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vfio/pci: Change vfio_pci_try_bus_reset() to use the dev_set

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vfio_pci_try_bus_reset() is triggering a reset of the entire_dev set if
any device within it has accumulated a needs_reset. This reset can only be
done once all of the drivers operating the PCI devices to be reset are in
a known safe state.

Make this clearer by directly operating on the dev_set instead of the
vfio_pci_device. Rename the function to vfio_pci_dev_set_try_reset().

Use the device list inside the dev_set to check that all drivers are in a
safe state instead of working backwards from the pci_device.

The dev_set->lock directly prevents devices from joining/leaving the set,
or changing their state, which further implies the pci_device cannot
change drivers or that the vfio_device be freed, eliminating the need for
get/put's.

If a pci_device to be reset is not in the dev_set then the reset cannot be
used as we can't know what the state of that driver is. Directly measure
this by checking that every pci_device is in the dev_set - which
effectively proves that VFIO drivers are attached to everything.

Remove the odd interaction around vfio_pci_set_power_state() - have the
only caller avoid its redundant vfio_pci_set_power_state() instead of
avoiding it inside vfio_pci_dev_set_try_reset().

This restructuring corrects a call to pci_dev_driver() without holding the
device_lock() and removes a hard wiring to &vfio_pci_driver.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/9-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Jason Gunthorpe 2021-08-05 22:19:05 -03:00 committed by Alex Williamson
parent 2cd8b14aaa
commit a882c16a2b
1 changed files with 86 additions and 96 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

182
drivers/vfio/pci/vfio_pci.c
View file

@ -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 +2179,98 @@ static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data)
return 0;
}
/*
* If a bus or slot reset is available for the provided device 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.
*/
static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data)
{
struct vfio_devices devs = { .cur_index = 0 };
int i = 0, ret = -EINVAL;
bool slot = false;
struct vfio_pci_device *tmp;
struct vfio_device_set *dev_set = data;
struct vfio_device *cur;
if (!pci_probe_reset_slot(vdev->pdev->slot))
slot = true;
else if (pci_probe_reset_bus(vdev->pdev->bus))
return;
list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
if (cur->dev == &pdev->dev)
return 0;
return -EBUSY;
}
if (vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs,
&i, slot) || !i)
return;
/*
* 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.
*
* Returns the pci_dev to pass to pci_reset_bus() if every PCI device to be
* reset is inside the dev_set, and pci_reset_bus() can succeed. NULL otherwise.
*/
static struct pci_dev *
vfio_pci_dev_set_resettable(struct vfio_device_set *dev_set)
{
struct pci_dev *pdev;
devs.max_index = i;
devs.devices = kcalloc(i, sizeof(struct vfio_device *), GFP_KERNEL);
if (!devs.devices)
return;
if (vfio_pci_for_each_slot_or_bus(vdev->pdev,
vfio_pci_get_unused_devs,
&devs, slot))
goto put_devs;
/* 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;
}
}
put_devs:
for (i = 0; i < devs.cur_index; i++) {
tmp = devs.devices[i];
lockdep_assert_held(&dev_set->lock);
/*
* 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.
* 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().
*/
if (!ret) {
tmp->needs_reset = false;
pdev = list_first_entry(&dev_set->device_list, struct vfio_pci_device,
vdev.dev_set_list)->pdev;
if (tmp != vdev && !disable_idle_d3)
vfio_pci_set_power_state(tmp, PCI_D3hot);
/* pci_reset_bus() is supported */
if (pci_probe_reset_slot(pdev->slot) && pci_probe_reset_bus(pdev->bus))
return NULL;
if (vfio_pci_for_each_slot_or_bus(pdev, vfio_pci_is_device_in_set,
dev_set,
!pci_probe_reset_slot(pdev->slot)))
return NULL;
return pdev;
}
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;
}
vfio_device_put(&tmp->vdev);
/*
* 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
* - 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.
* Returns true if the dev_set was reset.
*/
static bool vfio_pci_dev_set_try_reset(struct vfio_device_set *dev_set)
{
struct vfio_pci_device *cur;
struct pci_dev *pdev;
int ret;
if (!vfio_pci_dev_set_needs_reset(dev_set))
return false;
pdev = vfio_pci_dev_set_resettable(dev_set);
if (!pdev)
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);
}
kfree(devs.devices);
return true;
}
static void __exit vfio_pci_cleanup(void)