kvm: Allow to set shadow MMU size

Introduce the KVM-specific machine option kvm_shadow_mem. It allows to
set a custom shadow MMU size for the virtual machine. This is useful for
stress testing e.g.

Only x86 supports this for now, but it is in principle a generic
concept for all targets with shadow MMUs.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index e41de394d..445c06082 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -646,7 +646,9 @@ static int kvm_get_supported_msrs(KVMState *s)
 
 int kvm_arch_init(KVMState *s)
 {
+    QemuOptsList *list = qemu_find_opts("machine");
     uint64_t identity_base = 0xfffbc000;
+    uint64_t shadow_mem;
     int ret;
     struct utsname utsname;
 
@@ -693,6 +695,17 @@ int kvm_arch_init(KVMState *s)
     }
     qemu_register_reset(kvm_unpoison_all, NULL);
 
+    if (!QTAILQ_EMPTY(&list->head)) {
+        shadow_mem = qemu_opt_get_size(QTAILQ_FIRST(&list->head),
+                                       "kvm_shadow_mem", -1);
+        if (shadow_mem != -1) {
+            shadow_mem /= 4096;
+            ret = kvm_vm_ioctl(s, KVM_SET_NR_MMU_PAGES, shadow_mem);
+            if (ret < 0) {
+                return ret;
+            }
+        }
+    }
     return 0;
 }