KVM: s390: Add MEMOP ioctls for reading/writing guest memory

On s390, we've got to make sure to hold the IPTE lock while accessing
logical memory. So let's add an ioctl for reading and writing logical
memory to provide this feature for userspace, too.
The maximum transfer size of this call is limited to 64kB to prevent
that the guest can trigger huge copy_from/to_user transfers. QEMU
currently only requests up to one or two pages so far, so 16*4kB seems
to be a reasonable limit here.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 82634a492fe0..0e16f2c9f0de 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -365,6 +365,24 @@ struct kvm_translation {
         __u8  pad[5];
 };
 
+/* for KVM_S390_MEM_OP */
+struct kvm_s390_mem_op {
+        /* in */
+        __u64 gaddr;            /* the guest address */
+        __u64 flags;            /* flags */
+        __u32 size;             /* amount of bytes */
+        __u32 op;               /* type of operation */
+        __u64 buf;              /* buffer in userspace */
+        __u8 ar;                /* the access register number */
+        __u8 reserved[31];      /* should be set to 0 */
+};
+/* types for kvm_s390_mem_op->op */
+#define KVM_S390_MEMOP_LOGICAL_READ     0
+#define KVM_S390_MEMOP_LOGICAL_WRITE    1
+/* flags for kvm_s390_mem_op->flags */
+#define KVM_S390_MEMOP_F_CHECK_ONLY             (1ULL << 0)
+#define KVM_S390_MEMOP_F_INJECT_EXCEPTION       (1ULL << 1)
+
 /* for KVM_INTERRUPT */
 struct kvm_interrupt {
         /* in */
@@ -761,6 +779,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_CHECK_EXTENSION_VM 105
 #define KVM_CAP_S390_USER_SIGP 106
 #define KVM_CAP_S390_VECTOR_REGISTERS 107
+#define KVM_CAP_S390_MEM_OP 108
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1136,6 +1155,8 @@ struct kvm_s390_ucas_mapping {
 #define KVM_ARM_VCPU_INIT         _IOW(KVMIO,  0xae, struct kvm_vcpu_init)
 #define KVM_ARM_PREFERRED_TARGET  _IOR(KVMIO,  0xaf, struct kvm_vcpu_init)
 #define KVM_GET_REG_LIST          _IOWR(KVMIO, 0xb0, struct kvm_reg_list)
+/* Available with KVM_CAP_S390_MEM_OP */
+#define KVM_S390_MEM_OP           _IOW(KVMIO,  0xb1, struct kvm_s390_mem_op)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU     (1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3          (1 << 1)