Re: [PATCH V8 04/10] cxl/pci: Create auxiliary devices for each DOE mailbox

Jonathan Cameron
2022-04-29T15:55:14Z

On Thu, 14 Apr 2022 13:32:31 -0700
ira.weiny@intel.com wrote:

> From: Ira Weiny <ira.weiny@intel.com>
>
> CXL kernel drivers optionally need to access DOE mailbox capabilities.
> Access to mailboxes for things such as CDAT, SPDM, and IDE are needed by
> the kernel while other access is designed towards user space usage. An
> example of this is for CXL Compliance Testing (see CXL 2.0 14.16.4
> Compliance Mode DOE) which offers a mechanism to set different test
> modes for a device.
>
> There is no anticipated need for the kernel to share an individual
> mailbox with user space. Thus developing an interface to marshal access
> between the kernel and user space for a single mailbox is unnecessary
> overhead. However, having the kernel relinquish some mailboxes to be
> controlled by user space is a reasonable compromise to share access to
> the device.
>
> The auxiliary bus provides an elegant solution for this. Each DOE
> capability is given its own auxiliary device. This device is controlled
> by a kernel driver by default which restricts access to the mailbox.
> Unbinding the driver from a single auxiliary device (DOE mailbox
> capability) frees the mailbox for user space access. This architecture
> also allows a clear picture on which mailboxes are kernel controlled vs
> not.
>
> Iterate each DOE mailbox capability and create auxiliary bus devices.
> Follow on patches will define a driver for the newly created devices.
>
> sysfs shows the devices.
>
> $ ls -l /sys/bus/auxiliary/devices/
> total 0
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.0 -> ../../../devices/pci0000:bf/0000:bf:00.0/0000:c0:00.0/cxl_pci.doe.0
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.1 -> ../../../devices/pci0000:bf/0000:bf:01.0/0000:c1:00.0/cxl_pci.doe.1
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.2 -> ../../../devices/pci0000:35/0000:35:00.0/0000:36:00.0/cxl_pci.doe.2
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.3 -> ../../../devices/pci0000:35/0000:35:01.0/0000:37:00.0/cxl_pci.doe.3
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.4 -> ../../../devices/pci0000:35/0000:35:00.0/0000:36:00.0/cxl_pci.doe.4
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.5 -> ../../../devices/pci0000:bf/0000:bf:00.0/0000:c0:00.0/cxl_pci.doe.5
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.6 -> ../../../devices/pci0000:35/0000:35:01.0/0000:37:00.0/cxl_pci.doe.6
> lrwxrwxrwx 1 root root 0 Mar 24 10:47 cxl_pci.doe.7 -> ../../../devices/pci0000:bf/0000:bf:01.0/0000:c1:00.0/cxl_pci.doe.7
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

oops. I just replied to v7. The point still stands though.
Repeated briefly below.

>
> ---
> Changes from V7:
> Minor code clean ups
> Rebased on cxl-pending
>
> Changes from V6:
> Move all the auxiliary device stuff to the CXL layer
>
> Changes from V5:
> Split the CXL specific stuff off from the PCI DOE create
> auxiliary device code.
> ---
> drivers/cxl/Kconfig | 1 +
> drivers/cxl/cxlpci.h | 21 +++++++
> drivers/cxl/pci.c | 127 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 149 insertions(+)
>
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> index f64e3984689f..ac0f5ca95431 100644
> --- a/drivers/cxl/Kconfig
> +++ b/drivers/cxl/Kconfig
> @@ -16,6 +16,7 @@ if CXL_BUS
> config CXL_PCI
> tristate "PCI manageability"
> default CXL_BUS
> + select AUXILIARY_BUS
> help
> The CXL specification defines a "CXL memory device" sub-class in the
> PCI "memory controller" base class of devices. Device's identified by
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index 329e7ea3f36a..2ad8715173ce 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -2,6 +2,7 @@
> /* Copyright(c) 2020 Intel Corporation. All rights reserved. */
> #ifndef __CXL_PCI_H__
> #define __CXL_PCI_H__
> +#include <linux/auxiliary_bus.h>
> #include <linux/pci.h>
> #include "cxl.h"
>
> @@ -72,4 +73,24 @@ static inline resource_size_t cxl_regmap_to_base(struct pci_dev *pdev,
> }
>
> int devm_cxl_port_enumerate_dports(struct cxl_port *port);
> +
> +/**
> + * struct cxl_doe_dev - CXL DOE auxiliary bus device
> + *
> + * @adev: Auxiliary bus device
> + * @pdev: PCI device this belongs to
> + * @cap_offset: Capability offset
> + * @use_irq: Set if IRQs are to be used with this mailbox
> + *
> + * This represents a single DOE mailbox device. CXL devices should create this
> + * device and register it on the Auxiliary bus for the CXL DOE driver to drive.
> + */
> +struct cxl_doe_dev {
> + struct auxiliary_device adev;
> + struct pci_dev *pdev;
> + int cap_offset;
> + bool use_irq;
> +};
> +#define DOE_DEV_NAME "doe"
> +
> #endif /* __CXL_PCI_H__ */
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index e7ab9a34d718..41a6f3eb0a5c 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -8,6 +8,7 @@
> #include <linux/mutex.h>
> #include <linux/list.h>
> #include <linux/pci.h>
> +#include <linux/pci-doe.h>
> #include <linux/io.h>
> #include "cxlmem.h"
> #include "cxlpci.h"
> @@ -564,6 +565,128 @@ static void cxl_dvsec_ranges(struct cxl_dev_state *cxlds)
> info->ranges = __cxl_dvsec_ranges(cxlds, info);
> }
>
> +static void cxl_pci_free_irq_vectors(void *data)
> +{
> + pci_free_irq_vectors(data);
> +}
> +
> +static DEFINE_IDA(pci_doe_adev_ida);
> +
> +static void cxl_pci_doe_dev_release(struct device *dev)
> +{
> + struct auxiliary_device *adev = container_of(dev,
> + struct auxiliary_device,
> + dev);
> + struct cxl_doe_dev *doe_dev = container_of(adev, struct cxl_doe_dev,
> + adev);
> +
> + ida_free(&pci_doe_adev_ida, adev->id);
> + kfree(doe_dev);
> +}
> +
> +static void cxl_pci_doe_destroy_device(void *ad)
> +{
> + auxiliary_device_delete(ad);
> + auxiliary_device_uninit(ad);
> +}
> +
> +/**
> + * cxl_pci_create_doe_devices - Create auxiliary bus DOE devices for all DOE
> + * mailboxes found
> + *
> + * @pci_dev: The PCI device to scan for DOE mailboxes
> + *
> + * There is no coresponding destroy of these devices. This function associates
> + * the DOE auxiliary devices created with the pci_dev passed in. That
> + * association is device managed (devm_*) such that the DOE auxiliary device
> + * lifetime is always less than or equal to the lifetime of the pci_dev.
> + *
> + * RETURNS: 0 on success -ERRNO on failure.
> + */
> +static int cxl_pci_create_doe_devices(struct pci_dev *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + bool use_irq = true;
> + int irqs = 0;
> + u16 off = 0;
> + int rc;
> +
> + pci_doe_for_each_off(pdev, off)
> + irqs++;
I believe this is insufficient because there may be other irqs in use
on the device. In a similar fashion to that done in pcie/portdrv_core.c
I think we need to instead find the maximum msi/msix vector number
by reading the config space. Then we request one more vector
than that max value to ensure the vector we need has been requested.

Jonathan

> + pci_info(pdev, "Found %d DOE mailbox's\n", irqs);
> +
> + /*
> + * Allocate enough vectors for the DOE's
> + */
> + rc = pci_alloc_irq_vectors(pdev, irqs, irqs, PCI_IRQ_MSI |
> + PCI_IRQ_MSIX);
> + if (rc != irqs) {
> + pci_err(pdev,
> + "Not enough interrupts for all the DOEs; use polling\n");
> + use_irq = false;
> + /* Some got allocated; clean them up */
> + if (rc > 0)
> + cxl_pci_free_irq_vectors(pdev);
> + } else {
> + /*
> + * Enabling bus mastering is require for MSI/MSIx. It could be
> + * done later within the DOE initialization, but as it
> + * potentially has other impacts keep it here when setting up
> + * the IRQ's.
> + */
> + pci_set_master(pdev);
> + rc = devm_add_action_or_reset(dev,
> + cxl_pci_free_irq_vectors,
> + pdev);
> + if (rc)
> + return rc;
> + }
> +
> + pci_doe_for_each_off(pdev, off) {
> + struct auxiliary_device *adev;
> + struct cxl_doe_dev *new_dev;
> + int id;
> +
> + new_dev = kzalloc(sizeof(*new_dev), GFP_KERNEL);
> + if (!new_dev)
> + return -ENOMEM;
> +
> + new_dev->pdev = pdev;
> + new_dev->cap_offset = off;
> + new_dev->use_irq = use_irq;
> +
> + /* Set up struct auxiliary_device */
> + adev = &new_dev->adev;
> + id = ida_alloc(&pci_doe_adev_ida, GFP_KERNEL);
> + if (id < 0) {
> + kfree(new_dev);
> + return -ENOMEM;
> + }
> +
> + adev->id = id;
> + adev->name = DOE_DEV_NAME;
> + adev->dev.release = cxl_pci_doe_dev_release;
> + adev->dev.parent = dev;
> +
> + if (auxiliary_device_init(adev)) {
> + cxl_pci_doe_dev_release(&adev->dev);
> + return -EIO;
> + }
> +
> + if (auxiliary_device_add(adev)) {
> + auxiliary_device_uninit(adev);
> + return -EIO;
> + }
> +
> + rc = devm_add_action_or_reset(dev, cxl_pci_doe_destroy_device,
> + adev);
> + if (rc)
> + return rc;
> + }
> +
> + return 0;
> +}
> +
> static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> {
> struct cxl_register_map map;
> @@ -630,6 +753,10 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (rc)
> return rc;
>
> + rc = cxl_pci_create_doe_devices(pdev);
> + if (rc)
> + return rc;
> +
> cxl_dvsec_ranges(cxlds);
>
> cxlmd = devm_cxl_add_memdev(cxlds);