Messages in this thread | | | Date | Fri, 2 Mar 2012 12:16:47 -0800 | Subject | Re: [Pkg-xen-devel] ioatdma: Boot process hangs then reboots when using Xen + Linux 3.2 | From | Dan Williams <> |
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On Fri, Mar 2, 2012 at 12:08 PM, Bastian Blank <waldi@debian.org> wrote: > On Fri, Mar 02, 2012 at 11:31:56AM -0800, Dan Williams wrote: >> On Fri, Mar 2, 2012 at 9:57 AM, Bastian Blank <waldi@debian.org> wrote: >> > phys_complete (a 32 bit value) gets compared to struct >> > dma_async_tx_descriptor.phys, which is defined as dma_addr_t, a _64_ bit >> > value. >> The assumption is that the driver's control structures are not in high >> memory so all address values will only have 32-bits of valid data, > > Can you back that up by some kernel documentation? There is a reason why > pci_alloc_pool uses dma_addr_t to store the address and _not_ unsigned > long. This are physical addresses, nothing the kernel can access > directly without a mapping.
High memory can only be accessed with kmap(), so the assumption is that dma_alloc never gives a buffer address above 32-bits on a 32-bit build. Yes, if HIGHMEM64G is set dma_addr_t becomes 64-bit, but that is only to access high memory mapped application buffers via dma_map. I'm not aware of any documentation in this area.
I don't mind bumping up the size if xen32 is changing the above assumptions, but I'd want confirmation that this is the failure scenario.
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