On 10/6/22 10:46 AM, Niklas Schnelle wrote:
> Since commit fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev
> calls") we can end up with duplicates in the list of devices attached to
> a domain. This is inefficient and confusing since only one domain can
> actually be in control of the IOMMU translations for a device. Fix this
> by detaching the device from the previous domain, if any, on attach.
> Add a WARN_ON() in case we still have attached devices on freeing the
> domain. While here remove the re-attach on failure dance as it was
> determined to be unlikely to help and may confuse debug and recovery.
>
> Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls")
> Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> ---
> v4->v5:
> - Unregister IOAT and set zdev->dma_table on error (Matt)
>
...
> static int s390_iommu_attach_device(struct iommu_domain *domain,
> struct device *dev)
> {
> @@ -90,7 +116,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
> struct zpci_dev *zdev = to_zpci_dev(dev);
> struct s390_domain_device *domain_device;
> unsigned long flags;
> - int cc, rc;
> + int cc, rc = 0;
>
> if (!zdev)
> return -ENODEV;
> @@ -99,23 +125,17 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
> if (!domain_device)
> return -ENOMEM;
>
> - if (zdev->dma_table && !zdev->s390_domain) {
> - cc = zpci_dma_exit_device(zdev);
> - if (cc) {
> - rc = -EIO;
> - goto out_free;
> - }
> - }
> -
> if (zdev->s390_domain)
> - zpci_unregister_ioat(zdev, 0);
> + __s390_iommu_detach_device(zdev);
> + else if (zdev->dma_table)
> + zpci_dma_exit_device(zdev);
>
> zdev->dma_table = s390_domain->dma_table;
> cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> virt_to_phys(zdev->dma_table));
> if (cc) {
> rc = -EIO;
> - goto out_restore;
> + goto out_free;
> }
Hmm, with this we will leave attach_dev with a zdev->dma_table associated with this domain (not one generated via zpci_dma_init_device) and zdev->s390_domain == 0. Won't this cause both s390_domain_free and zpci_dma_exit_device() to try and free the same dma table?
I think we also have to leave with a NULL zdev->dma_table in this case too (you technically could skip the zpci_unregister_ioat)
>
> spin_lock_irqsave(&s390_domain->list_lock, flags);
> @@ -127,9 +147,9 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
> /* Allow only devices with identical DMA range limits */
> } else if (domain->geometry.aperture_start != zdev->start_dma ||
> domain->geometry.aperture_end != zdev->end_dma) {
> - rc = -EINVAL;
> spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> - goto out_restore;
> + rc = -EINVAL;
> + goto out_unregister;
> }
> domain_device->zdev = zdev;
> zdev->s390_domain = s390_domain;
> @@ -138,14 +158,9 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
>
> return 0;
>
> -out_restore:
> - if (!zdev->s390_domain) {
> - zpci_dma_init_device(zdev);
> - } else {
> - zdev->dma_table = zdev->s390_domain->dma_table;
> - zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> - virt_to_phys(zdev->dma_table));
> - }
> +out_unregister:
> + zpci_unregister_ioat(zdev, 0);
> + zdev->dma_table = NULL;
> out_free:
> kfree(domain_device);
>
