[5/6] kvm, x86: use ro page and don't copy shared page

Commit Message

Lai Jiangshan July 16, 2010, 2:13 a.m. UTC

None

Patch

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8ba9b0d..6382140 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1832,6 +1832,45 @@  static void kvm_unsync_pages(struct kvm_vcpu *vcpu,  gfn_t gfn)
 	}
 }
 
+/* get a current mapped page fast, and test whether the page is writable. */
+static struct page *get_user_page_and_protection(unsigned long addr,
+	int *writable)
+{
+	struct page *page[1];
+
+	if (__get_user_pages_fast(addr, 1, 1, page) == 1) {
+		*writable = 1;
+		return page[0];
+	}
+	if (__get_user_pages_fast(addr, 1, 0, page) == 1) {
+		*writable = 0;
+		return page[0];
+	}
+	return NULL;
+}
+
+static pfn_t kvm_get_pfn_for_page_fault(struct kvm *kvm, gfn_t gfn,
+		int write_fault, int *host_writable)
+{
+	unsigned long addr;
+	struct page *page;
+
+	if (!write_fault) {
+		addr = gfn_to_hva(kvm, gfn);
+		if (kvm_is_error_hva(addr)) {
+			get_page(bad_page);
+			return page_to_pfn(bad_page);
+		}
+
+		page = get_user_page_and_protection(addr, host_writable);
+		if (page)
+			return page_to_pfn(page);
+	}
+
+	*host_writable = 1;
+	return kvm_get_pfn_for_gfn(kvm, gfn);
+}
+
 static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
 				  bool can_unsync)
 {
@@ -2085,6 +2124,7 @@  static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 	int level;
 	pfn_t pfn;
 	unsigned long mmu_seq;
+	int host_writable;
 
 	level = mapping_level(vcpu, gfn);
 
@@ -2099,7 +2139,7 @@  static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
-	pfn = kvm_get_pfn_for_gfn(vcpu->kvm, gfn);
+	pfn = kvm_get_pfn_for_page_fault(vcpu->kvm, gfn, write, &host_writable);
 
 	/* mmio */
 	if (is_error_pfn(pfn))
@@ -2109,7 +2149,7 @@  static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 	if (mmu_notifier_retry(vcpu, mmu_seq))
 		goto out_unlock;
 	kvm_mmu_free_some_pages(vcpu);
-	r = __direct_map(vcpu, v, write, level, gfn, pfn, true);
+	r = __direct_map(vcpu, v, write, level, gfn, pfn, host_writable);
 	spin_unlock(&vcpu->kvm->mmu_lock);
 
 
@@ -2307,6 +2347,8 @@  static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
 	int level;
 	gfn_t gfn = gpa >> PAGE_SHIFT;
 	unsigned long mmu_seq;
+	int write_fault = error_code & PFERR_WRITE_MASK;
+	int host_writable;
 
 	ASSERT(vcpu);
 	ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
@@ -2321,15 +2363,16 @@  static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
-	pfn = kvm_get_pfn_for_gfn(vcpu->kvm, gfn);
+	pfn = kvm_get_pfn_for_page_fault(vcpu->kvm, gfn, write_fault,
+			&host_writable);
 	if (is_error_pfn(pfn))
 		return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
 	spin_lock(&vcpu->kvm->mmu_lock);
 	if (mmu_notifier_retry(vcpu, mmu_seq))
 		goto out_unlock;
 	kvm_mmu_free_some_pages(vcpu);
-	r = __direct_map(vcpu, gpa, error_code & PFERR_WRITE_MASK,
-			 level, gfn, pfn, true);
+	r = __direct_map(vcpu, gpa, write_fault,
+			 level, gfn, pfn, host_writable);
 	spin_unlock(&vcpu->kvm->mmu_lock);
 
 	return r;
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index a9dbaa0..1874f51 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -430,6 +430,7 @@  static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	pfn_t pfn;
 	int level = PT_PAGE_TABLE_LEVEL;
 	unsigned long mmu_seq;
+	int host_writable;
 
 	pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
 	kvm_mmu_audit(vcpu, "pre page fault");
@@ -461,7 +462,8 @@  static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
-	pfn = kvm_get_pfn_for_gfn(vcpu->kvm, walker.gfn);
+	pfn = kvm_get_pfn_for_page_fault(vcpu->kvm, walker.gfn, write_fault,
+			&host_writable);
 
 	/* mmio */
 	if (is_error_pfn(pfn))
@@ -472,7 +474,7 @@  static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 		goto out_unlock;
 	kvm_mmu_free_some_pages(vcpu);
 	sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
-			     level, &write_pt, pfn, true);
+			     level, &write_pt, pfn, host_writable);
 	(void)sptep;
 	pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__,
 		 sptep, *sptep, write_pt);
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 738e659..a4ce19f 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -8,6 +8,7 @@ 
 #include <linux/mm.h>
 #include <linux/vmstat.h>
 #include <linux/highmem.h>
+#include <linux/module.h>
 
 #include <asm/pgtable.h>
 
@@ -274,6 +275,7 @@  int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 
 	return nr;
 }
+EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 
 /**
  * get_user_pages_fast() - pin user pages in memory