Messages in this thread | | | Subject | Re: Validating dma_mmap_coherent() parameters before calling (was Re: WARNING in memtype_reserve) | From | Jeremy Linton <> | Date | Thu, 14 May 2020 06:16:10 -0500 |
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On 5/14/20 6:14 AM, Christoph Hellwig wrote: > On Thu, May 14, 2020 at 06:10:03AM -0500, Jeremy Linton wrote: >>> I only need to look at the commit for 3 seconds to tell you that it is >>> completely buggy. While using dma_mmap_coherent is fundamentally the >>> right thing and absolutely required for dma_alloc_* allocations, USB >>> also uses it's own local gen pool allocator or plain kmalloc for not >>> DMA capable controller. This need to use remap_pfn_range. I'm pretty >>> sure you hit one of those cases. >> >> ? The code path in question is usbdev_mmap() and the allocation is done ~13 >> lines lines before as a usb_alloc_coherent(). > > And did you take a look at how usb_alloc_coherent is implemented? That > should make it completely obvious that not all allocations come > from dma_alloc_*.
No, your right, I noticed/remembered the usb_alloc vs dma_alloc difference right after sending that email, and was just about to say so.
Sorry, you right.
> >> That sort of makes sense, except for the above, and the fact that I would >> imagine the dma_mmap_coherent should be dealing with that case. I'm not >> really clear about the details of the GCE usb device here, but my first >> guess at this was the dma_pgprot() in dma_direct_mmap() is incorrectly >> picking a pgprot... > > No, dma_mmap_* / dma_direct_mmap has absolutely no business dealing > with memory that did not come from the DMA allocator. >
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