KVM: Change kvm_{read,write}_guest() to use copy_{from,to}_user()

This changes kvm_write_guest_page/kvm_read_guest_page to use
copy_to_user/read_from_user, as a result we get better speed
and better dirty bit tracking.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 14 insertions, 24 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 04544aecf22..d68901bd069 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -630,20 +630,15 @@ static int next_segment(unsigned long len, int offset)
 int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
                         int len)
 {
-        void *page_virt;
-        struct page *page;
+        int r;
+        unsigned long addr;
 
-        page = gfn_to_page(kvm, gfn);
-        if (is_error_page(page)) {
-                kvm_release_page(page);
+        addr = gfn_to_hva(kvm, gfn);
+        if (kvm_is_error_hva(addr))
+                return -EFAULT;
+        r = copy_from_user(data, (void __user *)addr + offset, len);
+        if (r)
                 return -EFAULT;
-        }
-        page_virt = kmap_atomic(page, KM_USER0);
-
-        memcpy(data, page_virt + offset, len);
-
-        kunmap_atomic(page_virt, KM_USER0);
-        kvm_release_page(page);
         return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_read_guest_page);
@@ -671,21 +666,16 @@ EXPORT_SYMBOL_GPL(kvm_read_guest);
 int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
                          int offset, int len)
 {
-        void *page_virt;
-        struct page *page;
+        int r;
+        unsigned long addr;
 
-        page = gfn_to_page(kvm, gfn);
-        if (is_error_page(page)) {
-                kvm_release_page(page);
+        addr = gfn_to_hva(kvm, gfn);
+        if (kvm_is_error_hva(addr))
+                return -EFAULT;
+        r = copy_to_user((void __user *)addr + offset, data, len);
+        if (r)
                 return -EFAULT;
-        }
-        page_virt = kmap_atomic(page, KM_USER0);
-
-        memcpy(page_virt + offset, data, len);
-
-        kunmap_atomic(page_virt, KM_USER0);
         mark_page_dirty(kvm, gfn);
-        kvm_release_page(page);
         return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_write_guest_page);