Re: [PATCH 1/1] iommu/vt-d: Restore previous domain::aperture_end calculation

From: Baolu Lu

Date: Thu Nov 20 2025 - 20:44:06 EST

On 11/20/25 21:00, Jason Gunthorpe wrote:
On Thu, Nov 20, 2025 at 03:25:24PM +0800, Lu Baolu wrote:
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2817,6 +2817,16 @@ intel_iommu_domain_alloc_first_stage(struct device *dev,
cfg.common.hw_max_vasz_lg2 = 57;
else
cfg.common.hw_max_vasz_lg2 = 48;
+
+ /*
+ * Spec 3.6 First-Stage Translation:
+ *
+ * Software must limit addresses to less than the minimum of MGAW
+ * and the lower canonical address width implied by FSPM (i.e.,
+ * 47-bit when FSPM is 4-level and 56-bit when FSPM is 5-level).
+ */
+ cfg.common.hw_max_vasz_lg2 = min(cap_mgaw(iommu->cap),
+ cfg.common.hw_max_vasz_lg2);
cfg.common.hw_max_oasz_lg2 = 52;
cfg.common.features = BIT(PT_FEAT_SIGN_EXTEND) |
BIT(PT_FEAT_FLUSH_RANGE);
This is missing the hunk for paging_domain_compatible_first_stage(), I
think that is important!

Yes. I want to make that a separate patch as that will be Cc'd to stable
and backported further than this one. We should have such a
compatibility check even without the generic iopt conversion, right?

Thanks,
baolu