KVM: opencode gfn_to_page in kvm_vm_fault

kvm_vm_fault is invoked with mmap_sem held in read mode. Since gfn_to_page
will be converted to get_user_pages_fast, which requires this lock NOT
to be held, switch to opencoded get_user_pages.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f42d5c2a396d..2907d05cfcc3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1394,17 +1394,22 @@ out:
 
 static int kvm_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
+        struct page *page[1];
+        unsigned long addr;
+        int npages;
+        gfn_t gfn = vmf->pgoff;
         struct kvm *kvm = vma->vm_file->private_data;
-        struct page *page;
 
-        if (!kvm_is_visible_gfn(kvm, vmf->pgoff))
+        addr = gfn_to_hva(kvm, gfn);
+        if (kvm_is_error_hva(addr))
                 return VM_FAULT_SIGBUS;
-        page = gfn_to_page(kvm, vmf->pgoff);
-        if (is_error_page(page)) {
-                kvm_release_page_clean(page);
+
+        npages = get_user_pages(current, current->mm, addr, 1, 1, 0, page,
+                                NULL);
+        if (unlikely(npages != 1))
                 return VM_FAULT_SIGBUS;
-        }
-        vmf->page = page;
+
+        vmf->page = page[0];
         return 0;
 }