KVM: MMU: improve write flooding detected
Detecting write-flooding does not work well, when we handle page written, if
the last speculative spte is not accessed, we treat the page is
write-flooding, however, we can speculative spte on many path, such as pte
prefetch, page synced, that means the last speculative spte may be not point
to the written page and the written page can be accessed via other sptes, so
depends on the Accessed bit of the last speculative spte is not enough
Instead of detected page accessed, we can detect whether the spte is accessed
after it is written, if the spte is not accessed but it is written frequently,
we treat is not a page table or it not used for a long time
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 9efb860..52e9d58 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -497,6 +497,7 @@
shadow_walk_next(&it)) {
gfn_t table_gfn;
+ clear_sp_write_flooding_count(it.sptep);
drop_large_spte(vcpu, it.sptep);
sp = NULL;
@@ -522,6 +523,7 @@
shadow_walk_next(&it)) {
gfn_t direct_gfn;
+ clear_sp_write_flooding_count(it.sptep);
validate_direct_spte(vcpu, it.sptep, direct_access);
drop_large_spte(vcpu, it.sptep);
@@ -536,6 +538,7 @@
link_shadow_page(it.sptep, sp);
}
+ clear_sp_write_flooding_count(it.sptep);
mmu_set_spte(vcpu, it.sptep, access, gw->pte_access,
user_fault, write_fault, emulate, it.level,
gw->gfn, pfn, prefault, map_writable);
@@ -599,11 +602,9 @@
*/
if (!r) {
pgprintk("%s: guest page fault\n", __func__);
- if (!prefault) {
+ if (!prefault)
inject_page_fault(vcpu, &walker.fault);
- /* reset fork detector */
- vcpu->arch.last_pt_write_count = 0;
- }
+
return 0;
}
@@ -641,9 +642,6 @@
pgprintk("%s: shadow pte %p %llx emulate %d\n", __func__,
sptep, *sptep, emulate);
- if (!emulate)
- vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
-
++vcpu->stat.pf_fixed;
trace_kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
spin_unlock(&vcpu->kvm->mmu_lock);