Re: [PATCH v3 4/8] vfio/pci: Add support for setting driver data inside core layer

Jason Gunthorpe
2022-05-04T00:21:06Z

On Tue, May 03, 2022 at 11:11:24AM -0600, Alex Williamson wrote:
> > @@ -1843,6 +1845,17 @@ int vfio_pci_core_register_device(struct vfio_pci_core_device *vdev)
> > return -EBUSY;
> > }
> >
> > + /*
> > + * The 'struct vfio_pci_core_device' should be the first member of the
> > + * of the structure referenced by 'driver_data' so that it can be
> > + * retrieved with dev_get_drvdata() inside vfio-pci core layer.
> > + */
> > + if ((struct vfio_pci_core_device *)driver_data != vdev) {
> > + pci_warn(pdev, "Invalid driver data\n");
> > + return -EINVAL;
> > + }
>
> It seems a bit odd to me to add a driver_data arg to the function,
> which is actually required to point to the same thing as the existing
> function arg. Is this just to codify the requirement? Maybe others
> can suggest alternatives.
>
> We also need to collaborate with Jason's patch:
>
> https://lore.kernel.org/all/0-v2-0f36bcf6ec1e+64d-vfio_get_from_dev_jgg@nvidia.com/
>
> (and maybe others)
>
> If we implement a change like proposed here that vfio-pci-core sets
> drvdata then we don't need for each variant driver to implement their
> own wrapper around err_handler or err_detected as Jason proposes in the
> linked patch. Thanks,

Oh, I forgot about this series completely.

Yes, we need to pick a method, either drvdata always points at the
core struct, or we wrapper the core functions.

I have an independent version of the above patch that uses the
drvdata, but I chucked it because it was unnecessary for just a couple
of AER functions.

We should probably go back to it though if we are adding more
functions, as the wrapping is a bit repetitive. I'll go and respin
that series then. Abhishek can base on top of it.

My approach was more type-sane though:

commit 12ba94a72d7aa134af8752d6ff78193acdac93ae
Author: Jason Gunthorpe <jgg@ziepe.ca>
Date: Tue Mar 29 16:32:32 2022 -0300

vfio/pci: Have all VFIO PCI drivers store the vfio_pci_core_device in drvdata

Having a consistent pointer in the drvdata will allow the next patch to
make use of the drvdata from some of the core code helpers.

Use a WARN_ON inside vfio_pci_core_unregister_device() to detect drivers
that miss this.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
index 767b5d47631a49..665691967a030c 100644
--- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
+++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
@@ -337,6 +337,14 @@ static int vf_qm_cache_wb(struct hisi_qm *qm)
return 0;
}

+static struct hisi_acc_vf_core_device *hssi_acc_drvdata(struct pci_dev *pdev)
+{
+ struct vfio_pci_core_device *core_device = dev_get_drvdata(&pdev->dev);
+
+ return container_of(core_device, struct hisi_acc_vf_core_device,
+ core_device);
+}
+
static void vf_qm_fun_reset(struct hisi_acc_vf_core_device *hisi_acc_vdev,
struct hisi_qm *qm)
{
@@ -962,7 +970,7 @@ hisi_acc_vfio_pci_get_device_state(struct vfio_device *vdev,

static void hisi_acc_vf_pci_aer_reset_done(struct pci_dev *pdev)
{
- struct hisi_acc_vf_core_device *hisi_acc_vdev = dev_get_drvdata(&pdev->dev);
+ struct hisi_acc_vf_core_device *hisi_acc_vdev = hssi_acc_drvdata(pdev);

if (hisi_acc_vdev->core_device.vdev.migration_flags !=
VFIO_MIGRATION_STOP_COPY)
@@ -1278,7 +1286,7 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device
if (ret)
goto out_free;

- dev_set_drvdata(&pdev->dev, hisi_acc_vdev);
+ dev_set_drvdata(&pdev->dev, &hisi_acc_vdev->core_device);
return 0;

out_free:
@@ -1289,7 +1297,7 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device

static void hisi_acc_vfio_pci_remove(struct pci_dev *pdev)
{
- struct hisi_acc_vf_core_device *hisi_acc_vdev = dev_get_drvdata(&pdev->dev);
+ struct hisi_acc_vf_core_device *hisi_acc_vdev = hssi_acc_drvdata(pdev);

vfio_pci_core_unregister_device(&hisi_acc_vdev->core_device);
vfio_pci_core_uninit_device(&hisi_acc_vdev->core_device);
diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
index bbec5d288fee97..3391f965abd9f0 100644
--- a/drivers/vfio/pci/mlx5/main.c
+++ b/drivers/vfio/pci/mlx5/main.c
@@ -39,6 +39,14 @@ struct mlx5vf_pci_core_device {
struct mlx5_vf_migration_file *saving_migf;
};

+static struct mlx5vf_pci_core_device *mlx5vf_drvdata(struct pci_dev *pdev)
+{
+ struct vfio_pci_core_device *core_device = dev_get_drvdata(&pdev->dev);
+
+ return container_of(core_device, struct mlx5vf_pci_core_device,
+ core_device);
+}
+
static struct page *
mlx5vf_get_migration_page(struct mlx5_vf_migration_file *migf,
unsigned long offset)
@@ -505,7 +513,7 @@ static int mlx5vf_pci_get_device_state(struct vfio_device *vdev,

static void mlx5vf_pci_aer_reset_done(struct pci_dev *pdev)
{
- struct mlx5vf_pci_core_device *mvdev = dev_get_drvdata(&pdev->dev);
+ struct mlx5vf_pci_core_device *mvdev = mlx5vf_drvdata(pdev);

if (!mvdev->migrate_cap)
return;
@@ -618,7 +626,7 @@ static int mlx5vf_pci_probe(struct pci_dev *pdev,
if (ret)
goto out_free;

- dev_set_drvdata(&pdev->dev, mvdev);
+ dev_set_drvdata(&pdev->dev, &mvdev->core_device);
return 0;

out_free:
@@ -629,7 +637,7 @@ static int mlx5vf_pci_probe(struct pci_dev *pdev,

static void mlx5vf_pci_remove(struct pci_dev *pdev)
{
- struct mlx5vf_pci_core_device *mvdev = dev_get_drvdata(&pdev->dev);
+ struct mlx5vf_pci_core_device *mvdev = mlx5vf_drvdata(pdev);

vfio_pci_core_unregister_device(&mvdev->core_device);
vfio_pci_core_uninit_device(&mvdev->core_device);
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 06b6f3594a1316..53ad39d617653d 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -262,6 +262,10 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev)
u16 cmd;
u8 msix_pos;

+ /* Drivers must set the vfio_pci_core_device to their drvdata */
+ if (WARN_ON(vdev != dev_get_drvdata(&vdev->pdev->dev)))
+ return -EINVAL;
+
vfio_pci_set_power_state(vdev, PCI_D0);

/* Don't allow our initial saved state to include busmaster */