[PATCH 0/2] drm/gpuvm: add debugfs utilities for GPU VA state dumping

[PATCH 0/2] drm/gpuvm: add debugfs utilities for GPU VA state dumping

[Alvin Sun]

This patch series adds helper APIs to enable GPU drivers to implement
debugfs interfaces [1] [2] that expose GPU VA mapping state for
inspection and debugging purposes.

Dependencies:
- [PATCH v12 0/1] rust: interop: Add list module for C linked list interface
https://lore.kernel.org/rust-for-linux/20260306203648.1136554-1-joelagnelf@nvidia.com/
- [PATCH v4 0/6] Rust GPUVM immediate mode
https://lore.kernel.org/rust-for-linux/20260130-gpuvm-rust-v4-0-8364d104ff40@google.com/

Link: https://gitlab.freedesktop.org/panfrost/linux/-/issues/11 [1]
Link: https://gitlab.freedesktop.org/panfrost/linux/-/merge_requests/59 [2]
Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
Alvin Sun (2):
      drm/gpuvm: add name(), RawGpuVa and kernel_alloc_va() for debugfs
      drm/gpuvm: add GpuVaIter and va_mappings() for debugfs

 rust/kernel/drm/gpuvm/mod.rs | 20 ++++++++++
 rust/kernel/drm/gpuvm/va.rs  | 90 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)
---
base-commit: 34cb4f916af10153c87fabaf6c34e4cafa170427
change-id: 20260317-gpuvm-helpers-28dbe2b303b2
prerequisite-change-id: 20251128-gpuvm-rust-b719cac27ad6:v4
prerequisite-patch-id: 94679c36e594a7d6fc9279dad5419f5558f2302b
prerequisite-patch-id: 03b672e1e2c07d677326d64de7fccc6092ea6812
prerequisite-patch-id: 3c1a4c6eec5faaa1a70de53581bd7ae5ab7bc324
prerequisite-patch-id: 3712380c7bfdf784b6aca146864576cd76bc9a72
prerequisite-patch-id: 3149e1016beefce815c860d4b64e7c1bb7589f15
prerequisite-patch-id: 23467ae9a31746a6c44678e0054f1442c6a5ac06
prerequisite-message-id: <<20260306203648.1136554-1-joelagnelf@nvidia.com>>
prerequisite-patch-id: 9bc17713af35e5f2744ac55157e2b5078eae77cc

Best regards,
-- 
Alvin Sun <alvin.sun@linux.dev>

[PATCH 1/2] drm/gpuvm: add name(), RawGpuVa and kernel_alloc_va() for debugfs

[Alvin Sun]

Expose GPU VM name and kernel-reserved VA so drivers can dump GPU VA
state in debugfs.

Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
 rust/kernel/drm/gpuvm/mod.rs | 14 ++++++++++++++
 rust/kernel/drm/gpuvm/va.rs  | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/rust/kernel/drm/gpuvm/mod.rs b/rust/kernel/drm/gpuvm/mod.rs
index 20e512842dfc6..3186df9f740cf 100644
--- a/rust/kernel/drm/gpuvm/mod.rs
+++ b/rust/kernel/drm/gpuvm/mod.rs
@@ -165,6 +165,13 @@ pub fn as_raw(&self) -> *mut bindings::drm_gpuvm {
         self.vm.get()
     }
 
+    /// Returns the name of this GpuVm.
+    #[inline]
+    pub fn name(&self) -> &CStr {
+        // SAFETY: The `name` field is immutable and points to a NUL-terminated string.
+        unsafe { CStr::from_char_ptr((*self.as_raw()).name) }
+    }
+
     /// The start of the VA space.
     #[inline]
     pub fn va_start(&self) -> u64 {
@@ -188,6 +195,13 @@ pub fn va_range(&self) -> Range<u64> {
         Range { start, end }
     }
 
+    /// Returns the kernel-allocated VA for this GpuVm.
+    #[inline]
+    pub fn kernel_alloc_va(&self) -> &RawGpuVa {
+        // SAFETY: The `self.as_raw()` is guaranteed to be a valid pointer to a drm_gpuvm.
+        unsafe { RawGpuVa::from_raw(&raw mut (*self.as_raw()).kernel_alloc_node) }
+    }
+
     /// Get or create the [`GpuVmBo`] for this gem object.
     #[inline]
     pub fn obtain(
diff --git a/rust/kernel/drm/gpuvm/va.rs b/rust/kernel/drm/gpuvm/va.rs
index a31122ff22282..8b8fd500b3c5f 100644
--- a/rust/kernel/drm/gpuvm/va.rs
+++ b/rust/kernel/drm/gpuvm/va.rs
@@ -81,6 +81,43 @@ pub fn vm_bo(&self) -> &GpuVmBo<T> {
     }
 }
 
+/// Represents that a range of a GEM object is mapped in the kernel.
+#[repr(transparent)]
+pub struct RawGpuVa(Opaque<bindings::drm_gpuva>);
+
+impl RawGpuVa {
+    /// Access this [`RawGpuVa`] from a raw pointer.
+    ///
+    /// # Safety
+    ///
+    /// For the duration of `'a`, the pointer must reference a valid `drm_gpuva`.
+    #[inline]
+    pub unsafe fn from_raw<'a>(ptr: *mut bindings::drm_gpuva) -> &'a Self {
+        // SAFETY: `drm_gpuva` and `RawGpuVa` have the same layout.
+        unsafe { &*(ptr.cast()) }
+    }
+
+    /// Returns a raw pointer to underlying C value.
+    #[inline]
+    pub fn as_raw(&self) -> *mut bindings::drm_gpuva {
+        self.0.get()
+    }
+
+    /// Returns the address of this mapping in the GPU virtual address space.
+    #[inline]
+    pub fn addr(&self) -> u64 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a valid pointer to a `drm_gpuva`.
+        unsafe { (*self.as_raw()).va.addr }
+    }
+
+    /// Returns the length of this mapping.
+    #[inline]
+    pub fn length(&self) -> u64 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a valid pointer to a `drm_gpuva`.
+        unsafe { (*self.as_raw()).va.range }
+    }
+}
+
 /// A pre-allocated [`GpuVa`] object.
 ///
 /// # Invariants

-- 
2.43.0

[PATCH 2/2] drm/gpuvm: add GpuVaIter and va_mappings() for debugfs

[Alvin Sun]

Add an iterator over VA mappings so drivers can walk and dump GPU VA
state in debugfs.

Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
 rust/kernel/drm/gpuvm/mod.rs |  6 +++++
 rust/kernel/drm/gpuvm/va.rs  | 53 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/rust/kernel/drm/gpuvm/mod.rs b/rust/kernel/drm/gpuvm/mod.rs
index 3186df9f740cf..41b99d468f9d9 100644
--- a/rust/kernel/drm/gpuvm/mod.rs
+++ b/rust/kernel/drm/gpuvm/mod.rs
@@ -301,6 +301,12 @@ pub fn data(&mut self) -> &mut T {
         // SAFETY: By the type invariants we may access `core`.
         unsafe { &mut *self.0.data.get() }
     }
+
+    /// Returns an iterator over the VA mappings in this GpuVm.
+    #[inline]
+    pub fn va_mappings(&self) -> GpuVaIter<'_, T> {
+        GpuVaIter::new(&self.0)
+    }
 }
 
 impl<T: DriverGpuVm> Deref for GpuVmCore<T> {
diff --git a/rust/kernel/drm/gpuvm/va.rs b/rust/kernel/drm/gpuvm/va.rs
index 8b8fd500b3c5f..3210047f880e3 100644
--- a/rust/kernel/drm/gpuvm/va.rs
+++ b/rust/kernel/drm/gpuvm/va.rs
@@ -1,6 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0 OR MIT
 
 use super::*;
+use crate::interop::list::{
+    CList,
+    CListIter, //
+};
+use core::{
+    marker::PhantomData,
+    mem::offset_of, //
+};
 
 /// Represents that a range of a GEM object is mapped in this [`GpuVm`] instance.
 ///
@@ -118,6 +126,51 @@ pub fn length(&self) -> u64 {
     }
 }
 
+const DRM_GPUVA_LIST_ENTRY_OFFSET: usize = offset_of!(bindings::drm_gpuva, rb.entry);
+type RawGpuVaIter<'a> = CListIter<'a, RawGpuVa, DRM_GPUVA_LIST_ENTRY_OFFSET>;
+
+/// An iterator over the VA mappings in a [`GpuVm`].
+pub struct GpuVaIter<'a, T: DriverGpuVm> {
+    raw_gpuva_iter: RawGpuVaIter<'a>,
+    kern_gpuva_ptr: *mut bindings::drm_gpuva,
+    _marker: PhantomData<&'a T>,
+}
+
+impl<'a, T: DriverGpuVm> GpuVaIter<'a, T> {
+    #[inline]
+    pub(crate) fn new(gpuvm: &'a GpuVm<T>) -> Self {
+        // SAFETY: `gpuvm` is valid.
+        let head = unsafe { &raw mut (*gpuvm.as_raw()).rb.list };
+        // SAFETY: `head` is a valid pointer to a drm_gpuva list head.
+        let clist = unsafe { CList::<RawGpuVa, DRM_GPUVA_LIST_ENTRY_OFFSET>::from_raw(head) };
+        let kern_gpuva_ptr = gpuvm.kernel_alloc_va().as_raw();
+
+        Self {
+            raw_gpuva_iter: clist.iter(),
+            kern_gpuva_ptr,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<'a, T: DriverGpuVm> Iterator for GpuVaIter<'a, T> {
+    type Item = &'a GpuVa<T>;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut curr = self.raw_gpuva_iter.next()?;
+
+        if curr.as_raw() == self.kern_gpuva_ptr {
+            // Skip kernel reserved node.
+            curr = self.raw_gpuva_iter.next()?;
+        }
+
+        // SAFETY: We have skipped the kernel reserved node, all remaining
+        // entries are valid GpuVa<T> instances.
+        Some(unsafe { GpuVa::from_raw(curr.as_raw()) })
+    }
+}
+
 /// A pre-allocated [`GpuVa`] object.
 ///
 /// # Invariants

-- 
2.43.0