Re: [PATCH RFC 0/3] MAP_POPULATE for device memory

On 06.03.22 06:32, Jarkko Sakkinen wrote:

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).

What about extending MADV_POPULATE_READ | MADV_POPULATE_WRITE to support VM_IO | VM_PFNMAP (as well?) ?