For device memory (aka VM_IO | VM_PFNMAP) MAP_POPULATE does nothing. Allow to use that for initializing the device memory by providing a new callback f_ops->populate() for the purpose.
SGX patches are provided to show the callback in context.
An obvious alternative is a ioctl but it is less elegant and requires two syscalls (mmap + ioctl) per memory range, instead of just one (mmap).
Jarkko Sakkinen (3): mm: Add f_ops->populate() x86/sgx: Export sgx_encl_page_alloc() x86/sgx: Implement EAUG population with MAP_POPULATE
arch/mips/kernel/vdso.c | 2 +- arch/x86/kernel/cpu/sgx/driver.c | 129 +++++++++++++++++++++ arch/x86/kernel/cpu/sgx/encl.c | 38 ++++++ arch/x86/kernel/cpu/sgx/encl.h | 3 + arch/x86/kernel/cpu/sgx/ioctl.c | 38 ------ drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 +- fs/coda/file.c | 2 +- fs/overlayfs/file.c | 2 +- include/linux/fs.h | 12 +- include/linux/mm.h | 2 +- ipc/shm.c | 2 +- mm/mmap.c | 10 +- mm/nommu.c | 4 +- 13 files changed, 193 insertions(+), 53 deletions(-)