KVM: MMU: Add validate_direct_spte() helper
Add a helper to verify that a direct shadow page is valid wrt the required
access permissions; drop the page if it is not valid.
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b75d6cb..36c62f3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1500,6 +1500,29 @@
}
}
+static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
+ unsigned direct_access)
+{
+ if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
+ struct kvm_mmu_page *child;
+
+ /*
+ * For the direct sp, if the guest pte's dirty bit
+ * changed form clean to dirty, it will corrupt the
+ * sp's access: allow writable in the read-only sp,
+ * so we should update the spte at this point to get
+ * a new sp with the correct access.
+ */
+ child = page_header(*sptep & PT64_BASE_ADDR_MASK);
+ if (child->role.access == direct_access)
+ return;
+
+ mmu_page_remove_parent_pte(child, sptep);
+ __set_spte(sptep, shadow_trap_nonpresent_pte);
+ kvm_flush_remote_tlbs(vcpu->kvm);
+ }
+}
+
static void kvm_mmu_page_unlink_children(struct kvm *kvm,
struct kvm_mmu_page *sp)
{
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 0fb7068..0c7461d 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -338,30 +338,15 @@
break;
}
- if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
- struct kvm_mmu_page *child;
-
- if (level != gw->level)
- continue;
-
- /*
- * For the direct sp, if the guest pte's dirty bit
- * changed form clean to dirty, it will corrupt the
- * sp's access: allow writable in the read-only sp,
- * so we should update the spte at this point to get
- * a new sp with the correct access.
- */
- child = page_header(*sptep & PT64_BASE_ADDR_MASK);
- if (child->role.access == direct_access)
- continue;
-
- mmu_page_remove_parent_pte(child, sptep);
- __set_spte(sptep, shadow_trap_nonpresent_pte);
- kvm_flush_remote_tlbs(vcpu->kvm);
- }
+ if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)
+ && level == gw->level)
+ validate_direct_spte(vcpu, sptep, direct_access);
drop_large_spte(vcpu, sptep);
+ if (is_shadow_present_pte(*sptep))
+ continue;
+
if (level <= gw->level) {
direct = 1;
access = direct_access;