KVM: MMU: introduce gfn_to_page_many_atomic() function

Introduce this function to get consecutive gfn's pages, it can reduce
gup's overload, used by later patch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 31 insertions, 1 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 307d0e2c0f59..b837ec80885d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -289,6 +289,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 void kvm_disable_largepages(void);
 void kvm_arch_flush_shadow(struct kvm *kvm);
 
+int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
+                            int nr_pages);
+
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
 void kvm_release_page_clean(struct page *page);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 08bd304f8bc7..2eb0b7500a2a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -927,15 +927,25 @@ int memslot_id(struct kvm *kvm, gfn_t gfn)
         return memslot - slots->memslots;
 }
 
-unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
+static unsigned long gfn_to_hva_many(struct kvm *kvm, gfn_t gfn,
+                                     gfn_t *nr_pages)
 {
         struct kvm_memory_slot *slot;
 
         slot = gfn_to_memslot(kvm, gfn);
         if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                 return bad_hva();
+
+        if (nr_pages)
+                *nr_pages = slot->npages - (gfn - slot->base_gfn);
+
         return gfn_to_hva_memslot(slot, gfn);
 }
+
+unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
+{
+        return gfn_to_hva_many(kvm, gfn, NULL);
+}
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
 static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
@@ -1010,6 +1020,23 @@ pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
         return hva_to_pfn(kvm, addr, false);
 }
 
+int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
+                                                                  int nr_pages)
+{
+        unsigned long addr;
+        gfn_t entry;
+
+        addr = gfn_to_hva_many(kvm, gfn, &entry);
+        if (kvm_is_error_hva(addr))
+                return -1;
+
+        if (entry < nr_pages)
+                return 0;
+
+        return __get_user_pages_fast(addr, nr_pages, 1, pages);
+}
+EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);
+
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
         pfn_t pfn;