On Sat, 18 Jan 2020 14:25:11 +0000 "Liu, Yi L" <yi.l.liu@xxxxxxxxx> wrote: > > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > > Sent: Friday, January 17, 2020 5:24 AM > > To: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver > > > > On Thu, 16 Jan 2020 12:33:06 +0000 > > "Liu, Yi L" <yi.l.liu@xxxxxxxxx> wrote: > > > > > > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > > > > Sent: Friday, January 10, 2020 6:49 AM > > > > To: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > > > Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver > > > > > > > > On Tue, 7 Jan 2020 20:01:48 +0800 > > > > Liu Yi L <yi.l.liu@xxxxxxxxx> wrote: > > > > > > > > > This patch adds sample driver named vfio-mdev-pci. It is to wrap > > > > > a PCI device as a mediated device. For a pci device, once bound > > > > > to vfio-mdev-pci driver, user space access of this device will > > > > > go through vfio mdev framework. The usage of the device follows > > > > > mdev management method. e.g. user should create a mdev before > > > > > exposing the device to user-space. > > > > > > > > > > Benefit of this new driver would be acting as a sample driver > > > > > for recent changes from "vfio/mdev: IOMMU aware mediated device" > > > > > patchset. Also it could be a good experiment driver for future > > > > > device specific mdev migration support. This sample driver only > > > > > supports singleton iommu groups, for non-singleton iommu groups, > > > > > this sample driver doesn't work. It will fail when trying to assign > > > > > the non-singleton iommu group to VMs. > > > > > > > > > > To use this driver: > > > > > a) build and load vfio-mdev-pci.ko module > > > > > execute "make menuconfig" and config CONFIG_SAMPLE_VFIO_MDEV_PCI > > > > > then load it with following command: > > > > > > sudo modprobe vfio > > > > > > sudo modprobe vfio-pci > > > > > > sudo insmod samples/vfio-mdev-pci/vfio-mdev-pci.ko > > > > > > > > > > b) unbind original device driver > > > > > e.g. use following command to unbind its original driver > > > > > > echo $dev_bdf > /sys/bus/pci/devices/$dev_bdf/driver/unbind > > > > > > > > > > c) bind vfio-mdev-pci driver to the physical device > > > > > > echo $vend_id $dev_id > /sys/bus/pci/drivers/vfio-mdev-pci/new_id > > > > > > > > > > d) check the supported mdev instances > > > > > > ls /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/ > > > > > vfio-mdev-pci-type_name > > > > > > ls /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/\ > > > > > vfio-mdev-pci-type_name/ > > > > > available_instances create device_api devices name > > > > > > > > > > e) create mdev on this physical device (only 1 instance) > > > > > > echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1003" > \ > > > > > /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/\ > > > > > vfio-mdev-pci-type_name/create > > > > > > > > > > f) passthru the mdev to guest > > > > > add the following line in QEMU boot command > > > > > -device vfio-pci,\ > > > > > sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1003 > > > > > > > > > > g) destroy mdev > > > > > > echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1003/\ > > > > > remove > > > > > > > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx> > > > > > Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > > > > > Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > > > > > Suggested-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > > > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx> > > > > > --- > > > > > samples/Kconfig | 10 + > > > > > samples/Makefile | 1 + > > > > > samples/vfio-mdev-pci/Makefile | 4 + > > > > > samples/vfio-mdev-pci/vfio_mdev_pci.c | 397 > > > > ++++++++++++++++++++++++++++++++++ > > > > > 4 files changed, 412 insertions(+) > > > > > create mode 100644 samples/vfio-mdev-pci/Makefile > > > > > create mode 100644 samples/vfio-mdev-pci/vfio_mdev_pci.c > > > > > > > > > > diff --git a/samples/Kconfig b/samples/Kconfig > > > > > index 9d236c3..50d207c 100644 > > > > > --- a/samples/Kconfig > > > > > +++ b/samples/Kconfig > > > > > @@ -190,5 +190,15 @@ config SAMPLE_INTEL_MEI > > > > > help > > > > > Build a sample program to work with mei device. > > > > > > > > > > +config SAMPLE_VFIO_MDEV_PCI > > > > > + tristate "Sample driver for wrapping PCI device as a mdev" > > > > > + select VFIO_PCI_COMMON > > > > > + select VFIO_PCI > > > > > + depends on VFIO_MDEV && VFIO_MDEV_DEVICE > > > > > + help > > > > > + Sample driver for wrapping a PCI device as a mdev. Once bound to > > > > > + this driver, device passthru should through mdev path. > > > > > + > > > > > + If you don't know what to do here, say N. > > > > > > > > > > endif # SAMPLES > > > > > diff --git a/samples/Makefile b/samples/Makefile > > > > > index 5ce50ef..84faced 100644 > > > > > --- a/samples/Makefile > > > > > +++ b/samples/Makefile > > > > > @@ -21,5 +21,6 @@ obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace/ > > > > > obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += ftrace/ > > > > > obj-$(CONFIG_VIDEO_PCI_SKELETON) += v4l/ > > > > > obj-y += vfio-mdev/ > > > > > +obj-y += vfio-mdev-pci/ > > > > > > > > I think we could just lump this into vfio-mdev rather than making > > > > another directory. > > > > > > sure. will move it. :-) > > > > > > > > > > > > subdir-$(CONFIG_SAMPLE_VFS) += vfs > > > > > obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/ > > > > > diff --git a/samples/vfio-mdev-pci/Makefile b/samples/vfio-mdev-pci/Makefile > > > > > new file mode 100644 > > > > > index 0000000..41b2139 > > > > > --- /dev/null > > > > > +++ b/samples/vfio-mdev-pci/Makefile > > > > > @@ -0,0 +1,4 @@ > > > > > +# SPDX-License-Identifier: GPL-2.0-only > > > > > +vfio-mdev-pci-y := vfio_mdev_pci.o > > > > > + > > > > > +obj-$(CONFIG_SAMPLE_VFIO_MDEV_PCI) += vfio-mdev-pci.o > > > > > diff --git a/samples/vfio-mdev-pci/vfio_mdev_pci.c b/samples/vfio-mdev- > > > > pci/vfio_mdev_pci.c > > > > > new file mode 100644 > > > > > index 0000000..b180356 > > > > > --- /dev/null > > > > > +++ b/samples/vfio-mdev-pci/vfio_mdev_pci.c > > > > > @@ -0,0 +1,397 @@ > > > > > +/* > > > > > + * Copyright © 2020 Intel Corporation. > > > > > + * Author: Liu Yi L <yi.l.liu@xxxxxxxxx> > > > > > + * > > > > > + * This program is free software; you can redistribute it and/or modify > > > > > + * it under the terms of the GNU General Public License version 2 as > > > > > + * published by the Free Software Foundation. > > > > > + * > > > > > + * Derived from original vfio_pci.c: > > > > > + * Copyright (C) 2012 Red Hat, Inc. All rights reserved. > > > > > + * Author: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > > > + * > > > > > + * Derived from original vfio: > > > > > + * Copyright 2010 Cisco Systems, Inc. All rights reserved. > > > > > + * Author: Tom Lyon, pugs@xxxxxxxxx > > > > > + */ > > > > > + > > > > > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > > > > > + > > > > > +#include <linux/device.h> > > > > > +#include <linux/eventfd.h> > > > > > +#include <linux/file.h> > > > > > +#include <linux/interrupt.h> > > > > > +#include <linux/iommu.h> > > > > > +#include <linux/module.h> > > > > > +#include <linux/mutex.h> > > > > > +#include <linux/notifier.h> > > > > > +#include <linux/pci.h> > > > > > +#include <linux/pm_runtime.h> > > > > > +#include <linux/slab.h> > > > > > +#include <linux/types.h> > > > > > +#include <linux/uaccess.h> > > > > > +#include <linux/vfio.h> > > > > > +#include <linux/vgaarb.h> > > > > > +#include <linux/nospec.h> > > > > > +#include <linux/mdev.h> > > > > > +#include <linux/vfio_pci_common.h> > > > > > + > > > > > +#define DRIVER_VERSION "0.1" > > > > > +#define DRIVER_AUTHOR "Liu Yi L <yi.l.liu@xxxxxxxxx>" > > > > > +#define DRIVER_DESC "VFIO Mdev PCI - Sample driver for PCI device as a > > > > mdev" > > > > > + > > > > > +#define VFIO_MDEV_PCI_NAME "vfio-mdev-pci" > > > > > + > > > > > +static char ids[1024] __initdata; > > > > > +module_param_string(ids, ids, sizeof(ids), 0); > > > > > +MODULE_PARM_DESC(ids, "Initial PCI IDs to add to the vfio-mdev-pci driver, > > > > format is \"vendor:device[:subvendor[:subdevice[:class[:class_mask]]]]\" and > > > > multiple comma separated entries can be specified"); > > > > > + > > > > > +static bool nointxmask; > > > > > +module_param_named(nointxmask, nointxmask, bool, S_IRUGO | S_IWUSR); > > > > > +MODULE_PARM_DESC(nointxmask, > > > > > + "Disable support for PCI 2.3 style INTx masking. If this resolves > > > > problems for specific devices, report lspci -vvvxxx to linux-pci@xxxxxxxxxxxxxxx > > so > > > > the device can be fixed automatically via the broken_intx_masking flag."); > > > > > + > > > > > +#ifdef CONFIG_VFIO_PCI_VGA > > > > > +static bool disable_vga; > > > > > +module_param(disable_vga, bool, S_IRUGO); > > > > > +MODULE_PARM_DESC(disable_vga, "Disable VGA resource access through > > vfio- > > > > mdev-pci"); > > > > > +#endif > > > > > + > > > > > +static bool disable_idle_d3; > > > > > +module_param(disable_idle_d3, bool, S_IRUGO | S_IWUSR); > > > > > +MODULE_PARM_DESC(disable_idle_d3, > > > > > + "Disable using the PCI D3 low power state for idle, unused devices"); > > > > > + > > > > > +static struct pci_driver vfio_mdev_pci_driver; > > > > > + > > > > > +static ssize_t > > > > > +name_show(struct kobject *kobj, struct device *dev, char *buf) > > > > > +{ > > > > > + return sprintf(buf, "%s-type1\n", dev_name(dev)); > > > > > +} > > > > > + > > > > > +MDEV_TYPE_ATTR_RO(name); > > > > > + > > > > > +static ssize_t > > > > > +available_instances_show(struct kobject *kobj, struct device *dev, char *buf) > > > > > +{ > > > > > + return sprintf(buf, "%d\n", 1); > > > > > +} > > > > > + > > > > > +MDEV_TYPE_ATTR_RO(available_instances); > > > > > + > > > > > +static ssize_t device_api_show(struct kobject *kobj, struct device *dev, > > > > > + char *buf) > > > > > +{ > > > > > + return sprintf(buf, "%s\n", VFIO_DEVICE_API_PCI_STRING); > > > > > +} > > > > > + > > > > > +MDEV_TYPE_ATTR_RO(device_api); > > > > > + > > > > > +static struct attribute *vfio_mdev_pci_types_attrs[] = { > > > > > + &mdev_type_attr_name.attr, > > > > > + &mdev_type_attr_device_api.attr, > > > > > + &mdev_type_attr_available_instances.attr, > > > > > + NULL, > > > > > +}; > > > > > + > > > > > +static struct attribute_group vfio_mdev_pci_type_group1 = { > > > > > + .name = "type1", > > > > > + .attrs = vfio_mdev_pci_types_attrs, > > > > > +}; > > > > > + > > > > > +struct attribute_group *vfio_mdev_pci_type_groups[] = { > > > > > + &vfio_mdev_pci_type_group1, > > > > > + NULL, > > > > > +}; > > > > > + > > > > > +struct vfio_mdev_pci { > > > > > + struct vfio_pci_device *vdev; > > > > > + struct mdev_device *mdev; > > > > > + unsigned long handle; > > > > > +}; > > > > > + > > > > > +static int vfio_mdev_pci_create(struct kobject *kobj, struct mdev_device > > *mdev) > > > > > +{ > > > > > + struct device *pdev; > > > > > + struct vfio_pci_device *vdev; > > > > > + struct vfio_mdev_pci *pmdev; > > > > > + int ret; > > > > > + > > > > > + pdev = mdev_parent_dev(mdev); > > > > > + vdev = dev_get_drvdata(pdev); > > > > > + pmdev = kzalloc(sizeof(struct vfio_mdev_pci), GFP_KERNEL); > > > > > + if (pmdev == NULL) { > > > > > + ret = -EBUSY; > > > > > + goto out; > > > > > + } > > > > > + > > > > > + pmdev->mdev = mdev; > > > > > + pmdev->vdev = vdev; > > > > > + mdev_set_drvdata(mdev, pmdev); > > > > > + ret = mdev_set_iommu_device(mdev_dev(mdev), pdev); > > > > > + if (ret) { > > > > > + pr_info("%s, failed to config iommu isolation for mdev: %s on > > > > pf: %s\n", > > > > > + __func__, dev_name(mdev_dev(mdev)), dev_name(pdev)); > > > > > + goto out; > > > > > + } > > > > > + > > > > > + pr_info("%s, creation succeeded for mdev: %s\n", __func__, > > > > > + dev_name(mdev_dev(mdev))); > > > > > +out: > > > > > + return ret; > > > > > +} > > > > > + > > > > > +static int vfio_mdev_pci_remove(struct mdev_device *mdev) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + > > > > > + kfree(pmdev); > > > > > + pr_info("%s, succeeded for mdev: %s\n", __func__, > > > > > + dev_name(mdev_dev(mdev))); > > > > > + > > > > > + return 0; > > > > > +} > > > > > + > > > > > +static int vfio_mdev_pci_open(struct mdev_device *mdev) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + struct vfio_pci_device *vdev = pmdev->vdev; > > > > > + int ret = 0; > > > > > + > > > > > + if (!try_module_get(THIS_MODULE)) > > > > > + return -ENODEV; > > > > > + > > > > > + vfio_pci_refresh_config(vdev, nointxmask, disable_idle_d3); > > > > > + > > > > > + mutex_lock(&vdev->reflck->lock); > > > > > + > > > > > + if (!vdev->refcnt) { > > > > > + ret = vfio_pci_enable(vdev); > > > > > + if (ret) > > > > > + goto error; > > > > > + > > > > > + vfio_spapr_pci_eeh_open(vdev->pdev); > > > > > + } > > > > > + vdev->refcnt++; > > > > > +error: > > > > > + mutex_unlock(&vdev->reflck->lock); > > > > > + if (!ret) > > > > > + pr_info("Succeeded to open mdev: %s on pf: %s\n", > > > > > + dev_name(mdev_dev(mdev)), dev_name(&pmdev->vdev->pdev- > > > > >dev)); > > > > > + else { > > > > > + pr_info("Failed to open mdev: %s on pf: %s\n", > > > > > + dev_name(mdev_dev(mdev)), dev_name(&pmdev->vdev->pdev- > > > > >dev)); > > > > > + module_put(THIS_MODULE); > > > > > + } > > > > > + return ret; > > > > > +} > > > > > + > > > > > +static void vfio_mdev_pci_release(struct mdev_device *mdev) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + struct vfio_pci_device *vdev = pmdev->vdev; > > > > > + > > > > > + pr_info("Release mdev: %s on pf: %s\n", > > > > > + dev_name(mdev_dev(mdev)), dev_name(&pmdev->vdev->pdev- > > > > >dev)); > > > > > + > > > > > + mutex_lock(&vdev->reflck->lock); > > > > > + > > > > > + if (!(--vdev->refcnt)) { > > > > > + vfio_spapr_pci_eeh_release(vdev->pdev); > > > > > + vfio_pci_disable(vdev); > > > > > + } > > > > > + > > > > > + mutex_unlock(&vdev->reflck->lock); > > > > > + > > > > > + module_put(THIS_MODULE); > > > > > +} > > > > > > > > open() and release() here are almost identical between vfio_pci and > > > > vfio_mdev_pci, which suggests maybe there should be common functions to > > > > call into like we do for the below. > > > > > > yes, let me have more study and do better abstract in next version. :-) > > > > > > > > +static long vfio_mdev_pci_ioctl(struct mdev_device *mdev, unsigned int cmd, > > > > > + unsigned long arg) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + > > > > > + return vfio_pci_ioctl(pmdev->vdev, cmd, arg); > > > > > +} > > > > > + > > > > > +static int vfio_mdev_pci_mmap(struct mdev_device *mdev, > > > > > + struct vm_area_struct *vma) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + > > > > > + return vfio_pci_mmap(pmdev->vdev, vma); > > > > > +} > > > > > + > > > > > +static ssize_t vfio_mdev_pci_read(struct mdev_device *mdev, char __user > > *buf, > > > > > + size_t count, loff_t *ppos) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + > > > > > + return vfio_pci_read(pmdev->vdev, buf, count, ppos); > > > > > +} > > > > > + > > > > > +static ssize_t vfio_mdev_pci_write(struct mdev_device *mdev, > > > > > + const char __user *buf, > > > > > + size_t count, loff_t *ppos) > > > > > +{ > > > > > + struct vfio_mdev_pci *pmdev = mdev_get_drvdata(mdev); > > > > > + > > > > > + return vfio_pci_write(pmdev->vdev, (char __user *)buf, count, ppos); > > > > > +} > > > > > + > > > > > +static const struct mdev_parent_ops vfio_mdev_pci_ops = { > > > > > + .supported_type_groups = vfio_mdev_pci_type_groups, > > > > > + .create = vfio_mdev_pci_create, > > > > > + .remove = vfio_mdev_pci_remove, > > > > > + > > > > > + .open = vfio_mdev_pci_open, > > > > > + .release = vfio_mdev_pci_release, > > > > > + > > > > > + .read = vfio_mdev_pci_read, > > > > > + .write = vfio_mdev_pci_write, > > > > > + .mmap = vfio_mdev_pci_mmap, > > > > > + .ioctl = vfio_mdev_pci_ioctl, > > > > > +}; > > > > > + > > > > > +static int vfio_mdev_pci_driver_probe(struct pci_dev *pdev, > > > > > + const struct pci_device_id *id) > > > > > +{ > > > > > + struct vfio_pci_device *vdev; > > > > > + int ret; > > > > > + > > > > > + if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL) > > > > > + return -EINVAL; > > > > > + > > > > > + /* > > > > > + * Prevent binding to PFs with VFs enabled, this too easily allows > > > > > + * userspace instance with VFs and PFs from the same device, which > > > > > + * cannot work. Disabling SR-IOV here would initiate removing the > > > > > + * VFs, which would unbind the driver, which is prone to blocking > > > > > + * if that VF is also in use by vfio-pci or vfio-mdev-pci. Just > > > > > + * reject these PFs and let the user sort it out. > > > > > + */ > > > > > + if (pci_num_vf(pdev)) { > > > > > + pci_warn(pdev, "Cannot bind to PF with SR-IOV enabled\n"); > > > > > + return -EBUSY; > > > > > + } > > > > > + > > > > > + vdev = kzalloc(sizeof(*vdev), GFP_KERNEL); > > > > > + if (!vdev) > > > > > + return -ENOMEM; > > > > > + > > > > > + vdev->pdev = pdev; > > > > > + vdev->irq_type = VFIO_PCI_NUM_IRQS; > > > > > + mutex_init(&vdev->igate); > > > > > + spin_lock_init(&vdev->irqlock); > > > > > + mutex_init(&vdev->ioeventfds_lock); > > > > > + INIT_LIST_HEAD(&vdev->ioeventfds_list); > > > > > + vdev->nointxmask = nointxmask; > > > > > +#ifdef CONFIG_VFIO_PCI_VGA > > > > > + vdev->disable_vga = disable_vga; > > > > > +#endif > > > > > + vdev->disable_idle_d3 = disable_idle_d3; > > > > > + > > > > > + pci_set_drvdata(pdev, vdev); > > > > > + > > > > > + ret = vfio_pci_reflck_attach(vdev); > > > > > + if (ret) { > > > > > + pci_set_drvdata(pdev, NULL); > > > > > + kfree(vdev); > > > > > + return ret; > > > > > + } > > > > > + > > > > > + if (vfio_pci_is_vga(pdev)) { > > > > > + vga_client_register(pdev, vdev, NULL, vfio_pci_set_vga_decode); > > > > > + vga_set_legacy_decoding(pdev, > > > > > + vfio_pci_set_vga_decode(vdev, false)); > > > > > + } > > > > > + > > > > > + vfio_pci_probe_power_state(vdev); > > > > > + > > > > > + if (!vdev->disable_idle_d3) { > > > > > + /* > > > > > + * pci-core sets the device power state to an unknown value at > > > > > + * bootup and after being removed from a driver. The only > > > > > + * transition it allows from this unknown state is to D0, which > > > > > + * typically happens when a driver calls pci_enable_device(). > > > > > + * We're not ready to enable the device yet, but we do want to > > > > > + * be able to get to D3. Therefore first do a D0 transition > > > > > + * before going to D3. > > > > > + */ > > > > > + vfio_pci_set_power_state(vdev, PCI_D0); > > > > > + vfio_pci_set_power_state(vdev, PCI_D3hot); > > > > > + } > > > > > > > > Ditto here and remove below, this seems like boilerplate that shouldn't > > > > be duplicated per leaf module. Thanks, > > > > > > Sure, the code snippet above may also be abstracted to be a common API > > > provided by vfio-pci-common.ko. :-) > > > > > > I have a confusion which may need confirm with you. Do you also want the > > > below code snippet be placed in the vfio-pci-common.ko and exposed out > > > as a wrapped API? Thus it can be used by sample driver and other future > > > drivers which want to wrap PCI device as a mdev. May be I misundstood > > > your comment. :-( > > > > > > I think some sort of vfio_pci_common_{probe,remove}() would be a > > reasonable starting point where the respective module _{probe,remove} > > functions would call into these and add their module specific code > > around it. That would at least give us a point to cleanup things that > > are only used by the common code in the common code. > > sure, I can start from here if we are still going with this direction. :-) > > > I'm still struggling how we make this user consumable should we accept > > this and progress beyond a proof of concept sample driver though. For > > example, if a vendor actually implements an mdev wrapper driver or even > > just a device specific vfio-pci wrapper, to enable for example > > migration support, how does a user know which driver to use for each > > particular feature? The best I can come up with so far is something > > like was done for vfio-platform reset modules. For instance a module > > that extends features for a given device in vfio-pci might register an > > ops structure and id table with vfio-pci, along with creating a module > > alias (or aliases) for the devices it supports. When a device is > > probed by vfio-pci it could try to match against registered id tables > > to find a device specific ops structure, if one is not found it could > > do a request_module using the PCI vendor and device IDs and some unique > > vfio-pci string, check again, and use the default ops if device > > specific ops are still not present. That would solve the problem on > > the vfio-pci side. > > yeah, this is letting vfio-pci to invoke the ops from vendor drivers/modules. > I think this is what Yan is trying to do. I think I'm suggesting a callback ops structure a level above what Yan previously proposed. For example, could we have device specific vfio_device_ops where the vendor module can call out to common code rather than requiring common code to test for and optionally call out to device specific code. > > For mdevs, I tend to assume that this vfio-mdev-pci > > meta driver is an anomaly only for the purpose of creating a generic > > test device for IOMMU backed mdevs and that "real" mdev vendor > > drivers will just be mdev enlightened host drivers, like i915 and > > nvidia are now. Thanks, > > yes, this vfio-mdev-pci meta driver is just creating a test device. > Do we still go with the current direction, or find any other way > which may be easier for adding this meta driver? I think if the code split allows us to create an environment where vendor drivers can re-use much of vfio-pci while creating a vfio_device_ops that supports additional features for their device and we bring that all together with a request module interface and module aliases to make that work seamlessly, then it has value. A concern I have in only doing this split in order to create the vfio-mdev-pci module is that it leaves open the question and groundwork for forking vfio-pci into multiple vendor specific modules that would become a mess for user's to mange. > Compared with the "real" mdev vendor drivers, it is like a > "vfio-pci + dummy mdev ops" driver. dummy mdev ops means > no vendor specific handling and passthru to vfio-pci codes directly. > > I think this meta driver is even lighter than the "real" mdev vendor > drivers. right? Is it possible to let this driver follow the way of > registering ops structure and id table with vfio-pci? The obstacle > I can see is the meta driver is a generic driver, which means it has > no id table... For the "real" mdev vendor drivers, they naturally have > such info. If vfio-mdev-pci can also get the id info without binding > to a device, it may be possible. thoughts? :-) IDs could be provided via a module option or potentially with build-time options. That might allow us to test all aspects of the above proposal, ie. allowing sub-modules to provide vfio_device_ops for specific devices, allowing those vendor vfio_device_ops to re-use much of the existing vfio-pci code in that implementation, and a mechanism for generically testing IOMMU backed mdevs. That's starting to sound a lot more worthwhile than moving a bunch of code around only to implement a sample driver for the latter. Thoughts? Thanks, Alex
