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Message-ID: <e9754210-0907-56ac-c286-0aa82ee79e4c@linux.ibm.com>
Date: Fri, 7 Oct 2022 09:28:47 -0400
From: Matthew Rosato <mjrosato@...ux.ibm.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>,
Pierre Morel <pmorel@...ux.ibm.com>, iommu@...ts.linux.dev
Cc: linux-s390@...r.kernel.org, borntraeger@...ux.ibm.com,
hca@...ux.ibm.com, gor@...ux.ibm.com,
gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
svens@...ux.ibm.com, joro@...tes.org, will@...nel.org,
robin.murphy@....com, jgg@...dia.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/6] iommu/s390: Fix duplicate domain attachments
On 10/7/22 5:50 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@...ux.ibm.com>
Looks good to me now, thanks!
Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
> v5->v6:
> - Only set zdev->dma_table once zpci_register_ioat() succeeded (Matt)
> v4->v5:
> - Unregister IOAT and set zdev->dma_table on error (Matt)
>
> drivers/iommu/s390-iommu.c | 106 ++++++++++++++++---------------------
> 1 file changed, 45 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index c898bcbbce11..96173cfee324 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -79,10 +79,36 @@ static void s390_domain_free(struct iommu_domain *domain)
> {
> struct s390_domain *s390_domain = to_s390_domain(domain);
>
> + WARN_ON(!list_empty(&s390_domain->devices));
> dma_cleanup_tables(s390_domain->dma_table);
> kfree(s390_domain);
> }
>
> +static void __s390_iommu_detach_device(struct zpci_dev *zdev)
> +{
> + struct s390_domain *s390_domain = zdev->s390_domain;
> + struct s390_domain_device *domain_device, *tmp;
> + unsigned long flags;
> +
> + if (!s390_domain)
> + return;
> +
> + spin_lock_irqsave(&s390_domain->list_lock, flags);
> + list_for_each_entry_safe(domain_device, tmp, &s390_domain->devices,
> + list) {
> + if (domain_device->zdev == zdev) {
> + list_del(&domain_device->list);
> + kfree(domain_device);
> + break;
> + }
> + }
> + spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> +
> + zpci_unregister_ioat(zdev, 0);
> + zdev->s390_domain = NULL;
> + zdev->dma_table = NULL;
> +}
> +
> 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;
> @@ -99,24 +125,18 @@ 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));
> + virt_to_phys(s390_domain->dma_table));
> if (cc) {
> rc = -EIO;
> - goto out_restore;
> + goto out_free;
> }
> + zdev->dma_table = s390_domain->dma_table;
>
> spin_lock_irqsave(&s390_domain->list_lock, flags);
> /* First device defines the DMA range limits */
> @@ -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);
>
> @@ -155,32 +170,12 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
> static void s390_iommu_detach_device(struct iommu_domain *domain,
> struct device *dev)
> {
> - struct s390_domain *s390_domain = to_s390_domain(domain);
> struct zpci_dev *zdev = to_zpci_dev(dev);
> - struct s390_domain_device *domain_device, *tmp;
> - unsigned long flags;
> - int found = 0;
>
> - if (!zdev)
> - return;
> + WARN_ON(zdev->s390_domain != to_s390_domain(domain));
>
> - spin_lock_irqsave(&s390_domain->list_lock, flags);
> - list_for_each_entry_safe(domain_device, tmp, &s390_domain->devices,
> - list) {
> - if (domain_device->zdev == zdev) {
> - list_del(&domain_device->list);
> - kfree(domain_device);
> - found = 1;
> - break;
> - }
> - }
> - spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> -
> - if (found && (zdev->s390_domain == s390_domain)) {
> - zdev->s390_domain = NULL;
> - zpci_unregister_ioat(zdev, 0);
> - zpci_dma_init_device(zdev);
> - }
> + __s390_iommu_detach_device(zdev);
> + zpci_dma_init_device(zdev);
> }
>
> static struct iommu_device *s390_iommu_probe_device(struct device *dev)
> @@ -193,24 +188,13 @@ static struct iommu_device *s390_iommu_probe_device(struct device *dev)
> static void s390_iommu_release_device(struct device *dev)
> {
> struct zpci_dev *zdev = to_zpci_dev(dev);
> - struct iommu_domain *domain;
>
> /*
> - * This is a workaround for a scenario where the IOMMU API common code
> - * "forgets" to call the detach_dev callback: After binding a device
> - * to vfio-pci and completing the VFIO_SET_IOMMU ioctl (which triggers
> - * the attach_dev), removing the device via
> - * "echo 1 > /sys/bus/pci/devices/.../remove" won't trigger detach_dev,
> - * only release_device will be called via the BUS_NOTIFY_REMOVED_DEVICE
> - * notifier.
> - *
> - * So let's call detach_dev from here if it hasn't been called before.
> + * release_device is expected to detach any domain currently attached
> + * to the device, but keep it attached to other devices in the group.
> */
> - if (zdev && zdev->s390_domain) {
> - domain = iommu_get_domain_for_dev(dev);
> - if (domain)
> - s390_iommu_detach_device(domain, dev);
> - }
> + if (zdev)
> + __s390_iommu_detach_device(zdev);
> }
>
> static int s390_iommu_update_trans(struct s390_domain *s390_domain,
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