KVM: introduce kvm_read_guest_offset_cached()

We already have kvm_write_guest_offset_cached(), introduce read analogue.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200525144125.143875-5-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1616846..f43b59b 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -734,6 +734,9 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
 int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
 int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                           void *data, unsigned long len);
+int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+                                void *data, unsigned int offset,
+                                unsigned long len);
 int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
                         int offset, int len);
 int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c9c6db5..e2af6ff 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2510,13 +2510,15 @@ int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 }
 EXPORT_SYMBOL_GPL(kvm_write_guest_cached);
 
-int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
-                          void *data, unsigned long len)
+int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+                                void *data, unsigned int offset,
+                                unsigned long len)
 {
        struct kvm_memslots *slots = kvm_memslots(kvm);
        int r;
+       gpa_t gpa = ghc->gpa + offset;
 
-       BUG_ON(len > ghc->len);
+       BUG_ON(len + offset > ghc->len);
 
        if (slots->generation != ghc->generation) {
                if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
@@ -2527,14 +2529,21 @@ int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                return -EFAULT;
 
        if (unlikely(!ghc->memslot))
-               return kvm_read_guest(kvm, ghc->gpa, data, len);
+               return kvm_read_guest(kvm, gpa, data, len);
 
-       r = __copy_from_user(data, (void __user *)ghc->hva, len);
+       r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);
        if (r)
                return -EFAULT;
 
        return 0;
 }
+EXPORT_SYMBOL_GPL(kvm_read_guest_offset_cached);
+
+int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+                         void *data, unsigned long len)
+{
+       return kvm_read_guest_offset_cached(kvm, ghc, data, 0, len);
+}
 EXPORT_SYMBOL_GPL(kvm_read_guest_cached);
 
 int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)