On Fri, May 26, 2017 at 10:24:38AM +0800, Haozhong Zhang wrote: > file_ram_alloc() currently maps the backend file via mmap to a virtual > address aligned to the value returned by qemu_fd_getpagesize(). When a > DAX device (e.g. /dev/dax0.0) is used as the backend file, its kernel > mmap implementation may require an alignment larger than what > qemu_fd_get_pagesize() returns (e.g. 2MB vs. 4KB), and mmap may fail. > > This commit adds an attribute 'align' to hostmem-file, so that users > can specify a proper alignment that satisfies the kernel requirement. > > If 'align' is not specified or is 0, the value returned by > qemu_fd_get_pagesize() will be used as before.
How are users supposed to determine alignment requirements?
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