drm/nouveau: Fixup gk20a instobj hierarchy

Commit 12c9b05d ("drm/nouveau/imem: support allocations not
preserved across suspend") uses container_of() to cast from struct
nvkm_memory to struct nvkm_instobj, assuming that all instance objects
are derived from struct nvkm_instobj. For the gk20a family that's not
the case and they are derived from struct nvkm_memory instead. This
causes some subtle data corruption (nvkm_instobj.preserve ends up
mapping to gk20a_instobj.vaddr) that causes a NULL pointer dereference
in gk20a_instobj_acquire_iommu() (and possibly elsewhere) and also
prevents suspend/resume from working.

Fix this by making struct gk20a_instobj derive from struct nvkm_instobj
instead.

Fixes: 12c9b05d ("drm/nouveau/imem: support allocations not preserved across suspend")
Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231208104653.1917055-1-thierry.reding@gmail.com

drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c

@@ -49,14 +49,14 @@
 #include <subdev/mmu.h>
 
 struct gk20a_instobj {
-	struct nvkm_memory memory;
+	struct nvkm_instobj base;
 	struct nvkm_mm_node *mn;
 	struct gk20a_instmem *imem;
 
 	/* CPU mapping */
 	u32 *vaddr;
 };
-#define gk20a_instobj(p) container_of((p), struct gk20a_instobj, memory)
+#define gk20a_instobj(p) container_of((p), struct gk20a_instobj, base.memory)
 
 /*
  * Used for objects allocated using the DMA API
@@ -148,7 +148,7 @@ gk20a_instobj_iommu_recycle_vaddr(struct gk20a_instobj_iommu *obj)
 	list_del(&obj->vaddr_node);
 	vunmap(obj->base.vaddr);
 	obj->base.vaddr = NULL;
-	imem->vaddr_use -= nvkm_memory_size(&obj->base.memory);
+	imem->vaddr_use -= nvkm_memory_size(&obj->base.base.memory);
 	nvkm_debug(&imem->base.subdev, "vaddr used: %x/%x\n", imem->vaddr_use,
 		   imem->vaddr_max);
 }
@@ -283,7 +283,7 @@ gk20a_instobj_map(struct nvkm_memory *memory, u64 offset, struct nvkm_vmm *vmm,
 {
 	struct gk20a_instobj *node = gk20a_instobj(memory);
 	struct nvkm_vmm_map map = {
-		.memory = &node->memory,
+		.memory = &node->base.memory,
 		.offset = offset,
 		.mem = node->mn,
 	};
@@ -391,8 +391,8 @@ gk20a_instobj_ctor_dma(struct gk20a_instmem *imem, u32 npages, u32 align,
 		return -ENOMEM;
 	*_node = &node->base;
 
-	nvkm_memory_ctor(&gk20a_instobj_func_dma, &node->base.memory);
-	node->base.memory.ptrs = &gk20a_instobj_ptrs;
+	nvkm_memory_ctor(&gk20a_instobj_func_dma, &node->base.base.memory);
+	node->base.base.memory.ptrs = &gk20a_instobj_ptrs;
 
 	node->base.vaddr = dma_alloc_attrs(dev, npages << PAGE_SHIFT,
 					   &node->handle, GFP_KERNEL,
@@ -438,8 +438,8 @@ gk20a_instobj_ctor_iommu(struct gk20a_instmem *imem, u32 npages, u32 align,
 	*_node = &node->base;
 	node->dma_addrs = (void *)(node->pages + npages);
 
-	nvkm_memory_ctor(&gk20a_instobj_func_iommu, &node->base.memory);
-	node->base.memory.ptrs = &gk20a_instobj_ptrs;
+	nvkm_memory_ctor(&gk20a_instobj_func_iommu, &node->base.base.memory);
+	node->base.base.memory.ptrs = &gk20a_instobj_ptrs;
 
 	/* Allocate backing memory */
 	for (i = 0; i < npages; i++) {
@@ -533,7 +533,7 @@ gk20a_instobj_new(struct nvkm_instmem *base, u32 size, u32 align, bool zero,
 	else
 		ret = gk20a_instobj_ctor_dma(imem, size >> PAGE_SHIFT,
 					     align, &node);
-	*pmemory = node ? &node->memory : NULL;
+	*pmemory = node ? &node->base.memory : NULL;
 	if (ret)
 		return ret;