i386/xen: handle guest hypercalls

This means handling the new exit reason for Xen but still
crashing on purpose. As we implement each of the hypercalls
we will then return the right return code.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
[dwmw2: Add CPL to hypercall tracing, disallow hypercalls from CPL > 0]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 4883b95d9d..476f464ee2 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -10,10 +10,12 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/log.h"
 #include "sysemu/kvm_int.h"
 #include "sysemu/kvm_xen.h"
 #include "kvm/kvm_i386.h"
 #include "xen-emu.h"
+#include "trace.h"
 
 int kvm_xen_init(KVMState *s, uint32_t hypercall_msr)
 {
@@ -84,3 +86,45 @@ uint32_t kvm_xen_get_caps(void)
 {
     return kvm_state->xen_caps;
 }
+
+static bool do_kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit)
+{
+    uint16_t code = exit->u.hcall.input;
+
+    if (exit->u.hcall.cpl > 0) {
+        exit->u.hcall.result = -EPERM;
+        return true;
+    }
+
+    switch (code) {
+    default:
+        return false;
+    }
+}
+
+int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit)
+{
+    if (exit->type != KVM_EXIT_XEN_HCALL) {
+        return -1;
+    }
+
+    if (!do_kvm_xen_handle_exit(cpu, exit)) {
+        /*
+         * Some hypercalls will be deliberately "implemented" by returning
+         * -ENOSYS. This case is for hypercalls which are unexpected.
+         */
+        exit->u.hcall.result = -ENOSYS;
+        qemu_log_mask(LOG_UNIMP, "Unimplemented Xen hypercall %"
+                      PRId64 " (0x%" PRIx64 " 0x%" PRIx64 " 0x%" PRIx64 ")\n",
+                      (uint64_t)exit->u.hcall.input,
+                      (uint64_t)exit->u.hcall.params[0],
+                      (uint64_t)exit->u.hcall.params[1],
+                      (uint64_t)exit->u.hcall.params[2]);
+    }
+
+    trace_kvm_xen_hypercall(CPU(cpu)->cpu_index, exit->u.hcall.cpl,
+                            exit->u.hcall.input, exit->u.hcall.params[0],
+                            exit->u.hcall.params[1], exit->u.hcall.params[2],
+                            exit->u.hcall.result);
+    return 0;
+}