On Wed, Aug 14, 2019 at 07:58:27AM +0200, Gerd Hoffmann wrote:
> > Hi Gerd,
> > 
> > I've been seeing a regression on Nouveau with recent linux-next releases
> > and git bisect points at this commit as the first bad one. If I revert
> > it (there's a tiny conflict with a patch that was merged subsequently),
> > things are back to normal.
> > 
> > I think the reason for this issue is that Nouveau doesn't use GEM
> > objects for all buffer objects,
> 
> That shouldn't be a problem ...
> 
> > and even when it uses GEM objects, the
> > code will not initialize the GEM object until after the buffer objects
> > and the backing TTM objects have been created.
> 
> ... but the initialization order is.
> 
> ttm_bo_uses_embedded_gem_object() assumes gem gets initialized first.
> 
> drm_gem_object_init() init calling drm_vma_node_reset() again is
> probably the root cause for the breakage.
> 
> > I tried to fix that by making sure drm_gem_object_init() gets called by
> > Nouveau before ttm_bo_init(), but the changes are fairly involved and I
> > was unable to get the GEM reference counting right. I can look into the
> > proper fix some more, but it might be worth reverting this patch for
> > now to get Nouveau working again.
> 
> Changing the order doesn't look hard.  Patch attached (untested, have no
> test hardware).  But maybe I missed some detail ...
> 
> The other patch attached works around the issue with a flag, to avoid
> drm_vma_node_reset() being called twice.

I came up with something very similar by splitting up nouveau_bo_new()
into allocation and initialization steps, so that when necessary the GEM
object can be initialized in between. I think that's slightly more
flexible and easier to understand than a boolean flag.

Thierry
From a1130a6affcb7c00133e89f3e498cb6757f5bb51 Mon Sep 17 00:00:00 2001
From: Thierry Reding <tred...@nvidia.com>
Date: Wed, 14 Aug 2019 11:00:48 +0200
Subject: [PATCH] drm/nouveau: Initialize GEM object before TTM object

TTM assumes that drivers initialize the embedded GEM object before
calling the ttm_bo_init() function. This is not currently the case
in the Nouveau driver. Fix this by splitting up nouveau_bo_new()
into nouveau_bo_alloc() and nouveau_bo_init() so that the GEM can
be initialized before TTM BO initialization when necessary.

Fixes: b96f3e7c8069 ("drm/ttm: use gem vma_node")
Signed-off-by: Thierry Reding <tred...@nvidia.com>
---
 drivers/gpu/drm/nouveau/nouveau_bo.c    | 69 ++++++++++++++++---------
 drivers/gpu/drm/nouveau/nouveau_bo.h    |  4 ++
 drivers/gpu/drm/nouveau/nouveau_gem.c   | 29 ++++++-----
 drivers/gpu/drm/nouveau/nouveau_prime.c | 16 ++++--
 4 files changed, 77 insertions(+), 41 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c 
b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 99e391be9370..b3d3e07de1af 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -185,31 +185,24 @@ nouveau_bo_fixup_align(struct nouveau_bo *nvbo, u32 flags,
        *size = roundup_64(*size, PAGE_SIZE);
 }
 
-int
-nouveau_bo_new(struct nouveau_cli *cli, u64 size, int align,
-              uint32_t flags, uint32_t tile_mode, uint32_t tile_flags,
-              struct sg_table *sg, struct reservation_object *robj,
-              struct nouveau_bo **pnvbo)
+struct nouveau_bo *
+nouveau_bo_alloc(struct nouveau_cli *cli, u64 size, u32 flags, u32 tile_mode,
+                u32 tile_flags)
 {
        struct nouveau_drm *drm = cli->drm;
        struct nouveau_bo *nvbo;
        struct nvif_mmu *mmu = &cli->mmu;
        struct nvif_vmm *vmm = cli->svm.cli ? &cli->svm.vmm : &cli->vmm.vmm;
-       size_t acc_size;
-       int type = ttm_bo_type_device;
-       int ret, i, pi = -1;
+       int i, pi = -1;
 
        if (!size) {
                NV_WARN(drm, "skipped size %016llx\n", size);
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
        }
 
-       if (sg)
-               type = ttm_bo_type_sg;
-
        nvbo = kzalloc(sizeof(struct nouveau_bo), GFP_KERNEL);
        if (!nvbo)
-               return -ENOMEM;
+               return ERR_PTR(-ENOMEM);
        INIT_LIST_HEAD(&nvbo->head);
        INIT_LIST_HEAD(&nvbo->entry);
        INIT_LIST_HEAD(&nvbo->vma_list);
@@ -231,7 +224,7 @@ nouveau_bo_new(struct nouveau_cli *cli, u64 size, int align,
                nvbo->kind = (tile_flags & 0x0000ff00) >> 8;
                if (!nvif_mmu_kind_valid(mmu, nvbo->kind)) {
                        kfree(nvbo);
-                       return -EINVAL;
+                       return ERR_PTR(-EINVAL);
                }
 
                nvbo->comp = mmu->kind[nvbo->kind] != nvbo->kind;
@@ -241,7 +234,7 @@ nouveau_bo_new(struct nouveau_cli *cli, u64 size, int align,
                nvbo->comp = (tile_flags & 0x00030000) >> 16;
                if (!nvif_mmu_kind_valid(mmu, nvbo->kind)) {
                        kfree(nvbo);
-                       return -EINVAL;
+                       return ERR_PTR(-EINVAL);
                }
        } else {
                nvbo->zeta = (tile_flags & 0x00000007);
@@ -278,7 +271,7 @@ nouveau_bo_new(struct nouveau_cli *cli, u64 size, int align,
        }
 
        if (WARN_ON(pi < 0))
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
 
        /* Disable compression if suitable settings couldn't be found. */
        if (nvbo->comp && !vmm->page[pi].comp) {
@@ -288,23 +281,51 @@ nouveau_bo_new(struct nouveau_cli *cli, u64 size, int 
align,
        }
        nvbo->page = vmm->page[pi].shift;
 
+       return nvbo;
+}
+
+int
+nouveau_bo_init(struct nouveau_bo *nvbo, u64 size, int align, u32 flags,
+               struct sg_table *sg, struct reservation_object *robj)
+{
+       int type = sg ? ttm_bo_type_sg : ttm_bo_type_device;
+       size_t acc_size;
+       int ret;
+
+       acc_size = ttm_bo_dma_acc_size(nvbo->bo.bdev, size, sizeof(*nvbo));
+
        nouveau_bo_fixup_align(nvbo, flags, &align, &size);
        nvbo->bo.mem.num_pages = size >> PAGE_SHIFT;
        nouveau_bo_placement_set(nvbo, flags, 0);
 
-       acc_size = ttm_bo_dma_acc_size(&drm->ttm.bdev, size,
-                                      sizeof(struct nouveau_bo));
-
-       ret = ttm_bo_init(&drm->ttm.bdev, &nvbo->bo, size,
-                         type, &nvbo->placement,
-                         align >> PAGE_SHIFT, false, acc_size, sg,
-                         robj, nouveau_bo_del_ttm);
-
+       ret = ttm_bo_init(nvbo->bo.bdev, &nvbo->bo, size, type,
+                         &nvbo->placement, align >> PAGE_SHIFT, false,
+                         acc_size, sg, robj, nouveau_bo_del_ttm);
        if (ret) {
                /* ttm will call nouveau_bo_del_ttm if it fails.. */
                return ret;
        }
 
+       return 0;
+}
+
+int
+nouveau_bo_new(struct nouveau_cli *cli, u64 size, int align,
+              uint32_t flags, uint32_t tile_mode, uint32_t tile_flags,
+              struct sg_table *sg, struct reservation_object *robj,
+              struct nouveau_bo **pnvbo)
+{
+       struct nouveau_bo *nvbo;
+       int ret;
+
+       nvbo = nouveau_bo_alloc(cli, size, flags, tile_mode, tile_flags);
+       if (IS_ERR(nvbo))
+               return PTR_ERR(nvbo);
+
+       ret = nouveau_bo_init(nvbo, size, align, flags, sg, robj);
+       if (ret)
+               return ret;
+
        *pnvbo = nvbo;
        return 0;
 }
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.h 
b/drivers/gpu/drm/nouveau/nouveau_bo.h
index d675efe8e7f9..7529035b971f 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.h
@@ -71,6 +71,10 @@ nouveau_bo_ref(struct nouveau_bo *ref, struct nouveau_bo 
**pnvbo)
 extern struct ttm_bo_driver nouveau_bo_driver;
 
 void nouveau_bo_move_init(struct nouveau_drm *);
+struct nouveau_bo *nouveau_bo_alloc(struct nouveau_cli *, u64 size, u32 flags,
+                                   u32 tile_mode, u32 tile_flags);
+int  nouveau_bo_init(struct nouveau_bo *, u64 size, int align, u32 flags,
+                    struct sg_table *sg, struct reservation_object *robj);
 int  nouveau_bo_new(struct nouveau_cli *, u64 size, int align, u32 flags,
                    u32 tile_mode, u32 tile_flags, struct sg_table *sg,
                    struct reservation_object *robj,
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c 
b/drivers/gpu/drm/nouveau/nouveau_gem.c
index c7368aa0bdec..e9c772e07789 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -188,11 +188,23 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int 
align, uint32_t domain,
        if (domain & NOUVEAU_GEM_DOMAIN_COHERENT)
                flags |= TTM_PL_FLAG_UNCACHED;
 
-       ret = nouveau_bo_new(cli, size, align, flags, tile_mode,
-                            tile_flags, NULL, NULL, pnvbo);
-       if (ret)
+       nvbo = nouveau_bo_alloc(cli, size, flags, tile_mode, tile_flags);
+       if (IS_ERR(nvbo))
+               return PTR_ERR(nvbo);
+
+       /* Initialize the embedded gem-object. We return a single gem-reference
+        * to the caller, instead of a normal nouveau_bo ttm reference. */
+       ret = drm_gem_object_init(drm->dev, &nvbo->bo.base, size);
+       if (ret) {
+               nouveau_bo_ref(NULL, &nvbo);
+               return ret;
+       }
+
+       ret = nouveau_bo_init(nvbo, size, align, flags, NULL, NULL);
+       if (ret) {
+               nouveau_bo_ref(NULL, &nvbo);
                return ret;
-       nvbo = *pnvbo;
+       }
 
        /* we restrict allowed domains on nv50+ to only the types
         * that were requested at creation time.  not possibly on
@@ -203,15 +215,8 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int 
align, uint32_t domain,
        if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_TESLA)
                nvbo->valid_domains &= domain;
 
-       /* Initialize the embedded gem-object. We return a single gem-reference
-        * to the caller, instead of a normal nouveau_bo ttm reference. */
-       ret = drm_gem_object_init(drm->dev, &nvbo->bo.base, nvbo->bo.mem.size);
-       if (ret) {
-               nouveau_bo_ref(NULL, pnvbo);
-               return -ENOMEM;
-       }
-
        nvbo->bo.persistent_swap_storage = nvbo->bo.base.filp;
+       *pnvbo = nvbo;
        return 0;
 }
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c 
b/drivers/gpu/drm/nouveau/nouveau_prime.c
index e86ad7ae622b..0ca71a84e23a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_prime.c
+++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
@@ -63,28 +63,34 @@ struct drm_gem_object 
*nouveau_gem_prime_import_sg_table(struct drm_device *dev,
        struct nouveau_drm *drm = nouveau_drm(dev);
        struct nouveau_bo *nvbo;
        struct reservation_object *robj = attach->dmabuf->resv;
+       size_t size = attach->dmabuf->size;
        u32 flags = 0;
        int ret;
 
        flags = TTM_PL_FLAG_TT;
 
        reservation_object_lock(robj, NULL);
-       ret = nouveau_bo_new(&drm->client, attach->dmabuf->size, 0, flags, 0, 0,
-                            sg, robj, &nvbo);
+       nvbo = nouveau_bo_alloc(&drm->client, size, flags, 0, 0);
        reservation_object_unlock(robj);
-       if (ret)
-               return ERR_PTR(ret);
+       if (IS_ERR(nvbo))
+               return ERR_CAST(nvbo);
 
        nvbo->valid_domains = NOUVEAU_GEM_DOMAIN_GART;
 
        /* Initialize the embedded gem-object. We return a single gem-reference
         * to the caller, instead of a normal nouveau_bo ttm reference. */
-       ret = drm_gem_object_init(dev, &nvbo->bo.base, nvbo->bo.mem.size);
+       ret = drm_gem_object_init(dev, &nvbo->bo.base, size);
        if (ret) {
                nouveau_bo_ref(NULL, &nvbo);
                return ERR_PTR(-ENOMEM);
        }
 
+       ret = nouveau_bo_init(nvbo, size, 0, flags, sg, robj);
+       if (ret) {
+               nouveau_bo_ref(NULL, &nvbo);
+               return ERR_PTR(ret);
+       }
+
        return &nvbo->bo.base;
 }
 
-- 
2.22.0

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