On Sun, Sep 10, 2023 at 02:36:40PM -0600, Jonathan Corbet wrote: > Gregory Price <gourry.memverge@xxxxxxxxx> writes: > > > Similar to the move_pages system call, instead of taking a pid and > > list of virtual addresses, this system call takes a list of physical > > addresses. > > > > Because there is no task to validate the memory policy against, each > > page needs to be interrogated to determine whether the migration is > > valid, and all tasks that map it need to be interrogated. > > > > This is accomplished via an rmap_walk on the folio containing > > the page, and interrogating all tasks that map the page. > > > > Each page must be interrogated individually, which should be > > considered when using this to migrate shared regions. > > > > The remaining logic is the same as the move_pages syscall. One > > change to do_pages_move is made (to check whether an mm_struct is > > passed) in order to re-use the existing migration code. > > > > Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx> > > --- > > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > > include/linux/syscalls.h | 5 + > > include/uapi/asm-generic/unistd.h | 8 +- > > kernel/sys_ni.c | 1 + > > mm/migrate.c | 178 +++++++++++++++++++++++- > > tools/include/uapi/asm-generic/unistd.h | 8 +- > > 7 files changed, 197 insertions(+), 5 deletions(-) > > So this is probably a silly question, but just to be sure ... what is > the permission model for this system call? As far as I can tell, the > ability to move pages is entirely unrestricted, with the exception of > pages that would need MPOL_MF_MOVE_ALL. If so, that seems undesirable, > but probably I'm just missing something ... ? > > Thanks, > > jon Not silly, looks like when U dropped the CAP_SYS_NICE check (no task to check against), check i neglected to add a CAP_SYS_ADMIN check. Oversight on my part, I'll work it in with other feedback. Thanks! ~Gregory
