Hi Alex,
On 12/11/19 9:28 PM, Alex Williamson wrote:
> 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: d850c2ee5fe2 ("iommu/vt-d: Expose ISA direct mapping region via
> iommu_get_resv_regions")
Maybe it is rather a fix of my patch, below, since above patch landed
upstream before the IOMMU_RESV_DIRECT_RELAXABLE availability.
Fixes: 1c5c59fbad20 ("iommu/vt-d: Differentiate relaxable and non
relaxable RMRRs")
> Cc: sta...@vger.kernel.org # v5.3+
> Link: https://lore.kernel.org/linux-iommu/20191211082304.2d4fa...@x1.home
> Reported-by: cprt <c...@protonmail.com>
> Tested-by: cprt <c...@protonmail.com>
> Signed-off-by: Alex Williamson <alex.william...@redhat.com>
Besides
Reviewed-by: Eric Auger <eric.au...@redhat.com>
Thanks
Eric
> ---
> drivers/iommu/intel-iommu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 0c8d81f56a30..6eb0dd7489a1 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5737,7 +5737,7 @@ static void intel_iommu_get_resv_regions(struct device
> *device,
>
> 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);
> }
>
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