On Thu, 2022-10-06 at 17:02 -0400, Matthew Rosato wrote:
> On 10/6/22 10:46 AM, Niklas Schnelle wrote:
> > The s390 IOMMU driver currently sets the IOMMU domain's aperture to
> > match the device specific DMA address range of the device that is first
> > attached. This is not ideal. For one if the domain has no device
> > attached in the meantime the aperture could be shrunk allowing
> > translations outside the aperture to exist in the translation tables.
> > Also this is a bit of a misuse of the aperture which really should
> > describe what addresses can be translated and not some device specific
> > limitations.
> >
> > Instead of misusing the aperture like this we can instead create
> > reserved ranges for the ranges inaccessible to the attached devices
> > allowing devices with overlapping ranges to still share an IOMMU domain.
> > This also significantly simplifies s390_iommu_attach_device() allowing
> > us to move the aperture check to the beginning of the function and
> > removing the need to hold the device list's lock to check the aperture.
> >
> > As we then use the same aperture for all domains and it only depends on
> > the table properties we can already check zdev->start_dma/end_dma at
> > probe time and turn the check on attach into a WARN_ON().
> >
> > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
>
> Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
>
> > ---
> > v4->v5:
> > - Make aperture check in attach a WARN_ON() and fail in probe if
> > zdev->start_dma/end_dma doesn't git in aperture (Jason)
> >
> > drivers/iommu/s390-iommu.c | 65 +++++++++++++++++++++++++-------------
> > 1 file changed, 43 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> > index 9b3ae4b14636..1f6c9bee9a80 100644
> > --- a/drivers/iommu/s390-iommu.c
> > +++ b/drivers/iommu/s390-iommu.c
> > @@ -62,6 +62,9 @@ static struct iommu_domain *s390_domain_alloc(unsigned domain_type)
> > kfree(s390_domain);
> > return NULL;
> > }
> > + s390_domain->domain.geometry.force_aperture = true;
> > + s390_domain->domain.geometry.aperture_start = 0;
> > + s390_domain->domain.geometry.aperture_end = ZPCI_TABLE_SIZE_RT - 1;
> >
> > spin_lock_init(&s390_domain->dma_table_lock);
> > spin_lock_init(&s390_domain->list_lock);
> > @@ -102,46 +105,32 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
> > struct s390_domain *s390_domain = to_s390_domain(domain);
> > struct zpci_dev *zdev = to_zpci_dev(dev);
> > unsigned long flags;
> > - int cc, rc = 0;
> > + int cc;
> >
> > if (!zdev)
> > return -ENODEV;
> >
> > + WARN_ON(domain->geometry.aperture_start > zdev->end_dma ||
> > + domain->geometry.aperture_end < zdev->start_dma);
> > +
I think this one should still return with -EINVAL.
> > if (zdev->s390_domain)
> > __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)
> > return -EIO;
> >
> > - spin_lock_irqsave(&s390_domain->list_lock, flags);
> > - /* First device defines the DMA range limits */
> > - if (list_empty(&s390_domain->devices)) {
> > - domain->geometry.aperture_start = zdev->start_dma;
> > - domain->geometry.aperture_end = zdev->end_dma;
> > - domain->geometry.force_aperture = true;
> > - /* Allow only devices with identical DMA range limits */
> > - } else if (domain->geometry.aperture_start != zdev->start_dma ||
> > - domain->geometry.aperture_end != zdev->end_dma) {
> > - spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> > - rc = -EINVAL;
> > - goto out_unregister;
> > - }
> > + zdev->dma_table = s390_domain->dma_table;
> > zdev->s390_domain = s390_domain;
> > +
> > + spin_lock_irqsave(&s390_domain->list_lock, flags);
> > list_add(&zdev->iommu_list, &s390_domain->devices);
> > spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> >
> > return 0;
> > -
> > -out_unregister:
> > - zpci_unregister_ioat(zdev, 0);
> > - zdev->dma_table = NULL;
> > -
> > - return rc;
> > }
> >
> >
---8<---
