On Wed, Jul 06, 2011 at 09:22:28AM +0800, Xiao Guangrong wrote: > On 07/06/2011 03:27 AM, Marcelo Tosatti wrote: > > On Thu, Jun 30, 2011 at 04:21:30PM +0800, Xiao Guangrong wrote: > >> If dirty bit is not set, we can make the pte access read-only to avoid handing > >> dirty bit everywhere > >> > >> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx> > > > >> -static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte) > >> +static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte, > >> + bool last) > >> { > >> unsigned access; > >> > >> access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK; > >> + if (last && !is_dirty_gpte(gpte)) > >> + access &= ~ACC_WRITE_MASK; > >> + > > > > What if the walker marks the dirty bit on the gpte? > > > > Actually, we get guest pte access after mark the dirty bit: > > if (write_fault && unlikely(!is_dirty_gpte(pte))) { > int ret; > > trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte)); > ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, > pte, pte|PT_DIRTY_MASK); > if (unlikely(ret < 0)) { > present = false; > goto error; > } else if (ret) > goto walk; > > mark_page_dirty(vcpu->kvm, table_gfn); > pte |= PT_DIRTY_MASK; > walker->ptes[walker->level - 1] = pte; > } > > pte_access = pt_access & FNAME(gpte_access)(vcpu, pte, true); > > So, i think it works well :-) I think you meant after marking the accessed bit. The dirty bit is set just before returning. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html