Re: [PATCH 0/4] iommu/vt-d: Fix-up device-domain relationship by refactoring to use iommu group default domain.

From: Lu Baolu
Date: Tue Mar 05 2019 - 01:10:50 EST

Hi James,

Very glad to see this. Thank you!

On 3/4/19 11:41 PM, James Sewart wrote:

This patchset moves IOMMU_DOMAIN_DMA iommu domain management to iommu.c.
This avoids the use of find_or_alloc_domain whose domain assignment is
inconsistent with the iommu grouping as determined by pci_device_group.

Is this a bug fix or an improvement? What's the real issue will it cause
if we go without this patch set?

Best regards,
Lu Baolu

Patch 3 permits domain type IOMMU_DOMAIN_DMA to be allocated via the
iommu_ops api, allowing the default_domain of an iommu group to be set in
iommu.c. This domain will be attached to every device that is brought up
with an iommu group, and the devices reserved regions will be mapped using
regions returned by get_resv_regions.

In intel_iommu_domain_alloc we donât know the IOMMU this domain will be
associated with so we defer full initialisation until
intel_iommu_attach_device. Currently iommu.c:iommu_group_add_device will
try to map a devices reserved regions before attaching the domain which
would cause issue if the domain is not fully initialised. This is
addressed in patch 1 by moving the mapping to after attaching.

Patch 2 implements function apply_resv_region, used in
iommu_group_create_direct_mappings to mark the reserved regions as non
mappable for the dma_map_ops api.

Patch 4 removes the domain lazy allocation logic. Before this patch the
lazy allocation logic would not be used as any domain allocated using
these paths would be replaced when attaching the group default domain.
Default domain allocation has been tested with and without this patch on


James Sewart (4):
iommu: Move iommu_group_create_direct_mappings to after device_attach
iommu/vt-d: Implement apply_resv_region for reserving IOVA ranges
iommu/vt-d: Allow IOMMU_DOMAIN_DMA and IOMMU_DOMAIN_IDENTITY to be allocated
iommu/vt-d: Remove lazy allocation of domains

drivers/iommu/intel-iommu.c | 329 ++++++++++++------------------------
drivers/iommu/iommu.c | 4 +-
2 files changed, 108 insertions(+), 225 deletions(-)