Hi Andy, On Wed, Jul 17, 2019 at 02:24:09PM -0700, Andy Lutomirski wrote: > On Wed, Jul 17, 2019 at 12:14 AM Joerg Roedel <joro@xxxxxxxxxx> wrote: > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 4fa8d84599b0..322b11a374fd 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -132,6 +132,8 @@ static void vunmap_page_range(unsigned long addr, unsigned long end) > > continue; > > vunmap_p4d_range(pgd, addr, next); > > } while (pgd++, addr = next, addr != end); > > + > > + vmalloc_sync_all(); > > } > > I'm confused. Shouldn't the code in _vm_unmap_aliases handle this? > As it stands, won't your patch hurt performance on x86_64? If x86_32 > is a special snowflake here, maybe flush_tlb_kernel_range() should > handle this? Imo this is the logical place to handle this. The code first unmaps the area from the init_mm page-table and then syncs that page-table to all other page-tables in the system, so one place to update the page-tables. Performance-wise it makes no difference if we put that into _vm_unmap_aliases(), as that is called in the vmunmap path too. But it is right that vmunmap/iounmap performance on x86-64 will decrease to some degree. If that is a problem for some workloads I can also implement a complete separate code-path which just syncs unmappings and is only implemented for x86-32 with !SHARED_KERNEL_PMD. Regards, Joerg
