From a30f47cb150dd8d109923eeb65fe73e8b3e09046 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Thu, 22 Sep 2011 16:58:36 +0800 Subject: 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 Signed-off-by: Avi Kivity --- arch/x86/kvm/paging_tmpl.h | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) (limited to 'arch/x86/kvm/paging_tmpl.h') diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 9efb86035774..52e9d58cec2b 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -497,6 +497,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 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 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 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 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 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 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, */ 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 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, 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); -- cgit