[RFC 6/8]KVM: introduce kvm_mmu_zap_pagetbl

[Shaohua Li <shaohua.li@intel.com>]

add a routine to zap all shadow pgtble for a gfn. If kvm supports SMP,
the API should zap pgtble for all vcpus, but kvm shadow page table
really should be per-vm, instead of per-vcpu.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
---
 drivers/kvm/kvm.h |    1 +
 drivers/kvm/mmu.c |   28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

Index: linux/drivers/kvm/kvm.h
===================================================================
--- linux.orig/drivers/kvm/kvm.h	2007-07-20 14:19:15.000000000 +0800
+++ linux/drivers/kvm/kvm.h	2007-07-20 14:26:10.000000000 +0800
@@ -621,6 +621,7 @@ int kvm_mmu_unprotect_page_virt(struct k
 void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
 int kvm_mmu_load(struct kvm_vcpu *vcpu);
 void kvm_mmu_unload(struct kvm_vcpu *vcpu);
+void kvm_mmu_zap_pagetbl(struct kvm_vcpu *vcpu, u64 gfn);
 
 int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
Index: linux/drivers/kvm/mmu.c
===================================================================
--- linux.orig/drivers/kvm/mmu.c	2007-07-20 14:25:25.000000000 +0800
+++ linux/drivers/kvm/mmu.c	2007-07-20 14:26:10.000000000 +0800
@@ -1324,6 +1324,34 @@ void kvm_mmu_zap_all(struct kvm_vcpu *vc
 	init_kvm_mmu(vcpu);
 }
 
+/* FIXME: this should zap all vcpu's shadow pgtbl for gfn */
+void kvm_mmu_zap_pagetbl(struct kvm_vcpu *vcpu, u64 gfn)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_rmap_desc *desc;
+	struct page *page;
+	u64 *spte;
+
+	page = gfn_to_page(kvm, gfn);
+	BUG_ON(!page);
+
+	while (page_private(page)) {
+		if (!(page_private(page) & 1))
+			spte = (u64 *)page_private(page);
+		else {
+			desc = (struct kvm_rmap_desc *)(page_private(page) & ~1ul);
+			spte = desc->shadow_ptes[0];
+		}
+		BUG_ON(!spte);
+		BUG_ON((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT
+			!= page_to_pfn(page));
+		BUG_ON(!(*spte & PT_PRESENT_MASK));
+		rmap_remove(vcpu, spte);
+		*spte = 0;
+	}
+	kvm_flush_remote_tlbs(vcpu->kvm);
+}
+
 void kvm_mmu_module_exit(void)
 {
 	if (pte_chain_cache)