From: Jason Gunthorpe <jgg@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: David Airlie <airlied@linux.ie>,
Tony Krowiak <akrowiak@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
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Jani Nikula <jani.nikula@linux.intel.com>,
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Vineeth Vijayan <vneethv@linux.ibm.com>,
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"Raj, Ashok" <ashok.raj@intel.com>,
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Leon Romanovsky <leonro@nvidia.com>,
Max Gurtovoy <mgurtovoy@nvidia.com>,
Yishai Hadas <yishaih@nvidia.com>,
Zhenyu Wang <zhenyuw@linux.intel.com>
Subject: Re: [Intel-gfx] [PATCH v3 09/14] vfio/pci: Change vfio_pci_try_bus_reset() to use the dev_set
Date: Tue, 3 Aug 2021 13:41:52 -0300 [thread overview]
Message-ID: <20210803164152.GC1721383@nvidia.com> (raw)
In-Reply-To: <20210803103406.5e1be269.alex.williamson@redhat.com>
On Tue, Aug 03, 2021 at 10:34:06AM -0600, Alex Williamson wrote:
> On Wed, 28 Jul 2021 21:49:18 -0300
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> > Keep track of all the vfio_devices that have been added to the device set
> > and use this list in vfio_pci_try_bus_reset() instead of trying to work
> > backwards from the pci_device.
> >
> > The dev_set->lock directly prevents devices from joining/leaving the set,
> > which further implies the pci_device cannot change drivers or that the
> > vfio_device be freed, eliminating the need for get/put's.
> >
> > Completeness of the device set can be directly measured by checking if
> > every PCI device in the reset group is also in the device set - which
> > proves that VFIO drivers are attached to everything.
> >
> > 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>
> > drivers/vfio/pci/vfio_pci.c | 148 +++++++++++++++---------------------
> > 1 file changed, 62 insertions(+), 86 deletions(-)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index 5d6db93d6c680f..a1ae9a83a38621 100644
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -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);
> >
> > @@ -2145,7 +2148,7 @@ 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)
> > +static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data)
> > {
> > struct vfio_devices *devs = data;
> > struct vfio_device *device;
> > @@ -2165,8 +2168,11 @@ static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data)
> >
> > vdev = container_of(device, struct vfio_pci_device, vdev);
> >
> > - /* Fault if the device is not unused */
> > - if (device->open_count) {
> > + /*
> > + * Locking multiple devices is prone to deadlock, runaway and
> > + * unwind if we hit contention.
> > + */
> > + if (!vfio_pci_zap_and_vma_lock(vdev, true)) {
> > vfio_device_put(device);
> > return -EBUSY;
> > }
> > @@ -2175,112 +2181,82 @@ static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data)
> > return 0;
> > }
> >
> > -static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data)
> > +static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data)
> > {
> > - struct vfio_devices *devs = data;
> > - struct vfio_device *device;
> > - struct vfio_pci_device *vdev;
> > + struct vfio_device_set *dev_set = data;
> > + struct vfio_device *cur;
> >
> > - if (devs->cur_index == devs->max_index)
> > - return -ENOSPC;
> > + lockdep_assert_held(&dev_set->lock);
> >
> > - 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);
> > + list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
> > + if (cur->dev == &pdev->dev)
> > + return 0;
> > + return -EBUSY;
> > +}
> >
> > - /*
> > - * Locking multiple devices is prone to deadlock, runaway and
> > - * unwind if we hit contention.
> > - */
> > - if (!vfio_pci_zap_and_vma_lock(vdev, true)) {
> > - vfio_device_put(device);
> > - return -EBUSY;
> > +/*
> > + * 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.
> > + */
> > +static struct pci_dev *vfio_pci_find_reset_target(struct vfio_pci_device *vdev)
> > +{
> > + struct vfio_device_set *dev_set = vdev->vdev.dev_set;
> > + struct vfio_pci_device *cur;
> > + bool needs_reset = false;
> > +
> > + /* No VFIO device has an open device FD */
> > + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) {
> > + if (cur->vdev.open_count)
> > + return NULL;
> > + needs_reset |= cur->needs_reset;
> > }
> > + if (!needs_reset)
> > + return NULL;
> >
> > - devs->devices[devs->cur_index++] = vdev;
> > - return 0;
> > + /* All PCI devices in the group to be reset need to be in our dev_set */
> > + if (vfio_pci_for_each_slot_or_bus(
> > + vdev->pdev, vfio_pci_is_device_in_set, dev_set,
> > + !pci_probe_reset_slot(vdev->pdev->slot)))
> > + return NULL;
> > + return cur->pdev;
>
>
> I don't understand the "reset target" aspect of this, cur->pdev is
> simply the last entry in the dev_set->devices_list...
Oh, hum, this got messed up someplace along the way, the original code
was just:
/* 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;
So should this, I'll fix it up, thanks
> 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?
Jason
next prev parent reply other threads:[~2021-08-03 16:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 0:49 [Intel-gfx] [PATCH v3 00/14] Provide core infrastructure for managing open/release Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 01/14] vfio/samples: Remove module get/put Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 02/14] vfio/mbochs: Fix missing error unwind of mbochs_used_mbytes Jason Gunthorpe
2021-07-29 7:21 ` Christoph Hellwig
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 03/14] vfio: Introduce a vfio_uninit_group_dev() API call Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 04/14] vfio: Provide better generic support for open/release vfio_device_ops Jason Gunthorpe
2021-07-29 7:26 ` Christoph Hellwig
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 05/14] vfio/samples: Delete useless open/close Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 06/14] vfio/fsl: Move to the device set infrastructure Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 07/14] vfio/platform: Use open_device() instead of open coding a refcnt scheme Jason Gunthorpe
2021-08-05 12:37 ` Eric Auger
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 08/14] vfio/pci: Move to the device set infrastructure Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 09/14] vfio/pci: Change vfio_pci_try_bus_reset() to use the dev_set Jason Gunthorpe
2021-07-29 7:30 ` Christoph Hellwig
2021-08-03 16:34 ` Alex Williamson
2021-08-03 16:41 ` Jason Gunthorpe [this message]
2021-08-03 16:52 ` Alex Williamson
2021-08-05 11:47 ` Jason Gunthorpe
2021-08-05 17:33 ` Alex Williamson
2021-08-05 23:05 ` Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 10/14] vfio/pci: Reorganize VFIO_DEVICE_PCI_HOT_RESET to use the device set Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 11/14] vfio/mbochs: Fix close when multiple device FDs are open Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 12/14] vfio/ap, ccw: Fix open/close " Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 13/14] vfio/gvt: " Jason Gunthorpe
2021-07-29 0:49 ` [Intel-gfx] [PATCH v3 14/14] vfio: Remove struct vfio_device_ops open/release Jason Gunthorpe
2021-07-29 2:13 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for Provide core infrastructure for managing open/release (rev7) Patchwork
2021-07-29 2:37 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2021-07-29 8:16 ` [Intel-gfx] ✓ Fi.CI.IGT: " Patchwork
2021-08-05 14:26 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for Provide core infrastructure for managing open/release (rev8) Patchwork
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