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>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index df85f5f..cba0b87 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2436,7 +2436,7 @@
unsigned int ioctl, unsigned long arg)
{
void __user *argp = (void __user *)arg;
- int r = -EINVAL;
+ long r = -EINVAL;
switch (ioctl) {
case KVM_GET_API_VERSION:
@@ -2478,6 +2478,12 @@
*/
r = 0;
break;
+ case KVM_GET_VCPU_MMAP_SIZE:
+ r = -EINVAL;
+ if (arg)
+ goto out;
+ r = PAGE_SIZE;
+ break;
default:
;
}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index c0d10cd..dad9081 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -253,6 +253,10 @@
* 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