On Wed, Dec 14, 2022 at 10:51:31AM +0000, "Huang, Kai" <kai.huang@xxxxxxxxx> wrote: > On Sat, 2022-10-29 at 23:22 -0700, isaku.yamahata@xxxxxxxxx wrote: > > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > > kvm_unmap_gfn_range() needs to know the reason of the callback for TDX. > > mmu notifier, set memattr ioctl or restrictedmem notifier. Based on the > > reason, TDX changes the behavior. For mmu notifier, it's the operation on > > shared memory slot to zap shared PTE. For set memattr, private<->shared > > conversion, zap the original PTE. For restrictedmem, it's a hint that TDX > > can ignore. > > Could you elaborate why restricted memfd notifier can be ignored? IIUC if > userspace punch a hole, the pages within the hole will be de-allocated. So why > can such notifier be ignored? Because set-memory-attribute ioctl is expected to follow the callback from restrictedmem. So set memory attributes can do de-allocation. I wanted to avoid zapping twice. With v9 UPM, the restrictedmem callback was triggered for both allocation and punch-hole. With v10 UPM, the callback is triggered only for punch-hole. With v10 callback semantics, probably this can be cleaned up slightly. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
