[Mesa-dev] [PATCH 2/2] winsys/svga: Limit the maximum DMA hardware buffer size

Thomas Hellström (VMware) thomas_os at shipmail.org
Wed Oct 9 12:41:41 UTC 2019

From: Thomas Hellstrom <thellstrom at vmware.com>

The kernel total GMR/DMA size is limited, but it's definitely possible for the
kernel to allow a larger buffer allocation to succeed, but command
submission using that buffer as a GMR would fail typically causing an
application crash.

So have the winsys limit the size of GMR/DMA buffers. The pipe driver will
then resort to allocating smaller buffers and perform the DMA transfer in
multiple bands, also allowing for the pre-flush mechanism to kick in.

This avoids the related application crashes.

Fixes: e7843273fae ("winsys/svga: Update to vmwgfx kernel module 2.1")
Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
Reviewed-by: Brian Paul <brianp at vmware.com>
Reviewed-by: Charmaine Lee <charmainel at vmware.com>
Reviewed-by: Roland Scheidegger <sroland at vmware.com>
 src/gallium/winsys/svga/drm/vmw_screen_svga.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/gallium/winsys/svga/drm/vmw_screen_svga.c b/src/gallium/winsys/svga/drm/vmw_screen_svga.c
index cd3f21f6033..fb0bee77822 100644
--- a/src/gallium/winsys/svga/drm/vmw_screen_svga.c
+++ b/src/gallium/winsys/svga/drm/vmw_screen_svga.c
@@ -80,8 +80,11 @@ vmw_svga_winsys_buffer_create(struct svga_winsys_screen *sws,
       provider = vws->pools.query_fenced;
    } else if (usage == SVGA_BUFFER_USAGE_SHADER) {
       provider = vws->pools.mob_shader_slab_fenced;
-   } else
+   } else {
+      if (size > VMW_GMR_POOL_SIZE)
+         return NULL;
       provider = vws->pools.gmr_fenced;
+   }
    buffer = provider->create_buffer(provider, size, &desc.pb_desc);

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