Regression introduced by 90797e6d1ec0dfde6ba62a48b9ee3803887d6ed4 ("drm/i915: create compact dma scatter lists for gem objects") Was:Re: i915 mapping large (3MB) scatter list, hitting limits on certain IOMMUs that can only map contingous regions up to 2MB.

On Fri, Jun 21, 2013 at 03:28:28PM -0400, Konrad Rzeszutek Wilk wrote:

Hey,

CC-ing Imre,

Imre, your patch 90797e6d1ec0dfde6ba62a48b9ee3803887d6ed4 ("drm/i915: create compact dma scatter lists for gem objects") is the cause of the regression.

If I revert your patch it boots fine without any trouble.

I am not entirely sure why that is - as I added some debug code in lib/swiotlb.c to trigger when it can't find 3MB area (which is what I thought initially was the issue) - but none of the debug code seems to be hit.

Any thoughts?

I am using an ThinkPad X230 with an Intel HD 4000. With a stock Fedora 18 (3.9.6) I can get it to boot and work just fine with Xen. If I use v3.10-rc6 I found that i915 would halt with a

[drm:intel_pipe_set_base] *ERROR* pin & fence failed [drm:intel_crtc_set_config] *ERROR* failed to set mode on [CRTC:3], err = -28

after a bit of debugging (see patch below) I traced it down to the fact that the scatter list that is provided at the end has a huge (3MB) page. I am wondering if anybody knows what patch might have introduced it to grab such a large memory segment?

The other thing I am wondering is if there are some fallbacks when the underlaying IOMMU can't deal with a request for contingous regions that are more than 2MB?

Thanks.

...

From a681a4adb4738c32cb1acdf6f5161bf877816b01 Mon Sep 17 00:00:00 2001

From: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Date: Fri, 21 Jun 2013 11:17:55 -0400 Subject: [PATCH] dbug: print scatterlist.

------------[ cut here ]------------ WARNING: at drivers/gpu/drm/i915/i915_gem_gtt.c:418 i915_gem_gtt_prepare_object+0x180/0x200() 10 but got 0 Modules linked in: crc32_pclmul sdhci_pci crc32c_intel sdhci mmc_core ghash_clmulni_intel CPU: 0 PID: 216 Comm: plymouthd Not tainted 3.10.0-rc6+ #16 Hardware name: LENOVO 2325DV4/2325DV4, BIOS G2ET86WW (2.06 ) 11/13/2012 0000000000000009 ffff8801fa42d958 ffffffff816e6d89 ffff8801fa42d998 ffffffff8105d2b0 ffff8801fa42d988 0000000000000000 ffff8801fb0f4d80 ffffffff81c172e0 ffff8801fa76f000 000000000000000a ffff8801fa42d9f8 Call Trace: [<ffffffff816e6d89>] dump_stack+0x19/0x1b [<ffffffff8105d2b0>] warn_slowpath_common+0x70/0xa0 [<ffffffff8105d396>] warn_slowpath_fmt+0x46/0x50 [<ffffffff8142a740>] i915_gem_gtt_prepare_object+0x180/0x200 [<ffffffff81423581>] i915_gem_object_pin+0x321/0x670 [<ffffffff81423951>] i915_gem_object_pin_to_display_plane+0x81/0x190 [<ffffffff814381b5>] intel_pin_and_fence_fb_obj+0x85/0x1a0 [<ffffffff8143999c>] intel_pipe_set_base+0x7c/0x220 [<ffffffff814409be>] intel_crtc_set_config+0x89e/0x990 [<ffffffff813ffdae>] drm_mode_set_config_internal+0x2e/0x60 [<ffffffff814023ab>] drm_mode_setcrtc+0xfb/0x620 [<ffffffff811850f9>] ? kmem_cache_alloc_trace+0x39/0x1f0 [<ffffffff813f9767>] ? drm_vm_open_locked+0x57/0x90 [<ffffffff813f2e39>] drm_ioctl+0x549/0x680 [<ffffffff814022b0>] ? drm_mode_setplane+0x3b0/0x3b0 [<ffffffff811aef77>] do_vfs_ioctl+0x97/0x580 [<ffffffff81295dca>] ? inode_has_perm.isra.32.constprop.62+0x2a/0x30 [<ffffffff81297397>] ? file_has_perm+0x97/0xb0 [<ffffffff811af4f1>] SyS_ioctl+0x91/0xb0 [<ffffffff816f63e7>] tracesys+0xdd/0xe2 ---[ end trace 7b6adc5450d9a9e1 ]--- i915 0000:00:02.0: i915_gem_gtt_prepare_object: Mapping 10 pages, mapped: 0 [0] virT:ffff8801fd37c000 dma: 1fd37c000, size:4096 [1] virT:ffff8801fd37b000 dma: 1fd37b000, size:4096 [2] virT:ffff8801fd37a000 dma: 1fd37a000, size:4096 [3] virT:ffff8801fd378000 dma: 1fd378000, size:4096 [4] virT:ffff8801fd131000 dma: 1fd131000, size:4096 [5] virT:ffff880200c36000 dma: 200c36000, size:4096 [6] virT:ffff8801fd1a4000 dma: 1fd1a4000, size:69632 [7] virT:ffff8801fd3bb000 dma: 1fd3bb000, size:4096 [8] virT:ffff8801fd3c0000 dma: 1fd3c0000, size:262144 [9] virT:ffff8801f9400000 dma: 1f9400000, size:3866624 [drm] 3011: ret:-28 [drm] 3540: ret:-28 [drm] 3364: ret:-28 [drm:intel_pin_and_fence_fb_obj] *ERROR* i915_gem_object_pin_to_display_plane failed: -28 [drm:intel_pipe_set_base] *ERROR* pin & fence failed [drm:intel_crtc_set_config] *ERROR* failed to set mode on [CRTC:3], err = -28

Signed-off-by: Konrad Rzeszutek Wilk konrad.wilk@oracle.com

drivers/gpu/drm/i915/i915_drv.c | 6 ++++++ drivers/gpu/drm/i915/i915_gem_gtt.c | 28 +++++++++++++++++++++++++--- 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c index 8411942..141c6fb 100644 --- a/drivers/gpu/drm/i915/i915_drv.c +++ b/drivers/gpu/drm/i915/i915_drv.c @@ -133,6 +133,12 @@ module_param_named(coherent, use_coherent, int, 0600); MODULE_PARM_DESC(use_coherent, "Use coherent DMA API calls (default: false)");

+int i915_sgl __read_mostly = 0; +module_param_named(sgl, i915_sgl, int, 0600); +MODULE_PARM_DESC(sgl,

•  "Print scatterlist SG's when DMA mapping them (default: false)");
  

static struct drm_driver driver; extern int intel_agp_enabled;

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index acb3b3f..292179c 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -28,6 +28,7 @@ #include "i915_trace.h" #include "intel_drv.h"

+extern int use_coherent; typedef uint32_t gen6_gtt_pte_t;

/* PPGTT stuff */ @@ -403,15 +404,36 @@ void i915_gem_restore_gtt_mappings(struct drm_device *dev)

i915_gem_chipset_flush(dev); }

+extern int i915_sgl; int i915_gem_gtt_prepare_object(struct drm_i915_gem_object *obj) {

• int elem; if (obj->has_dma_mapping) return 0;

• if (!dma_map_sg(&obj->base.dev->pdev->dev,

• elem = dma_map_sg(&obj->base.dev->pdev->dev, obj->pages->sgl, obj->pages->nents,

• 	PCI_DMA_BIDIRECTIONAL))
  

• 	PCI_DMA_BIDIRECTIONAL);
  

• WARN(elem == 0, "%d but got %d", obj->pages->nents, elem);

• if (i915_sgl && obj->pages && obj->pages->sgl) {

• int i;
  

• struct scatterlist *s;
  

• if (obj->base.dev) {
  

• 	dev_info(&obj->base.dev->pdev->dev, "%s: Mapping %d pages, mapped: %d\n",
  

• 	 	__func__,obj->pages->nents, elem);
  

• } else
  

• 	printk(KERN_INFO "%s: no dev, %d pages, mapped: %d\n",__func__,
  

• 		obj->pages->nents, elem);
  

• for_each_sg(obj->pages->sgl, s, obj->pages->nents, i) {
  

• 	printk(KERN_INFO "[%d] virT:%lx dma: %lx, size:%d\n", i,
  

• 		(unsigned long)sg_virt(s), (unsigned long)sg_phys(s), s->length);
  

• }
  

• }

• if (!elem) return -ENOSPC;

  return 0;

-- 1.8.1.4

---

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