[Intel-gfx] i915 "GPU HANG", bisected to a2daa27c0c61 "swiotlb: simplify swiotlb_max_segment"
Christoph Hellwig
hch at lst.de
Tue Oct 18 08:24:13 UTC 2022
On Tue, Oct 18, 2022 at 05:52:16AM +0200, Marek Marczykowski-Górecki wrote:
> not only) when using IGD in Xen PV dom0. After not very long time Xorg
> crashes, and dmesg contain messages like this:
>
> i915 0000:00:02.0: [drm] GPU HANG: ecode 7:1:01fffbfe, in Xorg [5337]
> i915 0000:00:02.0: [drm] Resetting rcs0 for stopped heartbeat on rcs0
> i915 0000:00:02.0: [drm] Xorg[5337] context reset due to GPU hang
<snip>
> I tried reverting just this commit on top of 6.0.x, but the context
> changed significantly in subsequent commits, so after trying reverting
> it together with 3 or 4 more commits I gave up.
>
> What may be an important detail, the system heavily uses cross-VM shared
> memory (gntdev) to map window contents from VMs. This is Qubes OS, and
> it uses Xen 4.14.
Can you try the patch below?
---
>From 26fe4749750f1bf843666ca777e297279994e33a Mon Sep 17 00:00:00 2001
From: Robert Beckett <bob.beckett at collabora.com>
Date: Tue, 26 Jul 2022 16:39:35 +0100
Subject: drm/i915: stop abusing swiotlb_max_segment
Calling swiotlb functions directly is nowadays considered harmful. See
https://lore.kernel.org/intel-gfx/20220711082614.GA29487@lst.de/
Replace swiotlb_max_segment() calls with dma_max_mapping_size().
In i915_gem_object_get_pages_internal() no longer consider max_segment
only if CONFIG_SWIOTLB is enabled. There can be other (iommu related)
causes of specific max segment sizes.
Signed-off-by: Robert Beckett <bob.beckett at collabora.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
[hch: added the Xen hack]
---
drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 +++----------
drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 2 +-
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 4 +--
drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 2 +-
drivers/gpu/drm/i915/i915_scatterlist.h | 30 +++++++++++---------
5 files changed, 25 insertions(+), 32 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
index c698f95af15fe..629acb403a2c9 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
@@ -6,7 +6,6 @@
#include <linux/scatterlist.h>
#include <linux/slab.h>
-#include <linux/swiotlb.h>
#include "i915_drv.h"
#include "i915_gem.h"
@@ -38,22 +37,12 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
struct scatterlist *sg;
unsigned int sg_page_sizes;
unsigned int npages;
- int max_order;
+ int max_order = MAX_ORDER;
+ unsigned int max_segment;
gfp_t gfp;
- max_order = MAX_ORDER;
-#ifdef CONFIG_SWIOTLB
- if (is_swiotlb_active(obj->base.dev->dev)) {
- unsigned int max_segment;
-
- max_segment = swiotlb_max_segment();
- if (max_segment) {
- max_segment = max_t(unsigned int, max_segment,
- PAGE_SIZE) >> PAGE_SHIFT;
- max_order = min(max_order, ilog2(max_segment));
- }
- }
-#endif
+ max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT;
+ max_order = min(max_order, get_order(max_segment));
gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
if (IS_I965GM(i915) || IS_I965G(i915)) {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index f42ca1179f373..11125c32dd35d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -194,7 +194,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
struct intel_memory_region *mem = obj->mm.region;
struct address_space *mapping = obj->base.filp->f_mapping;
const unsigned long page_count = obj->base.size / PAGE_SIZE;
- unsigned int max_segment = i915_sg_segment_size();
+ unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
struct sg_table *st;
struct sgt_iter sgt_iter;
struct page *page;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index e3fc38dd5db04..de5d0a7241027 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- const unsigned int max_segment = i915_sg_segment_size();
+ const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
struct file *filp = i915_tt->filp;
struct sgt_iter sgt_iter;
@@ -538,7 +538,7 @@ static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
ret = sg_alloc_table_from_pages_segment(st,
ttm->pages, ttm->num_pages,
0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
- i915_sg_segment_size(), GFP_KERNEL);
+ i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
if (ret) {
st->sgl = NULL;
return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 8423df021b713..e4515d6acd43c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -129,7 +129,7 @@ static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
{
const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
- unsigned int max_segment = i915_sg_segment_size();
+ unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev);
struct sg_table *st;
unsigned int sg_page_sizes;
struct page **pvec;
diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
index 9ddb3e743a3e5..c278888f71528 100644
--- a/drivers/gpu/drm/i915/i915_scatterlist.h
+++ b/drivers/gpu/drm/i915/i915_scatterlist.h
@@ -9,7 +9,8 @@
#include <linux/pfn.h>
#include <linux/scatterlist.h>
-#include <linux/swiotlb.h>
+#include <linux/dma-mapping.h>
+#include <xen/xen.h>
#include "i915_gem.h"
@@ -127,19 +128,22 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg)
return page_sizes;
}
-static inline unsigned int i915_sg_segment_size(void)
+static inline unsigned int i915_sg_segment_size(struct device *dev)
{
- unsigned int size = swiotlb_max_segment();
-
- if (size == 0)
- size = UINT_MAX;
-
- size = rounddown(size, PAGE_SIZE);
- /* swiotlb_max_segment_size can return 1 byte when it means one page. */
- if (size < PAGE_SIZE)
- size = PAGE_SIZE;
-
- return size;
+ size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));
+
+ /*
+ * Xen on x86 can reshuffle pages under us. The DMA API takes
+ * care of that both in dma_alloc_* (by calling into the hypervisor
+ * to make the pages contigous) and in dma_map_* (by bounce buffering).
+ * But i915 abuses ignores the coherency aspects of the DMA API and
+ * thus can't cope with bounce buffering actually happening, so add
+ * a hack here to force small allocations and mapping when running on
+ * Xen. (good luck with TDX, btw --hch)
+ */
+ if (IS_ENABLED(CONFIG_X86) && xen_domain())
+ max = PAGE_SIZE;
+ return round_down(max, PAGE_SIZE);
}
bool i915_sg_trim(struct sg_table *orig_st);
--
2.30.2
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