[PATCH v3 13/14] gpu: nova-core: add KUnit tests for the interrupt tree and HALs

[John Hubbard]

Neither the per-architecture interrupt policy nor the vector arithmetic
touches hardware, so KUnit can cover both without a GPU.

Add three suites:

* nova_core_gin_tree covers the vector arithmetic: the leaf index
  bounds, the leaves and subtrees a leaf count implies, the leaf and bit
  a vector maps to, the check that rejects a vector outside the tree,
  the subtree-set operations and iteration, and that every supported
  chipset implements the subtree carrying the GSP notification.

* nova_core_gin_hal covers the tree size on each family, and the rearm
  method for each family and MSI type.

* nova_core_falcon_hal covers two per-chipset falcon gates: whether the
  interrupt retrigger register exists, and where the RISC-V interrupt
  routing registers sit. GA100 falls on a different side of each, and
  shares the Turing HAL, so neither gate can be keyed on the HAL.

Assisted-by: Cursor:claude-opus-5
Reviewed-by: Will Pierce <wpierce@xxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 drivers/gpu/nova-core/falcon/hal.rs         |  43 +++++++
 drivers/gpu/nova-core/irq/hal.rs            |  64 ++++++++++
 drivers/gpu/nova-core/irq/interrupt_tree.rs | 131 ++++++++++++++++++++
 3 files changed, 238 insertions(+)

diff --git a/drivers/gpu/nova-core/falcon/hal.rs b/drivers/gpu/nova-core/falcon/hal.rs
index 5272b3b63ae4..aa89b553ef53 100644
--- a/drivers/gpu/nova-core/falcon/hal.rs
+++ b/drivers/gpu/nova-core/falcon/hal.rs
@@ -146,3 +146,46 @@ pub(super) fn falcon_hal<E: FalconEngine + 'static>(
 
     Ok(hal)
 }
+
+#[kunit_tests(nova_core_falcon_hal)]
+mod tests {
+    use super::*;
+
+    /// Only Turing falcons lack the interrupt retrigger register. GA100 has it even though
+    /// [`falcon_hal`] gives GA100 the Turing HAL, which is why the gate is keyed on the
+    /// architecture instead.
+    #[test]
+    fn intr_retrigger_gate_per_arch() {
+        assert!(!has_intr_retrigger(Chipset::TU102));
+
+        for chipset in [
+            Chipset::GA100,
+            Chipset::GA102,
+            Chipset::AD102,
+            Chipset::GH100,
+            Chipset::GB100,
+            Chipset::GB202,
+        ] {
+            assert!(has_intr_retrigger(chipset));
+        }
+    }
+
+    /// GA102 moved the RISC-V interrupt routing registers. GA100 kept the Turing offsets even
+    /// though it is Ampere, so the two gates in this module do not agree on GA100.
+    #[test]
+    fn riscv_routing_offsets_split_at_ga102() {
+        for chipset in [Chipset::TU102, Chipset::TU116, Chipset::GA100] {
+            assert!(has_turing_riscv_routing(chipset));
+        }
+
+        for chipset in [
+            Chipset::GA102,
+            Chipset::AD102,
+            Chipset::GH100,
+            Chipset::GB100,
+            Chipset::GB202,
+        ] {
+            assert!(!has_turing_riscv_routing(chipset));
+        }
+    }
+}
diff --git a/drivers/gpu/nova-core/irq/hal.rs b/drivers/gpu/nova-core/irq/hal.rs
index 07604458dbbb..e844ade089e5 100644
--- a/drivers/gpu/nova-core/irq/hal.rs
+++ b/drivers/gpu/nova-core/irq/hal.rs
@@ -104,3 +104,67 @@ pub(super) fn cpu_interrupt_hal(chipset: Chipset) -> &'static dyn CpuInterruptHa
         }
     }
 }
+
+#[kunit_tests(nova_core_gin_hal)]
+mod tests {
+    use super::*;
+
+    use crate::gpu::Chipset;
+
+    /// Pre-Hopper parts have an 8-leaf tree.
+    #[test]
+    fn pre_hopper_tree_size() {
+        for chipset in [Chipset::TU102, Chipset::GA102, Chipset::AD102] {
+            assert_eq!(cpu_interrupt_hal(chipset).leaf_count(), LeafCount::Eight);
+        }
+    }
+
+    /// Hopper and later implement a 16-leaf tree.
+    #[test]
+    fn hopper_plus_tree_size() {
+        for chipset in [Chipset::GH100, Chipset::GB100, Chipset::GB202] {
+            assert_eq!(cpu_interrupt_hal(chipset).leaf_count(), LeafCount::Sixteen);
+        }
+    }
+
+    /// Only pre-Hopper MSI rearms through the configuration-space mirror. MSI on Hopper and later
+    /// cycles the `TOP` enables of every serviced subtree.
+    #[test]
+    fn msi_rearm_method_per_arch() {
+        for chipset in [Chipset::TU102, Chipset::GA102, Chipset::AD102] {
+            let hal = cpu_interrupt_hal(chipset);
+            assert_eq!(
+                hal.pci_irq_rearm_method(MsiType::Msi),
+                PciIrqRearmMethod::ConfigMirrorEoi
+            );
+        }
+
+        for chipset in [Chipset::GH100, Chipset::GB100, Chipset::GB202] {
+            let hal = cpu_interrupt_hal(chipset);
+            assert_eq!(
+                hal.pci_irq_rearm_method(MsiType::Msi),
+                PciIrqRearmMethod::TopEnableCycleServiced
+            );
+        }
+    }
+
+    /// MSI-X gives each subtree its own table entry, so on every architecture its rearm cycles
+    /// only the subtree the handler serves.
+    #[test]
+    fn msix_rearms_one_subtree_on_every_arch() {
+        for chipset in [
+            Chipset::TU102,
+            Chipset::GA102,
+            Chipset::AD102,
+            Chipset::GH100,
+            Chipset::GB100,
+            Chipset::GB202,
+        ] {
+            let hal = cpu_interrupt_hal(chipset);
+            assert_eq!(
+                hal.pci_irq_rearm_method(MsiType::MsiX),
+                PciIrqRearmMethod::TopEnableCycleSubtree
+            );
+        }
+    }
+}
diff --git a/drivers/gpu/nova-core/irq/interrupt_tree.rs b/drivers/gpu/nova-core/irq/interrupt_tree.rs
index 62c0bbda61b2..a6da9900f9da 100644
--- a/drivers/gpu/nova-core/irq/interrupt_tree.rs
+++ b/drivers/gpu/nova-core/irq/interrupt_tree.rs
@@ -531,3 +531,134 @@ fn drop(&mut self) {
         clear_top_enables(self.bar, self.serviced);
     }
 }
+
+#[kunit_tests(nova_core_gin_tree)]
+mod tests {
+    use super::*;
+
+    /// A leaf index is a `Bounded<usize, 4>`, so it accepts 0..=15 and rejects 16.
+    #[test]
+    fn leaf_index_bounds() {
+        assert!(LeafIndex::try_new(0).is_some());
+        assert!(LeafIndex::try_new(15).is_some());
+        assert!(LeafIndex::try_new(16).is_none());
+    }
+
+    /// A leaf count yields one subtree per pair of leaves, and 32 vectors per leaf.
+    #[test]
+    fn leaf_count_derives_subtrees_and_vectors() {
+        assert_eq!(LeafCount::Eight.subtree_count(), 4);
+        assert_eq!(
+            Bounded::<u32, 32>::from(LeafCount::Eight.subtree_set()).get(),
+            0x0f
+        );
+        assert_eq!(LeafCount::Eight.vector_count(), 256);
+
+        assert_eq!(LeafCount::Sixteen.subtree_count(), 8);
+        assert_eq!(
+            Bounded::<u32, 32>::from(LeafCount::Sixteen.subtree_set()).get(),
+            0xff
+        );
+        assert_eq!(LeafCount::Sixteen.vector_count(), 512);
+    }
+
+    /// A tree enumerates every leaf it implements, in order, and no more.
+    #[test]
+    fn implemented_leaves_covers_the_tree() {
+        for (count, expected) in [(LeafCount::Eight, 8usize), (LeafCount::Sixteen, 16)] {
+            let mut seen = 0;
+
+            for (index, leaf) in implemented_leaves(count).enumerate() {
+                assert_eq!(leaf.get(), index);
+                seen += 1;
+            }
+
+            assert_eq!(seen, expected);
+        }
+    }
+
+    /// A vector maps to its leaf, its bit within that leaf, and its subtree. The fixed doorbell
+    /// (129) and GSP (155) vectors share a subtree, so one allocation and one enabled subtree
+    /// serve both.
+    #[test]
+    fn vector_maps_to_leaf_bit_and_subtree() {
+        let doorbell = GinVector::new::<129>();
+        let gsp = GinVector::new::<155>();
+
+        assert_eq!(doorbell.leaf_index().get(), 4);
+        assert_eq!(doorbell.leaf_mask().into_raw(), 1 << 1);
+        assert_eq!(doorbell.subtree().index(), 2);
+
+        assert_eq!(gsp.leaf_index().get(), 4);
+        assert_eq!(gsp.leaf_mask().into_raw(), 1 << 27);
+        assert_eq!(gsp.subtree().index(), 2);
+
+        assert_eq!(doorbell.subtree(), gsp.subtree());
+    }
+
+    /// Both fixed vectors lie within the 8-leaf tree, so every supported part carries them.
+    #[test]
+    fn fixed_vectors_fit_the_narrowest_tree() {
+        assert!(GinVector::new::<129>().validate(LeafCount::Eight).is_ok());
+        assert!(GinVector::new::<155>().validate(LeafCount::Eight).is_ok());
+
+        // The first vector beyond an 8-leaf tree.
+        assert!(GinVector::new::<256>().validate(LeafCount::Eight).is_err());
+        assert!(GinVector::new::<256>().validate(LeafCount::Sixteen).is_ok());
+    }
+
+    /// A subtree set reports membership, intersection, and how far it extends from subtree 0.
+    #[test]
+    fn subtree_set_operations() {
+        let gsp = GinVector::new::<155>().subtree();
+
+        assert!(LeafCount::Eight.subtree_set().contains(gsp));
+        assert!(!LeafCount::Eight.subtree_set().is_empty());
+
+        // Subtree 2 is the highest the GSP needs, so an MSI-X request covers entries 0 through 2.
+        assert_eq!(SubtreeSet::from(gsp).span(), 3);
+
+        // Hopper implements every subtree an 8-leaf tree does.
+        assert_eq!(
+            LeafCount::Sixteen
+                .subtree_set()
+                .intersection(LeafCount::Eight.subtree_set()),
+            LeafCount::Eight.subtree_set()
+        );
+    }
+
+    /// Iterating a subtree set yields each of its subtrees once, lowest index first, and yields
+    /// nothing for an empty set.
+    #[test]
+    fn subtree_set_iterates_its_members() {
+        assert!(LeafCount::Eight
+            .subtree_set()
+            .iter()
+            .map(Subtree::index)
+            .eq([0u32, 1, 2, 3]));
+
+        let gsp = SubtreeSet::from(GinVector::new::<155>().subtree());
+        assert!(gsp.iter().map(Subtree::index).eq([2u32]));
+
+        let empty = SubtreeSet::from(Bounded::<u32, 32>::new::<0>());
+        assert_eq!(empty.iter().count(), 0);
+    }
+
+    /// Every supported chipset implements the subtree that carries the GSP notification.
+    #[test]
+    fn gsp_subtree_is_implemented_everywhere() {
+        for chipset in [
+            Chipset::TU102,
+            Chipset::GA102,
+            Chipset::AD102,
+            Chipset::GH100,
+            Chipset::GB100,
+            Chipset::GB202,
+        ] {
+            assert!(cpu_interrupt_hal(chipset)
+                .leaf_count()
+                .subtree_set()
+                .contains(crate::irq::gsp::GSP_SUBTREE));
+        }
+    }
+}
-- 
2.55.0