KVM: Implement kvm_put_guest()

kvm_put_guest() is analogous to put_user() - it writes a single value to
the guest physical address. The implementation is built upon put_user()
and so it has the same single copy atomic properties.

Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 719fc3e..9907e45 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -746,6 +746,28 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                                  unsigned long len);
 int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                              gpa_t gpa, unsigned long len);
+
+#define __kvm_put_guest(kvm, gfn, offset, value, type)                 \
+({                                                                     \
+       unsigned long __addr = gfn_to_hva(kvm, gfn);                    \
+       type __user *__uaddr = (type __user *)(__addr + offset);        \
+       int __ret = -EFAULT;                                            \
+                                                                       \
+       if (!kvm_is_error_hva(__addr))                                  \
+               __ret = put_user(value, __uaddr);                       \
+       if (!__ret)                                                     \
+               mark_page_dirty(kvm, gfn);                              \
+       __ret;                                                          \
+})
+
+#define kvm_put_guest(kvm, gpa, value, type)                           \
+({                                                                     \
+       gpa_t __gpa = gpa;                                              \
+       struct kvm *__kvm = kvm;                                        \
+       __kvm_put_guest(__kvm, __gpa >> PAGE_SHIFT,                     \
+                       offset_in_page(__gpa), (value), type);          \
+})
+
 int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
 int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);