From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: [patch 04/13] KVM: MMU: do not write-protect large mappings Date: Mon, 22 Sep 2008 16:16:31 -0300 Message-ID: <20080922192215.089281008@localhost.localdomain> References: <20080922191627.671519725@localhost.localdomain> Cc: kvm@vger.kernel.org, Marcelo Tosatti To: Avi Kivity Return-path: Received: from mx2.redhat.com ([66.187.237.31]:40173 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752912AbYIVT0W (ORCPT ); Mon, 22 Sep 2008 15:26:22 -0400 Content-Disposition: inline; filename=no-wrprotect-large-parge Sender: kvm-owner@vger.kernel.org List-ID: There is not much point in write protecting large mappings. This can only happen when a page is shadowed during the window between is_largepage_backed and mmu_lock acquision. Zap the entry instead, so the next pagefault will find a shadowed page via is_largepage_backed and fallback to 4k translations. Simplifies out of sync shadow. Signed-off-by: Marcelo Tosatti Index: kvm/arch/x86/kvm/mmu.c =================================================================== --- kvm.orig/arch/x86/kvm/mmu.c +++ kvm/arch/x86/kvm/mmu.c @@ -1180,11 +1180,16 @@ static int set_spte(struct kvm_vcpu *vcp || (write_fault && !is_write_protection(vcpu) && !user_fault)) { struct kvm_mmu_page *shadow; + if (largepage && has_wrprotected_page(vcpu->kvm, gfn)) { + ret = 1; + spte = shadow_trap_nonpresent_pte; + goto set_pte; + } + spte |= PT_WRITABLE_MASK; shadow = kvm_mmu_lookup_page(vcpu->kvm, gfn); - if (shadow || - (largepage && has_wrprotected_page(vcpu->kvm, gfn))) { + if (shadow) { pgprintk("%s: found shadow page for %lx, marking ro\n", __func__, gfn); ret = 1; @@ -1197,6 +1202,7 @@ static int set_spte(struct kvm_vcpu *vcp if (pte_access & ACC_WRITE_MASK) mark_page_dirty(vcpu->kvm, gfn); +set_pte: set_shadow_pte(shadow_pte, spte); return ret; } --