From: Alex Williamson alex.williamson@redhat.com
commit d8018a0e9195ba9f0fb9cf0fd3843807c8b952d5 upstream.
Commit d850c2ee5fe2 ("iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions") created a direct-mapped reserved memory region in order to replace the static identity mapping of the ISA address space, where the latter was then removed in commit df4f3c603aeb ("iommu/vt-d: Remove static identity map code"). According to the history of this code and the Kconfig option surrounding it, this direct mapping exists for the benefit of legacy ISA drivers that are not compatible with the DMA API.
In conjuntion with commit 9b77e5c79840 ("vfio/type1: check dma map request is within a valid iova range") this change introduced a regression where the vfio IOMMU backend enforces reserved memory regions per IOMMU group, preventing userspace from creating IOMMU mappings conflicting with prescribed reserved regions. A necessary prerequisite for the vfio change was the introduction of "relaxable" direct mappings introduced by commit adfd37382090 ("iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions"). These relaxable direct mappings provide the same identity mapping support in the default domain, but also indicate that the reservation is software imposed and may be relaxed under some conditions, such as device assignment.
Convert the ISA bridge direct-mapped reserved region to relaxable to reflect that the restriction is self imposed and need not be enforced by drivers such as vfio.
Fixes: 1c5c59fbad20 ("iommu/vt-d: Differentiate relaxable and non relaxable RMRRs") Cc: stable@vger.kernel.org # v5.3+ Link: https://lore.kernel.org/linux-iommu/20191211082304.2d4fab45@x1.home Reported-by: cprt cprt@protonmail.com Tested-by: cprt cprt@protonmail.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Acked-by: Lu Baolu baolu.lu@linux.intel.com Reviewed-by: Eric Auger eric.auger@redhat.com Tested-by: Jerry Snitselaar jsnitsel@redhat.com Reviewed-by: Jerry Snitselaar jsnitsel@redhat.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/iommu/intel-iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -5698,7 +5698,7 @@ static void intel_iommu_get_resv_regions
if ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA) { reg = iommu_alloc_resv_region(0, 1UL << 24, 0, - IOMMU_RESV_DIRECT); + IOMMU_RESV_DIRECT_RELAXABLE); if (reg) list_add_tail(®->list, head); }