[Intel-gfx] [PATCH] drm/i915: Fix a bug calling sleep function in atomic context

[Bruce Chang]

below is the call trace when this issue is hit

<3> [113.316247] BUG: sleeping function called from invalid context at mm/page_alloc.c:4653
<3> [113.318190] in_atomic(): 1, irqs_disabled(): 0, pid: 678, name: debugfs_test
<4> [113.319900] no locks held by debugfs_test/678.
<3> [113.321002] Preemption disabled at:
<4> [113.321130] [<ffffffffa02506d4>] i915_error_object_create+0x494/0x610 [i915]
<4> [113.327259] Call Trace:
<4> [113.327871] dump_stack+0x67/0x9b
<4> [113.328683] ___might_sleep+0x167/0x250
<4> [113.329618] __alloc_pages_nodemask+0x26b/0x1110
<4> [113.330731] ? ___slab_alloc.constprop.34+0x21c/0x380
<4> [113.331943] ? ___slab_alloc.constprop.34+0x21c/0x380
<4> [113.333169] ? __slab_alloc.isra.28.constprop.33+0x4d/0x70
<4> [113.334614] pool_alloc.constprop.19+0x14/0x60 [i915]
<4> [113.335951] compress_page+0x7c/0x100 [i915]
<4> [113.337110] i915_error_object_create+0x4bd/0x610 [i915]
<4> [113.338515] i915_capture_gpu_state+0x384/0x1680 [i915]
<4> [113.339771] ? __lock_acquire+0x4ac/0x1e90
<4> [113.340785] ? _raw_spin_lock_irqsave_nested+0x1/0x50
<4> [113.342127] i915_gpu_info_open+0x44/0x70 [i915]
<4> [113.343243] full_proxy_open+0x139/0x1b0
<4> [113.344196] ? open_proxy_open+0xc0/0xc0
<4> [113.345149] do_dentry_open+0x1ce/0x3a0
<4> [113.346084] path_openat+0x4c9/0xac0
<4> [113.346967] do_filp_open+0x96/0x110
<4> [113.347848] ? __alloc_fd+0xe0/0x1f0
<4> [113.348736] ? do_sys_open+0x1b8/0x250
<4> [113.349647] do_sys_open+0x1b8/0x250
<4> [113.350526] do_syscall_64+0x55/0x1c0
<4> [113.351418] entry_SYSCALL_64_after_hwframe+0x49/0xbe

After the io_mapping_map_atomic_wc/kmap_atomic, the kernel enters atomic context
but after that, compress_page calls pool_alloc with GFP_KERNEL flag which can
potentially go to sleep.

In order to fix this issue, we either
	1) not enter into atomic context, i.e., to use non atomic version of
		functions like io_mapping_map_wc/kmap,
or
	2) make compress_page run in atomic context.

To follow current design not to run compression in atomic context, so,
use 1) above in this patch.

Signed-off-by: Bruce Chang <yu.bruce.chang at intel.com>
Reviewed-by: Brian Welty <brian.welty at intel.com>
Fixes: 895d8ebeaa924 ("drm/i915: error capture with no ggtt slot")
---
 drivers/gpu/drm/i915/i915_gpu_error.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 1f2f266f26af..7118ecb7f144 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1007,67 +1007,67 @@ i915_error_object_create(struct drm_i915_private *i915,
 	compress->wc = i915_gem_object_is_lmem(vma->obj) ||
 		       drm_mm_node_allocated(&ggtt->error_capture);
 
 	ret = -EINVAL;
 	if (drm_mm_node_allocated(&ggtt->error_capture)) {
 		void __iomem *s;
 		dma_addr_t dma;
 
 		for_each_sgt_daddr(dma, iter, vma->pages) {
 			ggtt->vm.insert_page(&ggtt->vm, dma, slot,
 					     I915_CACHE_NONE, 0);
 
 			s = io_mapping_map_wc(&ggtt->iomap, slot, PAGE_SIZE);
 			ret = compress_page(compress, (void  __force *)s, dst);
 			io_mapping_unmap(s);
 			if (ret)
 				break;
 		}
 	} else if (i915_gem_object_is_lmem(vma->obj)) {
 		struct intel_memory_region *mem = vma->obj->mm.region;
 		dma_addr_t dma;
 
 		for_each_sgt_daddr(dma, iter, vma->pages) {
 			void __iomem *s;
 
-			s = io_mapping_map_atomic_wc(&mem->iomap, dma);
+			s = io_mapping_map_wc(&mem->iomap, dma, PAGE_SIZE);
 			ret = compress_page(compress, (void __force *)s, dst);
-			io_mapping_unmap_atomic(s);
+			io_mapping_unmap(s);
 			if (ret)
 				break;
 		}
 	} else {
 		struct page *page;
 
 		for_each_sgt_page(page, iter, vma->pages) {
 			void *s;
 
 			drm_clflush_pages(&page, 1);
 
-			s = kmap_atomic(page);
+			s = kmap(page);
 			ret = compress_page(compress, s, dst);
-			kunmap_atomic(s);
+			kunmap(s);
 
 			drm_clflush_pages(&page, 1);
 
 			if (ret)
 				break;
 		}
 	}
 
 	if (ret || compress_flush(compress, dst)) {
 		while (dst->page_count--)
 			pool_free(&compress->pool, dst->pages[dst->page_count]);
 		kfree(dst);
 		dst = NULL;
 	}
 	compress_finish(compress);
 
 	return dst;
 }
 
 /*
  * Generate a semi-unique error code. The code is not meant to have meaning, The
  * code's only purpose is to try to prevent false duplicated bug reports by
  * grossly estimating a GPU error state.
  *
  * TODO Ideally, hashing the batchbuffer would be a very nice way to determine
-- 
2.24.0