On 2019-01-10 3:48 p.m., Christoph Hellwig wrote: > On Thu, Jan 10, 2019 at 03:00:31PM +0100, Christian König wrote: >>> From the trace it looks like we git the case where swiotlb tries >>> to copy back data from a bounce buffer, but hits a dangling or NULL >>> pointer. So a couple questions for the submitter: >>> >>> - does the system have more than 4GB memory and thus use swiotlb? >>> (check /proc/meminfo, and if something SWIOTLB appears in dmesg) >>> - does the device this happens on have a DMA mask smaller than >>> the available memory, that is should swiotlb be used here to start >>> with? >> >> Rather unlikely. The device is an AMD GPU, so we can address memory up to >> 1TB. > > So we probably somehow got a false positive. > > For now I'like the reported to confirm that the dma_direct_unmap_page+0x92 > backtrace really is in the swiotlb code (I can't think of anything else, > but I'd rather be sure). > > Second it would be great to print what the contents of io_tlb_start > and io_tlb_end are, e.g. by doing a printk_once in is_swiotlb_buffer, > maybe that gives a clue why we are hitting the swiotlb code here. Any progress? https://bugzilla.kernel.org/show_bug.cgi?id=202261 was also filed about this. I hope everyone's clear that this needs to be resolved one way or another by 5.0 final (though the sooner, the better :). -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
