On 13/06/2018 00:52, Junaid Shahid wrote: > sp = page_header(root); > + > + /* > + * Even if another VCPU was marking the SP as unsync-ed > + * simultaneously, any guest page table changes are not > + * guaranteed to be visible anyway until this VCPU issues a TLB > + * flush strictly after those changes are made. We only need to > + * ensure that the other CPU sets these flags before any actual > + * changes to the page tables are made. The comments in > + * mmu_need_write_protect() describe what could go wrong if this > + * requirement isn't satisfied. > + */ > + smp_rmb(); This is actually an smp_read_barrier_depends(), which is possibly more self-documenting. I can do the replacement myself. Paolo > + if (!sp->unsync && !sp->unsync_children) > + return; > +
