KVM: Allow kernel to select size of mmap() buffer

This allows us to store offsets in the kernel/user kvm_run area, and be
sure that userspace has them mapped.  As offsets can be outside the
kvm_run struct, userspace has no way of knowing how much to mmap.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index c0d10cd8088e..dad90816cad8 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -253,6 +253,10 @@ struct kvm_signal_mask {
  * return is 1 (yes) or 0 (no, sorry).
  */
 #define KVM_CHECK_EXTENSION       _IO(KVMIO,   0x03)
+/*
+ * Get size for mmap(vcpu_fd)
+ */
+#define KVM_GET_VCPU_MMAP_SIZE    _IO(KVMIO,   0x04) /* in bytes */
 
 /*
  * ioctls for VM fds