iommu/vt-d: Fix dmar pte read access not set error

If the default DMA domain of a group doesn't fit a device, it
will still sit in the group but use a private identity domain.
When map/unmap/iova_to_phys come through iommu API, the driver
should still serve them, otherwise, other devices in the same
group will be impacted. Since identity domain has been mapped
with the whole available memory space and RMRRs, we don't need
to worry about the impact on it.

Link: https://www.spinics.net/lists/iommu/msg40416.html
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
Fixes: 942067f ("iommu/vt-d: Identify default domains replaced with private")
Cc: stable@vger.kernel.org # v5.3+
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Tested-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: LuBaolu

drivers/iommu/intel-iommu.c

@@ -5478,9 +5478,6 @@ static int intel_iommu_map(struct iommu_domain *domain,
 	int prot = 0;
 	int ret;
 
-	if (dmar_domain->flags & DOMAIN_FLAG_LOSE_CHILDREN)
-		return -EINVAL;
-
 	if (iommu_prot & IOMMU_READ)
 		prot |= DMA_PTE_READ;
 	if (iommu_prot & IOMMU_WRITE)
@@ -5523,8 +5520,6 @@ static size_t intel_iommu_unmap(struct iommu_domain *domain,
 	/* Cope with horrid API which requires us to unmap more than the
 	   size argument if it happens to be a large-page mapping. */
 	BUG_ON(!pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &level));
-	if (dmar_domain->flags & DOMAIN_FLAG_LOSE_CHILDREN)
-		return 0;
 
 	if (size < VTD_PAGE_SIZE << level_to_offset_bits(level))
 		size = VTD_PAGE_SIZE << level_to_offset_bits(level);
@@ -5556,9 +5551,6 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
 	int level = 0;
 	u64 phys = 0;
 
-	if (dmar_domain->flags & DOMAIN_FLAG_LOSE_CHILDREN)
-		return 0;
-
 	pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &level);
 	if (pte)
 		phys = dma_pte_addr(pte);