Our error states are quickly growing, pinning kernel memory with them.
The majority of the space is taken up by the error objects. These
compress well using zlib and without decode are mostly meaningless, so
encoding them does not hinder quickly parsing the error state for
familiarity.

v2: Make the zlib dependency optional

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
---
 drivers/gpu/drm/i915/Kconfig          |  12 +++
 drivers/gpu/drm/i915/i915_drv.h       |   3 +-
 drivers/gpu/drm/i915/i915_gpu_error.c | 176 ++++++++++++++++++++++++++++++----
 3 files changed, 169 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 0f46a9c04c0e..92ecced1bc8f 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -57,6 +57,18 @@ config DRM_I915_CAPTURE_ERROR
 
          If in doubt, say "Y".
 
+config DRM_I915_COMPRESS_ERROR
+       bool "Compress GPU error state"
+       depends on DRM_I915_CAPTURE_ERROR
+       select ZLIB_DEFLATE
+       default y
+       help
+         This option selects ZLIB_DEFLATE if it isn't already
+         selected and causes any error state captured upon a GPU hang
+         to be compressed using zlib.
+
+         If in doubt, say "Y".
+
 config DRM_I915_USERPTR
        bool "Always enable userptr support"
        depends on DRM_I915
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 97203da3a08d..3d46f57eed3f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -820,9 +820,10 @@ struct drm_i915_error_state {
                struct intel_instdone instdone;
 
                struct drm_i915_error_object {
-                       int page_count;
                        u64 gtt_offset;
                        u64 gtt_size;
+                       int page_count;
+                       int unused;
                        u32 *pages[0];
                } *ringbuffer, *batchbuffer, *wa_batchbuffer, *ctx, *hws_page;
 
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c 
b/drivers/gpu/drm/i915/i915_gpu_error.c
index bf2498297341..6c22be28ba01 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -29,6 +29,7 @@
 
 #include <generated/utsrelease.h>
 #include <linux/stop_machine.h>
+#include <linux/zlib.h>
 #include "i915_drv.h"
 
 #ifdef CONFIG_DRM_I915_CAPTURE_ERROR
@@ -175,6 +176,110 @@ static void i915_error_puts(struct 
drm_i915_error_state_buf *e,
 #define err_printf(e, ...) i915_error_printf(e, __VA_ARGS__)
 #define err_puts(e, s) i915_error_puts(e, s)
 
+#ifdef CONFIG_DRM_I915_COMPRESS_ERROR
+
+static bool compress_init(struct z_stream_s *zstream)
+{
+       memset(zstream, 0, sizeof(*zstream));
+
+       zstream->workspace =
+               kmalloc(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
+                       GFP_ATOMIC | __GFP_NOWARN);
+       if (!zstream->workspace)
+               return false;
+
+       if (zlib_deflateInit(zstream, Z_DEFAULT_COMPRESSION) != Z_OK) {
+               kfree(zstream->workspace);
+               return false;
+       }
+
+       return true;
+}
+
+static int compress_page(struct z_stream_s *zstream,
+                        void *src,
+                        struct drm_i915_error_object *dst)
+{
+       zstream->next_in = src;
+       zstream->avail_in = PAGE_SIZE;
+
+       do {
+               if (zstream->avail_out == 0) {
+                       unsigned long page;
+
+                       page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
+                       if (!page)
+                               return -ENOMEM;
+
+                       dst->pages[dst->page_count++] = (void *)page;
+
+                       zstream->next_out = (void *)page;
+                       zstream->avail_out = PAGE_SIZE;
+               }
+
+               if (zlib_deflate(zstream, Z_SYNC_FLUSH) != Z_OK)
+                       return -EIO;
+       } while (zstream->avail_in);
+
+       /* Fallback to uncompressed if we increase size? */
+       if (0 && zstream->total_out > zstream->total_in)
+               return -E2BIG;
+
+       return 0;
+}
+
+static void compress_fini(struct z_stream_s *zstream,
+                         struct drm_i915_error_object *dst)
+{
+       if (dst) {
+               zlib_deflate(zstream, Z_FINISH);
+               dst->unused = zstream->avail_out;
+       }
+
+       zlib_deflateEnd(zstream);
+       kfree(zstream->workspace);
+}
+
+static void err_compression_marker(struct drm_i915_error_state_buf *m)
+{
+       err_puts(m, ":");
+}
+
+#else
+
+static bool compress_init(struct z_stream_s *zstream)
+{
+       return true;
+}
+
+static int compress_page(struct z_stream_s *zstream,
+                        void *src,
+                        struct drm_i915_error_object *dst)
+{
+       unsigned long page;
+
+       page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
+       if (!page)
+               return -ENOMEM;
+
+       dst->pages[dst->page_count++] =
+               memcpy((void *)page, src, PAGE_SIZE);
+
+       return 0;
+}
+
+static void compress_fini(struct z_stream_s *zstream,
+                         struct drm_i915_error_object *dst)
+{
+}
+
+static void err_compression_marker(struct drm_i915_error_state_buf *m)
+{
+       err_puts(m, "~");
+}
+
+#endif
+
 static void print_error_buffers(struct drm_i915_error_state_buf *m,
                                const char *name,
                                struct drm_i915_error_buffer *err,
@@ -342,12 +447,36 @@ void i915_error_printf(struct drm_i915_error_state_buf 
*e, const char *f, ...)
        va_end(args);
 }
 
+static int
+ascii85_encode_len(int len)
+{
+       return DIV_ROUND_UP(len, 4);
+}
+
+static bool
+ascii85_encode(u32 in, char *out)
+{
+       int i;
+
+       if (in == 0)
+               return false;
+
+       out[5] = '\0';
+       for (i = 5; i--; ) {
+               out[i] = '!' + in % 85;
+               in /= 85;
+       }
+
+       return true;
+}
+
 static void print_error_obj(struct drm_i915_error_state_buf *m,
                            struct intel_engine_cs *engine,
                            const char *name,
                            struct drm_i915_error_object *obj)
 {
-       int page, offset, elt;
+       char out[6];
+       int page;
 
        if (!obj)
                return;
@@ -359,13 +488,23 @@ static void print_error_obj(struct 
drm_i915_error_state_buf *m,
                           lower_32_bits(obj->gtt_offset));
        }
 
-       for (page = offset = 0; page < obj->page_count; page++) {
-               for (elt = 0; elt < PAGE_SIZE/4; elt++) {
-                       err_printf(m, "%08x :  %08x\n", offset,
-                                  obj->pages[page][elt]);
-                       offset += 4;
+       err_compression_marker(m);
+       for (page = 0; page < obj->page_count; page++) {
+               int i, len;
+
+               len = PAGE_SIZE;
+               if (page == obj->page_count - 1)
+                       len -= obj->unused;
+               len = ascii85_encode_len(len);
+
+               for (i = 0; i < len; i++) {
+                       if (ascii85_encode(obj->pages[page][i], out))
+                               err_puts(m, out);
+                       else
+                               err_puts(m, "z");
                }
        }
+       err_puts(m, "\n");
 }
 
 static void err_print_capabilities(struct drm_i915_error_state_buf *m,
@@ -645,20 +784,6 @@ static void i915_error_state_free(struct kref *error_ref)
        kfree(error);
 }
 
-static int compress_page(void *src, struct drm_i915_error_object *dst)
-{
-       unsigned long page;
-
-       page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
-       if (!page)
-               return -ENOMEM;
-
-       dst->pages[dst->page_count++] = (void *)page;
-
-       memcpy((void *)page, src, PAGE_SIZE);
-       return 0;
-}
-
 static struct drm_i915_error_object *
 i915_error_object_create(struct drm_i915_private *i915,
                         struct i915_vma *vma)
@@ -666,6 +791,7 @@ i915_error_object_create(struct drm_i915_private *i915,
        struct i915_ggtt *ggtt = &i915->ggtt;
        const u64 slot = ggtt->error_capture.start;
        struct drm_i915_error_object *dst;
+       struct z_stream_s zstream;
        unsigned long num_pages;
        struct sgt_iter iter;
        dma_addr_t dma;
@@ -674,6 +800,7 @@ i915_error_object_create(struct drm_i915_private *i915,
                return NULL;
 
        num_pages = min_t(u64, vma->size, vma->obj->base.size) >> PAGE_SHIFT;
+       num_pages = DIV_ROUND_UP(10 * num_pages, 8); /* worstcase zlib growth */
        dst = kmalloc(sizeof(*dst) + num_pages * sizeof(u32 *),
                      GFP_ATOMIC | __GFP_NOWARN);
        if (!dst)
@@ -682,6 +809,12 @@ i915_error_object_create(struct drm_i915_private *i915,
        dst->gtt_offset = vma->node.start;
        dst->gtt_size = vma->node.size;
        dst->page_count = 0;
+       dst->unused = 0;
+
+       if (!compress_init(&zstream)) {
+               kfree(dst);
+               return NULL;
+       }
 
        for_each_sgt_dma(dma, iter, vma->pages) {
                void __iomem *s;
@@ -691,7 +824,7 @@ i915_error_object_create(struct drm_i915_private *i915,
                                       I915_CACHE_NONE, 0);
 
                s = io_mapping_map_atomic_wc(&ggtt->mappable, slot);
-               ret = compress_page((void * __force)s, dst);
+               ret = compress_page(&zstream, (void  __force *)s, dst);
                io_mapping_unmap_atomic(s);
 
                if (ret)
@@ -706,6 +839,7 @@ unwind:
        dst = NULL;
 
 out:
+       compress_fini(&zstream, dst);
        ggtt->base.clear_range(&ggtt->base, slot, PAGE_SIZE, true);
        return dst;
 }
-- 
2.9.3

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