailbox array
> + * @msi_enabled: MSI-X/MSI has been enabled
>    * @mbox_send: @dev specific transport for transmitting mailbox commands
>    *
>    * See section 8.2.9.5.2 Capacity Configuration and Label Storage for
> @@ -247,6 +248,8 @@ struct cxl_dev_state {
>   
>   	struct xarray doe_mbs;
>   
> +	bool msi_enabled;
> +
>   	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
>   };
>   
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index eec597dbe763..b7f4e2f417d3 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -53,6 +53,12 @@
>   #define	    CXL_DVSEC_REG_LOCATOR_BLOCK_ID_MASK			GENMASK(15, 8)
>   #define     CXL_DVSEC_REG_LOCATOR_BLOCK_OFF_LOW_MASK		GENMASK(31, 16)
>   
> +/*
> + * NOTE: Currently all the functions which are enabled for CXL require their
> + * vectors to be in the first 16.  Use this as the max.
> + */
> +#define CXL_PCI_REQUIRED_VECTORS 16
> +
>   /* Register Block Identifier (RBI) */
>   enum cxl_regloc_type {
>   	CXL_REGLOC_RBI_EMPTY = 0,
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index faeb5d9d7a7a..8f86f85d89c7 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -428,6 +428,27 @@ static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
>   	}
>   }
>   
> +static void cxl_pci_alloc_irq_vectors(struct cxl_dev_state *cxlds)
> +{
> +	struct device *dev = cxlds->dev;
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	int nvecs;
> +
> +	/*
> +	 * NOTE: pci_alloc_irq_vectors() handles calling pci_free_irq_vectors()
> +	 * automatically despite not being called pcim_*.  See
> +	 * pci_setup_msi_context().
> +	 */
> +	nvecs = pci_alloc_irq_vectors(pdev, 1, CXL_PCI_REQUIRED_VECTORS,
> +				   PCI_IRQ_MSIX | PCI_IRQ_MSI);
> +	if (nvecs < 0) {
> +		dev_dbg(dev, "Failed to alloc irq vectors; use polling instead.\n");
> +		return;
> +	}
> +
> +	cxlds->msi_enabled = true;
> +}
> +
>   static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   {
>   	struct cxl_register_map map;
> @@ -494,6 +515,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   	if (rc)
>   		return rc;
>   
> +	cxl_pci_alloc_irq_vectors(cxlds);
> +
>   	cxlmd = devm_cxl_add_memdev(cxlds);
>   	if (IS_ERR(cxlmd))
>   		return PTR_ERR(cxlmd);