* Andrew Jones (drjo...@redhat.com) wrote: > On Wed, Sep 09, 2020 at 06:45:33PM -0700, Richard Henderson wrote: > > On 9/9/20 8:25 AM, Andrew Jones wrote: > > >> * Provide a KVM-specific method to extract the tags from guest memory. > > >> This might also have benefits in terms of providing an easy way to > > >> read bulk tag data from guest memory (since the LDGM instruction > > >> isn't available at EL0). > > > > > > Maybe we need a new version of KVM_GET_DIRTY_LOG that also provides > > > the tags for all addresses of each dirty page. > > > > KVM_GET_DIRTY_LOG just provides one bit per dirty page, no? Then VMM copies > > the data out from its local address to guest memory. > > > > There'd be no difference with or without tags, afaik. It's just about how > > VMM > > copies the data, with or without tags. > > Right, as long as it's fast enough to do > > for_each_dirty_page(page, dirty_log) > for (i = 0; i < host-page-size/16; i += 16) > append_tag(LDG(page + i)) > > to get all the tags for each dirty page. I understood it would be faster > to use LDGM, but we'd need a new ioctl for that. So I was proposing we > just piggyback on a new dirty-log ioctl instead.
That feels a bad idea to me; there's a couple of different ways dirty page checking work; lets keep extracting the tags separate. Dave > Thanks, > drew -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
