drm/nouveau/svm: map pages after migration

When memory is migrated to the GPU, it is likely to be accessed by GPU
code soon afterwards. Instead of waiting for a GPU fault, map the
migrated memory into the GPU page tables with the same access permissions
as the source CPU page table entries. This preserves copy on write
semantics.
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_dmem.c

@@ -25,12 +25,14 @@
 #include "nouveau_dma.h"
 #include "nouveau_mem.h"
 #include "nouveau_bo.h"
+#include "nouveau_svm.h"
 
 #include <nvif/class.h>
 #include <nvif/object.h>
 #include <nvif/if000c.h>
 #include <nvif/if500b.h>
 #include <nvif/if900b.h>
+#include <nvif/if000c.h>
 
 #include <linux/sched/mm.h>
 #include <linux/hmm.h>
@@ -561,10 +563,11 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 }
 
 static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
-		unsigned long src, dma_addr_t *dma_addr)
+		unsigned long src, dma_addr_t *dma_addr, u64 *pfn)
 {
 	struct device *dev = drm->dev->dev;
 	struct page *dpage, *spage;
+	unsigned long paddr;
 
 	spage = migrate_pfn_to_page(src);
 	if (!spage || !(src & MIGRATE_PFN_MIGRATE))
@@ -572,17 +575,21 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
 
 	dpage = nouveau_dmem_page_alloc_locked(drm);
 	if (!dpage)
-		return 0;
+		goto out;
 
 	*dma_addr = dma_map_page(dev, spage, 0, PAGE_SIZE, DMA_BIDIRECTIONAL);
 	if (dma_mapping_error(dev, *dma_addr))
 		goto out_free_page;
 
+	paddr = nouveau_dmem_page_addr(dpage);
 	if (drm->dmem->migrate.copy_func(drm, 1, NOUVEAU_APER_VRAM,
-			nouveau_dmem_page_addr(dpage), NOUVEAU_APER_HOST,
-			*dma_addr))
+			paddr, NOUVEAU_APER_HOST, *dma_addr))
 		goto out_dma_unmap;
 
+	*pfn = NVIF_VMM_PFNMAP_V0_V | NVIF_VMM_PFNMAP_V0_VRAM |
+		((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
+	if (src & MIGRATE_PFN_WRITE)
+		*pfn |= NVIF_VMM_PFNMAP_V0_W;
 	return migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
 
 out_dma_unmap:
@@ -590,18 +597,20 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
 out_free_page:
 	nouveau_dmem_page_free_locked(drm, dpage);
 out:
+	*pfn = NVIF_VMM_PFNMAP_V0_NONE;
 	return 0;
 }
 
 static void nouveau_dmem_migrate_chunk(struct nouveau_drm *drm,
-		struct migrate_vma *args, dma_addr_t *dma_addrs)
+		struct nouveau_svmm *svmm, struct migrate_vma *args,
+		dma_addr_t *dma_addrs, u64 *pfns)
 {
 	struct nouveau_fence *fence;
 	unsigned long addr = args->start, nr_dma = 0, i;
 
 	for (i = 0; addr < args->end; i++) {
 		args->dst[i] = nouveau_dmem_migrate_copy_one(drm, args->src[i],
-				dma_addrs + nr_dma);
+				dma_addrs + nr_dma, pfns + i);
 		if (args->dst[i])
 			nr_dma++;
 		addr += PAGE_SIZE;
@@ -610,20 +619,18 @@ static void nouveau_dmem_migrate_chunk(struct nouveau_drm *drm,
 	nouveau_fence_new(drm->dmem->migrate.chan, false, &fence);
 	migrate_vma_pages(args);
 	nouveau_dmem_fence_done(&fence);
+	nouveau_pfns_map(svmm, args->vma->vm_mm, args->start, pfns, i);
 
 	while (nr_dma--) {
 		dma_unmap_page(drm->dev->dev, dma_addrs[nr_dma], PAGE_SIZE,
 				DMA_BIDIRECTIONAL);
 	}
-	/*
-	 * FIXME optimization: update GPU page table to point to newly migrated
-	 * memory.
-	 */
 	migrate_vma_finalize(args);
 }
 
 int
 nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
+			 struct nouveau_svmm *svmm,
 			 struct vm_area_struct *vma,
 			 unsigned long start,
 			 unsigned long end)
@@ -635,7 +642,8 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 		.vma		= vma,
 		.start		= start,
 	};
-	unsigned long c, i;
+	unsigned long i;
+	u64 *pfns;
 	int ret = -ENOMEM;
 
 	args.src = kcalloc(max, sizeof(*args.src), GFP_KERNEL);
@@ -649,19 +657,25 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 	if (!dma_addrs)
 		goto out_free_dst;
 
-	for (i = 0; i < npages; i += c) {
-		c = min(SG_MAX_SINGLE_ALLOC, npages);
-		args.end = start + (c << PAGE_SHIFT);
+	pfns = nouveau_pfns_alloc(max);
+	if (!pfns)
+		goto out_free_dma;
+
+	for (i = 0; i < npages; i += max) {
+		args.end = start + (max << PAGE_SHIFT);
 		ret = migrate_vma_setup(&args);
 		if (ret)
-			goto out_free_dma;
+			goto out_free_pfns;
 
 		if (args.cpages)
-			nouveau_dmem_migrate_chunk(drm, &args, dma_addrs);
+			nouveau_dmem_migrate_chunk(drm, svmm, &args, dma_addrs,
+						   pfns);
 		args.start = args.end;
 	}
 
 	ret = 0;
+out_free_pfns:
+	nouveau_pfns_free(pfns);
 out_free_dma:
 	kfree(dma_addrs);
 out_free_dst:

drivers/gpu/drm/nouveau/nouveau_dmem.h

@@ -25,6 +25,7 @@
 struct drm_device;
 struct drm_file;
 struct nouveau_drm;
+struct nouveau_svmm;
 struct hmm_range;
 
 #if IS_ENABLED(CONFIG_DRM_NOUVEAU_SVM)
@@ -34,6 +35,7 @@ void nouveau_dmem_suspend(struct nouveau_drm *);
 void nouveau_dmem_resume(struct nouveau_drm *);
 
 int nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
+			     struct nouveau_svmm *svmm,
 			     struct vm_area_struct *vma,
 			     unsigned long start,
 			     unsigned long end);

drivers/gpu/drm/nouveau/nouveau_svm.c

@@ -70,6 +70,12 @@ struct nouveau_svm {
 #define SVM_DBG(s,f,a...) NV_DEBUG((s)->drm, "svm: "f"\n", ##a)
 #define SVM_ERR(s,f,a...) NV_WARN((s)->drm, "svm: "f"\n", ##a)
 
+struct nouveau_pfnmap_args {
+	struct nvif_ioctl_v0 i;
+	struct nvif_ioctl_mthd_v0 m;
+	struct nvif_vmm_pfnmap_v0 p;
+};
+
 struct nouveau_ivmm {
 	struct nouveau_svmm *svmm;
 	u64 inst;
@@ -187,7 +193,8 @@ nouveau_svmm_bind(struct drm_device *dev, void *data,
 		addr = max(addr, vma->vm_start);
 		next = min(vma->vm_end, end);
 		/* This is a best effort so we ignore errors */
-		nouveau_dmem_migrate_vma(cli->drm, vma, addr, next);
+		nouveau_dmem_migrate_vma(cli->drm, cli->svm.svmm, vma, addr,
+					 next);
 		addr = next;
 	}
 
@@ -784,6 +791,56 @@ nouveau_svm_fault(struct nvif_notify *notify)
 	return NVIF_NOTIFY_KEEP;
 }
 
+static struct nouveau_pfnmap_args *
+nouveau_pfns_to_args(void *pfns)
+{
+	return container_of(pfns, struct nouveau_pfnmap_args, p.phys);
+}
+
+u64 *
+nouveau_pfns_alloc(unsigned long npages)
+{
+	struct nouveau_pfnmap_args *args;
+
+	args = kzalloc(struct_size(args, p.phys, npages), GFP_KERNEL);
+	if (!args)
+		return NULL;
+
+	args->i.type = NVIF_IOCTL_V0_MTHD;
+	args->m.method = NVIF_VMM_V0_PFNMAP;
+	args->p.page = PAGE_SHIFT;
+
+	return args->p.phys;
+}
+
+void
+nouveau_pfns_free(u64 *pfns)
+{
+	struct nouveau_pfnmap_args *args = nouveau_pfns_to_args(pfns);
+
+	kfree(args);
+}
+
+void
+nouveau_pfns_map(struct nouveau_svmm *svmm, struct mm_struct *mm,
+		 unsigned long addr, u64 *pfns, unsigned long npages)
+{
+	struct nouveau_pfnmap_args *args = nouveau_pfns_to_args(pfns);
+	int ret;
+
+	args->p.addr = addr;
+	args->p.size = npages << PAGE_SHIFT;
+
+	mutex_lock(&svmm->mutex);
+
+	svmm->vmm->vmm.object.client->super = true;
+	ret = nvif_object_ioctl(&svmm->vmm->vmm.object, args, sizeof(*args) +
+				npages * sizeof(args->p.phys[0]), NULL);
+	svmm->vmm->vmm.object.client->super = false;
+
+	mutex_unlock(&svmm->mutex);
+}
+
 static void
 nouveau_svm_fault_buffer_fini(struct nouveau_svm *svm, int id)
 {

drivers/gpu/drm/nouveau/nouveau_svm.h

@@ -18,6 +18,11 @@ void nouveau_svmm_fini(struct nouveau_svmm **);
 int nouveau_svmm_join(struct nouveau_svmm *, u64 inst);
 void nouveau_svmm_part(struct nouveau_svmm *, u64 inst);
 int nouveau_svmm_bind(struct drm_device *, void *, struct drm_file *);
+
+u64 *nouveau_pfns_alloc(unsigned long npages);
+void nouveau_pfns_free(u64 *pfns);
+void nouveau_pfns_map(struct nouveau_svmm *svmm, struct mm_struct *mm,
+		      unsigned long addr, u64 *pfns, unsigned long npages);
 #else /* IS_ENABLED(CONFIG_DRM_NOUVEAU_SVM) */
 static inline void nouveau_svm_init(struct nouveau_drm *drm) {}
 static inline void nouveau_svm_fini(struct nouveau_drm *drm) {}