Op 04-09-13 05:41, Ben Skeggs schreef: > On Thu, Aug 22, 2013 at 5:12 PM, Maarten Lankhorst > <maarten.lankhorst@xxxxxxxxxxxxx> wrote: >> Op 22-08-13 02:10, Ilia Mirkin schreef: >>> The code expects non-VRAM mem nodes to have a pages list. If that's not >>> set, it will do a null deref down the line. Warn on that condition and >>> return an error. >>> >>> See https://bugs.freedesktop.org/show_bug.cgi?id=64774 >>> >>> Reported-by: Pasi Kärkkäinen <pasik@xxxxxx> >>> Tested-by: Pasi Kärkkäinen <pasik@xxxxxx> >>> Signed-off-by: Ilia Mirkin <imirkin@xxxxxxxxxxxx> >>> Cc: <stable@xxxxxxxxxxxxxxx> # 3.8+ >>> --- >>> >>> I don't exactly understand what's going on, but this is just a >>> straightforward way to avoid a null deref that you see happens in the >>> bug. I haven't figured out the root cause of this, but it's getting >>> well into the "I have no idea how TTM works" space. However this seems >>> like a bit of defensive programming -- nouveau_vm_map_sg will pass >>> node->pages as a list down, which will be dereferenced by >>> nvc0_vm_map_sg. Perhaps the other arguments should make that >>> dereferencing not happen, but it definitely was happening here, as you >>> can see in the bug. >>> >>> Ben/Maarten, I'll let you judge whether this check is appropriate, >>> since like I hope I was able to convey above, I'm just not really sure :) >> Not it really isn't appropriate.. >> >> You'd have to call call nouveau_vm_map_sg_table instead, the only place that doesn't handle that correctly >> is where it's not expected to be called. >> >> Here, have a completely untested patch to fix things... >> >> diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c >> --- a/drivers/gpu/drm/nouveau/nouveau_display.c >> +++ b/drivers/gpu/drm/nouveau/nouveau_display.c >> @@ -138,17 +143,26 @@ nouveau_user_framebuffer_create(struct drm_device *dev, >> { >> struct nouveau_framebuffer *nouveau_fb; >> struct drm_gem_object *gem; >> + struct nouveau_bo *nvbo; >> int ret = -ENOMEM; >> >> gem = drm_gem_object_lookup(dev, file_priv, mode_cmd->handles[0]); >> if (!gem) >> return ERR_PTR(-ENOENT); >> >> + nvbo = nouveau_gem_object(gem); >> + if (!(nvbo->valid_domains & NOUVEAU_GEM_DOMAIN_VRAM)) { >> + nv_warn(nouveau_drm(dev), "Trying to create a fb in vram with" >> + " valid_domains=%08x\n", nvbo->valid_domains); >> + ret = -EINVAL; >> + goto err_unref; >> + } >> + > Definitely the right idea, we can't handle this case right now. > However, we may someday want/need to be able to scan out of system > memory, so this is the wrong place. > > I suspect the correct thing to do (which'll also handle the > "defensive" part) is to bail in nouveau_bo_move() on attempts to move > a DMA-BUF backed object into VRAM. > > Sound OK? > If it has a WARN_ON or something that would be ok, I didn't find any other places that attempt to move buffers to VRAM though, so it's probably harmless. When looking into this bug I noticed that nouveau_bo_vma_add needs to have a check for nvbo->page_shift == vma->vm->vmm->spg_shift, and only if the check is true it should map the page in TTM_PL_TT. Patch below. Should probably also be cc'd to stable. ~Maarten diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c index 89b992e..355a1b7 100644 --- a/drivers/gpu/drm/nouveau/nouveau_bo.c +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c @@ -1560,7 +1560,8 @@ nouveau_bo_vma_add(struct nouveau_bo *nvbo, struct nouveau_vm *vm, if (nvbo->bo.mem.mem_type == TTM_PL_VRAM) nouveau_vm_map(vma, nvbo->bo.mem.mm_node); - else if (nvbo->bo.mem.mem_type == TTM_PL_TT) { + else if (nvbo->bo.mem.mem_type == TTM_PL_TT && + nvbo->page_shift == vma->vm->vmm->spg_shift) { if (node->sg) nouveau_vm_map_sg_table(vma, 0, size, node); else _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
