[PATCH v4 6/8] drm/xe/madvise: Implement per-VMA purgeable state tracking

Arvind Yadav
2026-01-20T06:09:28Z

Track purgeable state per-VMA instead of using a coarse shared
BO check. This prevents purging shared BOs until all VMAs across
all VMs are marked DONTNEED.

Add xe_bo_all_vmas_dontneed() to check all VMAs before marking
a BO purgeable. Add xe_bo_recheck_purgeable_on_vma_unbind() to
handle state transitions when VMAs are destroyed - if all
remaining VMAs are DONTNEED the BO can become purgeable, or if
no VMAs remain it transitions to WILLNEED.

The per-VMA purgeable_state field stores the madvise hint for
each mapping. Shared BOs can only be purged when all VMAs
unanimously indicate DONTNEED.

v3:
- This addresses Thomas Hellström's feedback: "loop over all vmas
attached to the bo and check that they all say WONTNEED. This will
also need a check at VMA unbinding"

v4:
- @madv_purgeable atomic_t → u32 change across all relevant patches. (Matt)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
drivers/gpu/drm/xe/xe_vm.c | 15 +++++-
drivers/gpu/drm/xe/xe_vm_madvise.c | 84 +++++++++++++++++++++++++++++-
drivers/gpu/drm/xe/xe_vm_madvise.h | 3 ++
drivers/gpu/drm/xe/xe_vm_types.h | 11 ++++
4 files changed, 111 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index f250daae3012..9543960b5613 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -40,6 +40,7 @@
#include "xe_tile.h"
#include "xe_tlb_inval.h"
#include "xe_trace_bo.h"
+#include "xe_vm_madvise.h"
#include "xe_wa.h"

static struct drm_gem_object *xe_vm_obj(struct xe_vm *vm)
@@ -1079,12 +1080,18 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
static void xe_vma_destroy_late(struct xe_vma *vma)
{
struct xe_vm *vm = xe_vma_vm(vma);
+ struct xe_bo *bo = NULL;

if (vma->ufence) {
xe_sync_ufence_put(vma->ufence);
vma->ufence = NULL;
}

+ /* Get BO reference for purgeable state re-check */
+ if (!xe_vma_is_userptr(vma) && !xe_vma_is_null(vma) &&
+ !xe_vma_is_cpu_addr_mirror(vma))
+ bo = xe_vma_bo(vma);
+
if (xe_vma_is_userptr(vma)) {
struct xe_userptr_vma *uvma = to_userptr_vma(vma);

@@ -1093,7 +1100,13 @@ static void xe_vma_destroy_late(struct xe_vma *vma)
} else if (xe_vma_is_null(vma) || xe_vma_is_cpu_addr_mirror(vma)) {
xe_vm_put(vm);
} else {
- xe_bo_put(xe_vma_bo(vma));
+ /* Trylock safe for async context; madvise corrects failures */
+ if (bo && dma_resv_trylock(bo->ttm.base.resv)) {
+ xe_bo_recheck_purgeable_on_vma_unbind(bo);
+ dma_resv_unlock(bo->ttm.base.resv);
+ }
+
+ xe_bo_put(bo);
}

xe_vma_free(vma);
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index dfeab9e24a09..27b6ad65b314 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -12,6 +12,7 @@
#include "xe_pat.h"
#include "xe_pt.h"
#include "xe_svm.h"
+#include "xe_vm.h"

struct xe_vmas_in_madvise_range {
u64 addr;
@@ -179,6 +180,80 @@ static void madvise_pat_index(struct xe_device *xe, struct xe_vm *vm,
}
}

+/**
+ * xe_bo_all_vmas_dontneed() - Check if all VMAs of a BO are marked DONTNEED
+ * @bo: Buffer object
+ *
+ * Check all VMAs across all VMs to determine if BO can be purged.
+ * Shared BOs require unanimous DONTNEED state from all mappings.
+ *
+ * Caller must hold BO dma-resv lock.
+ *
+ * Return: true if all VMAs are DONTNEED, false otherwise
+ */
+static bool xe_bo_all_vmas_dontneed(struct xe_bo *bo)
+{
+ struct drm_gpuvm_bo *vm_bo;
+ struct drm_gpuva *gpuva;
+ struct drm_gem_object *obj = &bo->ttm.base;
+ bool has_vmas = false;
+
+ dma_resv_assert_held(bo->ttm.base.resv);
+
+ drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
+ drm_gpuvm_bo_for_each_va(gpuva, vm_bo) {
+ struct xe_vma *vma = gpuva_to_vma(gpuva);
+
+ has_vmas = true;
+
+ /* Any non-DONTNEED VMA prevents purging */
+ if (READ_ONCE(vma->purgeable_state) != XE_MADV_PURGEABLE_DONTNEED)
+ return false;
+ }
+ }
+
+ /* No VMAs means not purgeable */
+ if (!has_vmas)
+ return false;
+
+ return true;
+}
+
+/**
+ * xe_bo_recheck_purgeable_on_vma_unbind() - Re-evaluate BO purgeable state after VMA unbind
+ * @bo: Buffer object
+ *
+ * When a VMA is unbound, re-check if the BO's purgeable state should change.
+ * Destroyed VMAs may allow the BO to become purgeable if all remaining VMAs
+ * are DONTNEED, or require transition to WILLNEED if no VMAs remain.
+ *
+ * Called from VMA destruction path with BO dma-resv lock held.
+ */
+void xe_bo_recheck_purgeable_on_vma_unbind(struct xe_bo *bo)
+{
+ if (!bo)
+ return;
+
+ dma_resv_assert_held(bo->ttm.base.resv);
+
+ /*
+ * Once purged, always purged. Cannot transition back to WILLNEED.
+ * This matches i915 semantics where purged BOs are permanently invalid.
+ */
+ if (bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED)
+ return;
+
+ if (xe_bo_all_vmas_dontneed(bo)) {
+ /* All VMAs are DONTNEED - mark BO purgeable */
+ if (bo->madv_purgeable != XE_MADV_PURGEABLE_DONTNEED)
+ bo->madv_purgeable = XE_MADV_PURGEABLE_DONTNEED;
+ } else {
+ /* At least one VMA is WILLNEED - BO must not be purgeable */
+ if (bo->madv_purgeable != XE_MADV_PURGEABLE_WILLNEED)
+ bo->madv_purgeable = XE_MADV_PURGEABLE_WILLNEED;
+ }
+}
+
/*
* Handle purgeable buffer object advice for DONTNEED/WILLNEED/PURGED.
* Returns true if any BO was purged, false otherwise.
@@ -213,10 +288,17 @@ static bool xe_vm_madvise_purgeable_bo(struct xe_device *xe, struct xe_vm *vm,

switch (op->purge_state_val.val) {
case DRM_XE_VMA_PURGEABLE_STATE_WILLNEED:
+ vmas[i]->purgeable_state = XE_MADV_PURGEABLE_WILLNEED;
+
+ /* Mark VMA WILLNEED - BO becomes non-purgeable immediately */
bo->madv_purgeable = XE_MADV_PURGEABLE_WILLNEED;
break;
case DRM_XE_VMA_PURGEABLE_STATE_DONTNEED:
- bo->madv_purgeable = XE_MADV_PURGEABLE_DONTNEED;
+ vmas[i]->purgeable_state = XE_MADV_PURGEABLE_DONTNEED;
+
+ /* Mark BO purgeable only if all VMAs are DONTNEED */
+ if (xe_bo_all_vmas_dontneed(bo))
+ bo->madv_purgeable = XE_MADV_PURGEABLE_DONTNEED;
break;
default:
drm_warn(&vm->xe->drm, "Invalid madvice value = %d\n",
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.h b/drivers/gpu/drm/xe/xe_vm_madvise.h
index b0e1fc445f23..61868f851949 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.h
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.h
@@ -8,8 +8,11 @@

struct drm_device;
struct drm_file;
+struct xe_bo;

int xe_vm_madvise_ioctl(struct drm_device *dev, void *data,
struct drm_file *file);

+void xe_bo_recheck_purgeable_on_vma_unbind(struct xe_bo *bo);
+
#endif
diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
index 437f64202f3b..94ca9d033b06 100644
--- a/drivers/gpu/drm/xe/xe_vm_types.h
+++ b/drivers/gpu/drm/xe/xe_vm_types.h
@@ -150,6 +150,17 @@ struct xe_vma {
*/
bool skip_invalidation;

+ /**
+ * @purgeable_state: Purgeable hint for this VMA mapping
+ *
+ * Per-VMA purgeable state from madvise. Valid states are WILLNEED (0)
+ * or DONTNEED (1). Shared BOs require all VMAs to be DONTNEED before
+ * the BO can be purged. PURGED state exists only at BO level.
+ *
+ * Protected by BO dma-resv lock. Set via DRM_IOCTL_XE_MADVISE.
+ */
+ u32 purgeable_state;
+
/**
* @ufence: The user fence that was provided with MAP.
* Needs to be signalled before UNMAP can be processed.
--
2.43.0