On Fri, Sep 22, 2023 at 05:00:40PM +0100, Catalin Marinas wrote: > On Fri, Aug 25, 2023 at 10:35:26AM +0100, Shameer Kolothum wrote: > > From: Keqian Zhu <zhukeqian1@xxxxxxxxxx> > > > > This function write protects all PTEs between the ffs and fls of mask. > > There may be unset bits between this range. It works well under pure > > software dirty log, as software dirty log is not working during this > > process. > > > > But it will unexpectly clear dirty status of PTE when hardware dirty > > log is enabled. So change it to only write protect selected PTE. > > Ah, I did wonder about losing the dirty status. The equivalent to S1 > would be for kvm_pgtable_stage2_wrprotect() to set a software dirty bit. > > I'm only superficially familiar with how KVM does dirty tracking for > live migration. Does it need to first write-protect the pages and > disable DBM? Is DBM re-enabled later? Or does stage2_wp_range() with > your patches leave the DBM on? If the latter, the 'wp' aspect is a bit > confusing since DBM basically means writeable (and maybe clean). So > better to have something like stage2_clean_range(). KVM has never enabled DBM and we solely rely on write-protection faults for dirty tracking. IOW, we do not have a writable-clean state for stage-2 PTEs (yet). -- Thanks, Oliver
