From 38187c830cab84daecb41169948467f1f19317e3 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Tue, 23 Sep 2008 13:18:32 -0300 Subject: [PATCH] KVM: MMU: do not write-protect large mappings 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 Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 23752ef0839c..731e6fe9cb07 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1180,11 +1180,16 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte, || (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 *vcpu, u64 *shadow_pte, if (pte_access & ACC_WRITE_MASK) mark_page_dirty(vcpu->kvm, gfn); +set_pte: set_shadow_pte(shadow_pte, spte); return ret; } -- 2.20.1