On Mon, Mar 4, 2024 at 10:05 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > vmap/vmalloc APIs are used to map a set of pages into contiguous kernel > virtual space. > > get_vm_area() with appropriate flag is used to request an area of kernel > address range. It's used for vmalloc, vmap, ioremap, xen use cases. > - vmalloc use case dominates the usage. Such vm areas have VM_ALLOC flag. > - the areas created by vmap() function should be tagged with VM_MAP. > - ioremap areas are tagged with VM_IOREMAP. > > BPF would like to extend the vmap API to implement a lazily-populated > sparse, yet contiguous kernel virtual space. Introduce VM_SPARSE flag > and vm_area_map_pages(area, start_addr, count, pages) API to map a set > of pages within a given area. > It has the same sanity checks as vmap() does. > It also checks that get_vm_area() was created with VM_SPARSE flag > which identifies such areas in /proc/vmallocinfo > and returns zero pages on read through /proc/kcore. > > The next commits will introduce bpf_arena which is a sparsely populated > shared memory region between bpf program and user space process. It will > map privately-managed pages into a sparse vm area with the following steps: > > // request virtual memory region during bpf prog verification > area = get_vm_area(area_size, VM_SPARSE); > > // on demand > vm_area_map_pages(area, kaddr, kend, pages); > vm_area_unmap_pages(area, kaddr, kend); > > // after bpf program is detached and unloaded > free_vm_area(area); > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
