KVM: s390: add parameter for KVM_CREATE_VM

This patch introduces a new config option for user controlled kernel
virtual machines. It introduces a parameter to KVM_CREATE_VM that
allows to set bits that alter the capabilities of the newly created
virtual machine.
The parameter is passed to kvm_arch_init_vm for all architectures.
The only valid modifier bit for now is KVM_VM_S390_UCONTROL.
This requires CAP_SYS_ADMIN privileges and creates a user controlled
virtual machine on s390 architectures.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

10 files changed, 65 insertions, 18 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e1d94bf4056e..579d40b26a5a 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -95,7 +95,7 @@ described as 'basic' will be available.
 Capability: basic
 Architectures: all
 Type: system ioctl
-Parameters: none
+Parameters: machine type identifier (KVM_VM_*)
 Returns: a VM fd that can be used to control the new virtual machine.
 
 The new VM has no virtual cpus and no memory.  An mmap() of a VM fd
@@ -103,6 +103,11 @@ will access the virtual machine's physical address space; offset zero
 corresponds to guest physical address zero.  Use of mmap() on a VM fd
 is discouraged if userspace memory allocation (KVM_CAP_USER_MEMORY) is
 available.
+You most certainly want to use 0 as machine type.
+
+In order to create user controlled virtual machines on S390, check
+KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
+privileged user (CAP_SYS_ADMIN).
 
 4.3 KVM_GET_MSR_INDEX_LIST
 
diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 405052002493..df6b14194051 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -809,10 +809,13 @@ static void kvm_build_io_pmt(struct kvm *kvm)
 #define GUEST_PHYSICAL_RR4      0x2739
 #define VMM_INIT_RR             0x1660
 
-int kvm_arch_init_vm(struct kvm *kvm)
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
         BUG_ON(!kvm);
 
+        if (type)
+                return -EINVAL;
+
         kvm->arch.is_sn2 = ia64_platform_is("sn2");
 
         kvm->arch.metaphysical_rr0 = GUEST_PHYSICAL_RR0;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 607fbdf24b84..83f244569874 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -171,8 +171,11 @@ void kvm_arch_check_processor_compat(void *rtn)
         *(int *)rtn = kvmppc_core_check_processor_compat();
 }
 
-int kvm_arch_init_vm(struct kvm *kvm)
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
+        if (type)
+                return -EINVAL;
+
         return kvmppc_core_init_vm(kvm);
 }
 
diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index a21634173a66..78eb9847008f 100644
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -34,6 +34,15 @@ config KVM
 
           If unsure, say N.
 
+config KVM_S390_UCONTROL
+        bool "Userspace controlled virtual machines"
+        depends on KVM
+        ---help---
+          Allow CAP_SYS_ADMIN users to create KVM virtual machines that are
+          controlled by userspace.
+
+          If unsure, say N.
+
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.
 source drivers/vhost/Kconfig
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index d1c445732451..f0937552175b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -171,11 +171,22 @@ long kvm_arch_vm_ioctl(struct file *filp,
         return r;
 }
 
-int kvm_arch_init_vm(struct kvm *kvm)
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
         int rc;
         char debug_name[16];
 
+        rc = -EINVAL;
+#ifdef CONFIG_KVM_S390_UCONTROL
+        if (type & ~KVM_VM_S390_UCONTROL)
+                goto out_err;
+        if ((type & KVM_VM_S390_UCONTROL) && (!capable(CAP_SYS_ADMIN)))
+                goto out_err;
+#else
+        if (type)
+                goto out_err;
+#endif
+
         rc = s390_enable_sie();
         if (rc)
                 goto out_err;
@@ -198,10 +209,13 @@ int kvm_arch_init_vm(struct kvm *kvm)
         debug_register_view(kvm->arch.dbf, &debug_sprintf_view);
         VM_EVENT(kvm, 3, "%s", "vm created");
 
-        kvm->arch.gmap = gmap_alloc(current->mm);
-        if (!kvm->arch.gmap)
-                goto out_nogmap;
-
+        if (type & KVM_VM_S390_UCONTROL) {
+                kvm->arch.gmap = NULL;
+        } else {
+                kvm->arch.gmap = gmap_alloc(current->mm);
+                if (!kvm->arch.gmap)
+                        goto out_nogmap;
+        }
         return 0;
 out_nogmap:
         debug_unregister(kvm->arch.dbf);
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 99b0b7597115..45b236a7c730 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -47,6 +47,16 @@ static inline int __cpu_is_stopped(struct kvm_vcpu *vcpu)
         return atomic_read(&vcpu->arch.sie_block->cpuflags) & CPUSTAT_STOP_INT;
 }
 
+static inline int kvm_is_ucontrol(struct kvm *kvm)
+{
+#ifdef CONFIG_KVM_S390_UCONTROL
+        if (kvm->arch.gmap)
+                return 0;
+        return 1;
+#else
+        return 0;
+#endif
+}
 int kvm_s390_handle_wait(struct kvm_vcpu *vcpu);
 enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer);
 void kvm_s390_tasklet(unsigned long parm);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9cbfc0698118..06925b4bcc27 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6031,8 +6031,11 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
         free_page((unsigned long)vcpu->arch.pio_data);
 }
 
-int kvm_arch_init_vm(struct kvm *kvm)
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
+        if (type)
+                return -EINVAL;
+
         INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
         INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
 
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 68e67e50d028..bba393a6760f 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -431,6 +431,9 @@ struct kvm_ppc_pvinfo {
 
 #define KVMIO 0xAE
 
+/* machine type bits, to be used as argument to KVM_CREATE_VM */
+#define KVM_VM_S390_UCONTROL    1
+
 /*
  * ioctls for /dev/kvm fds:
  */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 900c76337e8f..82375e145e64 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -520,7 +520,7 @@ static inline void kvm_arch_free_vm(struct kvm *kvm)
 }
 #endif
 
-int kvm_arch_init_vm(struct kvm *kvm);
+int kvm_arch_init_vm(struct kvm *kvm, unsigned long type);
 void kvm_arch_destroy_vm(struct kvm *kvm);
 void kvm_free_all_assigned_devices(struct kvm *kvm);
 void kvm_arch_sync_events(struct kvm *kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a91f980077d8..32e3b048a6cf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -449,7 +449,7 @@ static void kvm_init_memslots_id(struct kvm *kvm)
                 slots->id_to_index[i] = slots->memslots[i].id = i;
 }
 
-static struct kvm *kvm_create_vm(void)
+static struct kvm *kvm_create_vm(unsigned long type)
 {
         int r, i;
         struct kvm *kvm = kvm_arch_alloc_vm();
@@ -457,7 +457,7 @@ static struct kvm *kvm_create_vm(void)
         if (!kvm)
                 return ERR_PTR(-ENOMEM);
 
-        r = kvm_arch_init_vm(kvm);
+        r = kvm_arch_init_vm(kvm, type);
         if (r)
                 goto out_err_nodisable;
 
@@ -2198,12 +2198,12 @@ static struct file_operations kvm_vm_fops = {
         .llseek         = noop_llseek,
 };
 
-static int kvm_dev_ioctl_create_vm(void)
+static int kvm_dev_ioctl_create_vm(unsigned long type)
 {
         int r;
         struct kvm *kvm;
 
-        kvm = kvm_create_vm();
+        kvm = kvm_create_vm(type);
         if (IS_ERR(kvm))
                 return PTR_ERR(kvm);
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
@@ -2254,10 +2254,7 @@ static long kvm_dev_ioctl(struct file *filp,
                 r = KVM_API_VERSION;
                 break;
         case KVM_CREATE_VM:
-                r = -EINVAL;
-                if (arg)
-                        goto out;
-                r = kvm_dev_ioctl_create_vm();
+                r = kvm_dev_ioctl_create_vm(arg);
                 break;
         case KVM_CHECK_EXTENSION:
                 r = kvm_dev_ioctl_check_extension_generic(arg);