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Subject[PATCH 22/25] KVM: opencode gfn_to_page in kvm_vm_fault
Date
From: Marcelo Tosatti <mtosatti@redhat.com>

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>
---
virt/kvm/kvm_main.c | 19 ++++++++++++-------
1 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f42d5c2..2907d05 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;
}

--
1.6.0.1


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