[patch 1/2] libkvm: add kvm_has_sync_mmu

[Marcelo Tosatti <mtosatti@redhat.com>]

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From: Anthony Liguori <aliguori@us.ibm.com>

This patch adds a kvm_has_sync_mmu routine to libkvm.  This allows
userspace to query the existence of mmu notifiers which is important for
ballooning since madvise() is not safe from userspace without it.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm-userspace.tip/libkvm/libkvm.c
===================================================================
--- kvm-userspace.tip.orig/libkvm/libkvm.c
+++ kvm-userspace.tip/libkvm/libkvm.c
@@ -1053,6 +1053,15 @@ int kvm_pit_in_kernel(kvm_context_t kvm)
 	return kvm->pit_in_kernel;
 }
 
+int kvm_has_sync_mmu(kvm_context_t kvm)
+{
+        int r = 0;
+#ifdef KVM_CAP_SYNC_MMU
+        r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_SYNC_MMU);
+#endif
+        return r;
+}
+
 int kvm_init_coalesced_mmio(kvm_context_t kvm)
 {
 	int r = 0;
Index: kvm-userspace.tip/libkvm/libkvm.h
===================================================================
--- kvm-userspace.tip.orig/libkvm/libkvm.h
+++ kvm-userspace.tip/libkvm/libkvm.h
@@ -528,6 +528,8 @@ int kvm_dirty_pages_log_reset(kvm_contex
  */
 int kvm_irqchip_in_kernel(kvm_context_t kvm);
 
+int kvm_has_sync_mmu(kvm_context_t kvm);
+
 #ifdef KVM_CAP_IRQCHIP
 /*!
  * \brief Dump in kernel IRQCHIP contents

--