VFIO currently exposes the usable IOVA regions through the VFIO_IOMMU_GET_INFO ioctl. However it fails to take into account the dma_mask of the devices within the container. The top limit currently is defined by the iommu aperture.
So, for instance, if the IOMMU supports up to 48bits, it may give the impression the max IOVA is 48b while a device may have a dma_mask of 42b. So this API cannot really be used to compute the max usable IOVA. This patch removes the IOVA region beyond the dma_mask's. As we start to expose this reserved region in the sysfs file /sys/kernel/iommu_groups/<n>/reserved_regions, we also need to expose the IOVA range beyond the IOMMU aperture to handle the case where the dma_mask would have a higher number of bits than the iommu max input address. Those out-of-reach regions get the IOMMU_RESV_RESERVED type. This is a change to the ABI as this reserved region was not yet exposed in sysfs /sys/kernel/iommu_groups/<n>/reserved_regions or through the VFIO ioctl. Document that change. Signed-off-by: Eric Auger <eric.au...@redhat.com> --- .../ABI/testing/sysfs-kernel-iommu_groups | 7 ++++ drivers/iommu/iommu.c | 39 +++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups index 017f5bc3920c..2f316686c88b 100644 --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -33,3 +33,10 @@ Description: In case an RMRR is used only by graphics or USB devices it is now exposed as "direct-relaxable" instead of "direct". In device assignment use case, for instance, those RMRR are considered to be relaxable and safe. + +What: /sys/kernel/iommu_groups/reserved_regions +Date: Sept 2020 +KernelVersion: v5.11 +Contact: Eric Auger <eric.au...@redhat.com> +Description: Regions beyond the device dma_mask and the iommu aperture + now are exposed as IOMMU_RESV_RESERVED reserved regions. diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index dd8cda340e62..d797f07b3625 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2511,9 +2511,48 @@ EXPORT_SYMBOL_GPL(iommu_domain_set_attr); void iommu_get_resv_regions(struct device *dev, struct list_head *list) { const struct iommu_ops *ops = dev->bus->iommu_ops; + struct iommu_resv_region *region; + struct iommu_domain *domain; + + domain = iommu_get_domain_for_dev(dev); + + if (domain) { + struct iommu_domain_geometry geo; + + if (iommu_domain_get_attr(domain, DOMAIN_ATTR_GEOMETRY, &geo)) + return; + + if (geo.aperture_end < ULLONG_MAX && geo.aperture_end != geo.aperture_start) { + region = iommu_alloc_resv_region(geo.aperture_end + 1, + ULLONG_MAX - geo.aperture_end, + 0, IOMMU_RESV_RESERVED); + if (!region) + return; + list_add_tail(®ion->list, list); + } + + if (geo.aperture_start > 0) { + region = iommu_alloc_resv_region(0, geo.aperture_start, + 0, IOMMU_RESV_RESERVED); + if (!region) + return; + list_add_tail(®ion->list, list); + } + } if (ops && ops->get_resv_regions) ops->get_resv_regions(dev, list); + + if (!dev->dma_mask || *dev->dma_mask == ULLONG_MAX) + return; + + region = iommu_alloc_resv_region(*dev->dma_mask + 1, + ULLONG_MAX - *dev->dma_mask, + 0, IOMMU_RESV_RESERVED); + if (!region) + return; + + list_add_tail(®ion->list, list); } void iommu_put_resv_regions(struct device *dev, struct list_head *list) -- 2.21.3