drm/xe: convert PCI barrier mmap to use xe_mmio_gem

Convert the PCI barrier mmap over to use xe_mmio_gem, which is a good
match for this functionality. This has the following advantages:

 1. Removes a bunch of code.
 2. Replaces the fragile hard coded fake offset design.
 3. Adds the first user for xe_mmio_gem, which is preferred over nuking
    it. There are also potentially other upcoming usecases wanting this
    type of functionality, so having standard component to do this would
    be good.

There shouldn't be any big functional change here. From userspace pov,
they still query the fake offset like before, just that now it is no
longer hard coded in the KMD.

v2 (Thomas):
  - Prefer scoped_guard(). Also, just annotate ALL locations, even if
    not strictly needed. Reflect that in the kernel-doc. This will also
    shut up static analysis tools.

Assisted-by: LLM
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Tejas Upadhyay <tejas.upadhyay@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Ilia Levi <ilia.levi@intel.com>
Reviewed-by: Ilia Levi <ilia.levi@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20260908165046.1393557-18-matthew.auld@intel.com

4 files changed, 61 insertions, 110 deletions

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index b162753cebb7..9f3f0cb95afa 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -28,6 +28,7 @@
 #include "xe_ggtt.h"
 #include "xe_map.h"
 #include "xe_migrate.h"
+#include "xe_mmio_gem.h"
 #include "xe_pat.h"
 #include "xe_pm.h"
 #include "xe_preempt_fence.h"
@@ -3664,6 +3665,39 @@ out_vm:
 	return err;
 }
 
+static int xe_gem_pci_barrier_mmap_offset(struct xe_device *xe, struct drm_file *file,
+					  struct drm_xe_gem_mmap_offset *args)
+{
+	struct xe_file *xef = file->driver_priv;
+	struct xe_mmio_gem **barrier = &xef->mmio_gem.pci_barrier;
+
+	if (XE_IOCTL_DBG(xe, !IS_DGFX(xe)))
+		return -EINVAL;
+
+	if (XE_IOCTL_DBG(xe, args->handle))
+		return -EINVAL;
+
+	scoped_guard(mutex, &xef->mmio_gem.lock) {
+		if (!*barrier) {
+			phys_addr_t phys_addr;
+
+#define LAST_DB_PAGE_OFFSET 0x7ff000
+			phys_addr = pci_resource_start(to_pci_dev(xe->drm.dev), 0) +
+				LAST_DB_PAGE_OFFSET;
+			*barrier = xe_mmio_gem_create(xe, file, phys_addr, SZ_4K);
+			if (IS_ERR(*barrier)) {
+				int err = PTR_ERR(*barrier);
+
+				*barrier = NULL;
+				return err;
+			}
+		}
+
+		args->offset = xe_mmio_gem_mmap_offset(*barrier);
+	}
+	return 0;
+}
+
 int xe_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
 			     struct drm_file *file)
 {
@@ -3679,21 +3713,8 @@ int xe_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
 			 ~DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER))
 		return -EINVAL;
 
-	if (args->flags & DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER) {
-		if (XE_IOCTL_DBG(xe, !IS_DGFX(xe)))
-			return -EINVAL;
-
-		if (XE_IOCTL_DBG(xe, args->handle))
-			return -EINVAL;
-
-		if (XE_IOCTL_DBG(xe, PAGE_SIZE > SZ_4K))
-			return -EINVAL;
-
-		BUILD_BUG_ON(((XE_PCI_BARRIER_MMAP_OFFSET >> XE_PTE_SHIFT) +
-			      SZ_4K) >= DRM_FILE_PAGE_OFFSET_START);
-		args->offset = XE_PCI_BARRIER_MMAP_OFFSET;
-		return 0;
-	}
+	if (args->flags & DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER)
+		return xe_gem_pci_barrier_mmap_offset(xe, file, args);
 
 	gem_obj = drm_gem_object_lookup(file, args->handle);
 	if (XE_IOCTL_DBG(xe, !gem_obj))
diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index eede678ad303..290ca624e2a7 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -87,7 +87,6 @@
 
 #define XE_BO_PROPS_INVALID	(-1)
 
-#define XE_PCI_BARRIER_MMAP_OFFSET	(0x50 << XE_PTE_SHIFT)
 
 /**
  * enum xe_madv_purgeable_state - Buffer object purgeable state enumeration
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 8583b2e9ecf4..205cb4e7f9e8 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -50,6 +50,7 @@
 #include "xe_late_bind_fw.h"
 #include "xe_log.h"
 #include "xe_mmio.h"
+#include "xe_mmio_gem.h"
 #include "xe_module.h"
 #include "xe_nvm.h"
 #include "xe_oa.h"
@@ -111,6 +112,8 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 	mutex_init(&xef->exec_queue.lock);
 	xa_init_flags(&xef->exec_queue.xa, XA_FLAGS_ALLOC1);
 
+	mutex_init(&xef->mmio_gem.lock);
+
 	file->driver_priv = xef;
 	kref_init(&xef->refcount);
 
@@ -133,6 +136,8 @@ static void xe_file_destroy(struct kref *ref)
 	xa_destroy(&xef->vm.xa);
 	mutex_destroy(&xef->vm.lock);
 
+	mutex_destroy(&xef->mmio_gem.lock);
+
 	xe_drm_client_put(xef->client);
 	kfree(xef->process_name);
 	kfree(xef);
@@ -189,6 +194,13 @@ static void xe_file_close(struct drm_device *dev, struct drm_file *file)
 	xa_for_each(&xef->vm.xa, idx, vm)
 		xe_vm_close_and_put(vm);
 
+	scoped_guard(mutex, &xef->mmio_gem.lock) {
+		if (xef->mmio_gem.pci_barrier) {
+			xe_mmio_gem_destroy(xef->mmio_gem.pci_barrier, file);
+			xef->mmio_gem.pci_barrier = NULL;
+		}
+	}
+
 	xe_file_put(xef);
 }
 
@@ -258,95 +270,6 @@ static long xe_drm_compat_ioctl(struct file *file, unsigned int cmd, unsigned lo
 #define xe_drm_compat_ioctl NULL
 #endif
 
-static void barrier_open(struct vm_area_struct *vma)
-{
-	drm_dev_get(vma->vm_private_data);
-}
-
-static void barrier_close(struct vm_area_struct *vma)
-{
-	drm_dev_put(vma->vm_private_data);
-}
-
-static void barrier_release_dummy_page(struct drm_device *dev, void *res)
-{
-	struct page *dummy_page = (struct page *)res;
-
-	__free_page(dummy_page);
-}
-
-static vm_fault_t barrier_fault(struct vm_fault *vmf)
-{
-	struct drm_device *dev = vmf->vma->vm_private_data;
-	struct vm_area_struct *vma = vmf->vma;
-	vm_fault_t ret = VM_FAULT_NOPAGE;
-	pgprot_t prot;
-	int idx;
-
-	prot = vma_get_page_prot(vma);
-
-	if (drm_dev_enter(dev, &idx)) {
-		unsigned long pfn;
-
-#define LAST_DB_PAGE_OFFSET 0x7ff001
-		pfn = PHYS_PFN(pci_resource_start(to_pci_dev(dev->dev), 0) +
-				LAST_DB_PAGE_OFFSET);
-		ret = vmf_insert_pfn_prot(vma, vma->vm_start, pfn,
-					  pgprot_noncached(prot));
-		drm_dev_exit(idx);
-	} else {
-		struct page *page;
-
-		/* Allocate new dummy page to map all the VA range in this VMA to it*/
-		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
-		if (!page)
-			return VM_FAULT_OOM;
-
-		/* Set the page to be freed using drmm release action */
-		if (drmm_add_action_or_reset(dev, barrier_release_dummy_page, page))
-			return VM_FAULT_OOM;
-
-		ret = vmf_insert_pfn_prot(vma, vma->vm_start, page_to_pfn(page),
-					  prot);
-	}
-
-	return ret;
-}
-
-static const struct vm_operations_struct vm_ops_barrier = {
-	.open = barrier_open,
-	.close = barrier_close,
-	.fault = barrier_fault,
-};
-
-static int xe_pci_barrier_mmap(struct file *filp,
-			       struct vm_area_struct *vma)
-{
-	struct drm_file *priv = filp->private_data;
-	struct drm_device *dev = priv->minor->dev;
-	struct xe_device *xe = to_xe_device(dev);
-
-	if (!IS_DGFX(xe))
-		return -EINVAL;
-
-	if (vma->vm_end - vma->vm_start > SZ_4K)
-		return -EINVAL;
-
-	if (vma_is_cow_mapping(vma))
-		return -EINVAL;
-
-	if (vma->vm_flags & (VM_READ | VM_EXEC))
-		return -EINVAL;
-
-	vm_flags_clear(vma, VM_MAYREAD | VM_MAYEXEC);
-	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP | VM_IO);
-	vma->vm_ops = &vm_ops_barrier;
-	vma->vm_private_data = dev;
-	drm_dev_get(vma->vm_private_data);
-
-	return 0;
-}
-
 static int xe_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct drm_file *priv = filp->private_data;
@@ -355,11 +278,6 @@ static int xe_mmap(struct file *filp, struct vm_area_struct *vma)
 	if (drm_dev_is_unplugged(dev))
 		return -ENODEV;
 
-	switch (vma->vm_pgoff) {
-	case XE_PCI_BARRIER_MMAP_OFFSET >> XE_PTE_SHIFT:
-		return xe_pci_barrier_mmap(filp, vma);
-	}
-
 	return drm_gem_mmap(filp, vma);
 }
 
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 180d450a6deb..f88bacf63c83 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -40,6 +40,7 @@ struct intel_display;
 struct intel_dg_nvm_dev;
 struct xe_ggtt;
 struct xe_i2c;
+struct xe_mmio_gem;
 struct xe_pat_ops;
 struct xe_pxp;
 struct xe_ttm_stolen_mgr;
@@ -676,6 +677,18 @@ struct xe_file {
 
 	/** @refcount: ref count of this xe file */
 	struct kref refcount;
+
+	/** @mmio_gem: MMIO GEM objects for this xe file */
+	struct {
+		/**
+		 * @mmio_gem.lock: Protects allocation and attach of MMIO
+		 * GEM objects on first use (singleton). All MMIO GEM access
+		 * should be guarded by this lock. Prefer scoped_guard().
+		 */
+		struct mutex lock;
+		/** @mmio_gem.pci_barrier: MMIO GEM object for PCI barrier mmap. */
+		struct xe_mmio_gem *pci_barrier;
+	} mmio_gem;
 };
 
 #endif