On Tue, Aug 03, 2021 at 10:52:25AM -0600, Alex Williamson wrote:
On Tue, 3 Aug 2021 13:41:52 -0300 Jason Gunthorpe jgg@nvidia.com wrote:
On Tue, Aug 03, 2021 at 10:34:06AM -0600, Alex Williamson wrote:
I think the vfio_pci_find_reset_target() function needs to be re-worked to just tell us true/false that it's ok to reset the provided device, not to anoint an arbitrary target device. Thanks,
Yes, though this logic is confusing, why do we need to check if any device needs a reset at this point? If we are being asked to reset vdev shouldn't vdev needs_reset?
Or is the function more of a 'synchronize pending reset' kind of thing?
Yes, the latter. For instance think about a multi-function PCI device such as a GPU. The functions have dramatically different capabilities, some might have function level reset abilities and others not. We want to be able to trigger a bus reset as the last device of the set is released, no matter the order they're released and no matter the capabilities of the device we're currently processing. Thanks,
I worked on this for awhile, I think this is much clearer about what this algorithm is trying to do:
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 5d6db93d6c680f..e418bcbb68facc 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -223,7 +223,7 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_device *vdev) } }
-static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev); +static bool vfio_pci_dev_set_try_reset(struct vfio_device_set *dev_set); static void vfio_pci_disable(struct vfio_pci_device *vdev); static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data);
@@ -404,6 +404,9 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) struct vfio_pci_ioeventfd *ioeventfd, *ioeventfd_tmp; int i, bar;
+ /* For needs_reset */ + lockdep_assert_held(&vdev->vdev.dev_set->lock); + /* Stop the device from further DMA */ pci_clear_master(pdev);
@@ -487,9 +490,7 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) out: pci_disable_device(pdev);
- vfio_pci_try_bus_reset(vdev); - - if (!disable_idle_d3) + if (!vfio_pci_dev_set_try_reset(vdev->vdev.dev_set) && !disable_idle_d3) vfio_pci_set_power_state(vdev, PCI_D3hot); }
@@ -2145,36 +2146,6 @@ static struct pci_driver vfio_pci_driver = { .err_handler = &vfio_err_handlers, };
-static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data) -{ - struct vfio_devices *devs = data; - struct vfio_device *device; - struct vfio_pci_device *vdev; - - if (devs->cur_index == devs->max_index) - return -ENOSPC; - - device = vfio_device_get_from_dev(&pdev->dev); - if (!device) - return -EINVAL; - - if (pci_dev_driver(pdev) != &vfio_pci_driver) { - vfio_device_put(device); - return -EBUSY; - } - - vdev = container_of(device, struct vfio_pci_device, vdev); - - /* Fault if the device is not unused */ - if (device->open_count) { - vfio_device_put(device); - return -EBUSY; - } - - devs->devices[devs->cur_index++] = vdev; - return 0; -} - static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data) { struct vfio_devices *devs = data; @@ -2208,79 +2179,86 @@ static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data) return 0; }
+static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data) +{ + struct vfio_device_set *dev_set = data; + struct vfio_device *cur; + + lockdep_assert_held(&dev_set->lock); + + list_for_each_entry(cur, &dev_set->device_list, dev_set_list) + if (cur->dev == &pdev->dev) + return 0; + return -EBUSY; +} + +static bool vfio_pci_dev_set_needs_reset(struct vfio_device_set *dev_set) +{ + struct vfio_pci_device *cur; + bool needs_reset = false; + + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { + /* No VFIO device in the set can have an open device FD */ + if (cur->vdev.open_count) + return false; + needs_reset |= cur->needs_reset; + } + return needs_reset; +} + /* - * If a bus or slot reset is available for the provided device and: + * If a bus or slot reset is available for the provided dev_set and: * - All of the devices affected by that bus or slot reset are unused - * (!refcnt) * - At least one of the affected devices is marked dirty via * needs_reset (such as by lack of FLR support) - * Then attempt to perform that bus or slot reset. Callers are required - * to hold vdev->dev_set->lock, protecting the bus/slot reset group from - * concurrent opens. A vfio_device reference is acquired for each device - * to prevent unbinds during the reset operation. - * - * NB: vfio-core considers a group to be viable even if some devices are - * bound to drivers like pci-stub or pcieport. Here we require all devices - * to be bound to vfio_pci since that's the only way we can be sure they - * stay put. + * Then attempt to perform that bus or slot reset. + * Returns true if the dev_set was reset. */ -static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev) +static bool vfio_pci_dev_set_try_reset(struct vfio_device_set *dev_set) { - struct vfio_devices devs = { .cur_index = 0 }; - int i = 0, ret = -EINVAL; - bool slot = false; - struct vfio_pci_device *tmp; + struct vfio_pci_device *cur; + struct pci_dev *pdev; + int ret;
- if (!pci_probe_reset_slot(vdev->pdev->slot)) - slot = true; - else if (pci_probe_reset_bus(vdev->pdev->bus)) - return; + lockdep_assert_held(&dev_set->lock);
- if (vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs, - &i, slot) || !i) - return; + /* + * By definition all PCI devices in the dev_set share the same PCI + * reset, so any pci_dev will have the same outcomes for + * pci_probe_reset_*() and pci_reset_bus(). + */ + pdev = list_first_entry(&dev_set->device_list, struct vfio_pci_device, + vdev.dev_set_list)->pdev;
- devs.max_index = i; - devs.devices = kcalloc(i, sizeof(struct vfio_device *), GFP_KERNEL); - if (!devs.devices) - return; + /* Reset of the dev_set is possible */ + if (pci_probe_reset_slot(pdev->slot) && pci_probe_reset_bus(pdev->bus)) + return false;
- if (vfio_pci_for_each_slot_or_bus(vdev->pdev, - vfio_pci_get_unused_devs, - &devs, slot)) - goto put_devs; + if (!vfio_pci_dev_set_needs_reset(dev_set)) + return false;
- /* Does at least one need a reset? */ - for (i = 0; i < devs.cur_index; i++) { - tmp = devs.devices[i]; - if (tmp->needs_reset) { - ret = pci_reset_bus(vdev->pdev); - break; - } + /* + * vfio-core considers a group to be viable and will create a + * vfio_device even if some devices are bound to drivers like pci-stub + * or pcieport. Here we require all PCI devices to be inside our dev_set + * since that ensures they stay put and that every driver controlling + * the device can co-ordinate with the device reset. + */ + if (vfio_pci_for_each_slot_or_bus(pdev, vfio_pci_is_device_in_set, + dev_set, + !pci_probe_reset_slot(pdev->slot))) + return false; + + ret = pci_reset_bus(pdev); + if (ret) + return false; + + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { + cur->needs_reset = false; + if (!disable_idle_d3) + vfio_pci_set_power_state(cur, PCI_D3hot); } - -put_devs: - for (i = 0; i < devs.cur_index; i++) { - tmp = devs.devices[i]; - - /* - * If reset was successful, affected devices no longer need - * a reset and we should return all the collateral devices - * to low power. If not successful, we either didn't reset - * the bus or timed out waiting for it, so let's not touch - * the power state. - */ - if (!ret) { - tmp->needs_reset = false; - - if (tmp != vdev && !disable_idle_d3) - vfio_pci_set_power_state(tmp, PCI_D3hot); - } - - vfio_device_put(&tmp->vdev); - } - - kfree(devs.devices); + return true; }
static void __exit vfio_pci_cleanup(void)