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>

4 files changed, 53 insertions, 0 deletions

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index edcf8a2..f43e553 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -5493,6 +5493,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
         assert(run->msr.reason == KVM_MSR_EXIT_REASON_FILTER);
         ret = kvm_handle_wrmsr(cpu, run);
         break;
+#ifdef CONFIG_XEN_EMU
+    case KVM_EXIT_XEN:
+        ret = kvm_xen_handle_exit(cpu, &run->xen);
+        break;
+#endif
     default:
         fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
         ret = -1;
diff --git a/target/i386/kvm/trace-events b/target/i386/kvm/trace-events
index 7c369db..cd6f842 100644
--- a/target/i386/kvm/trace-events
+++ b/target/i386/kvm/trace-events
@@ -5,3 +5,6 @@ kvm_x86_fixup_msi_error(uint32_t gsi) "VT-d failed to remap interrupt for GSI %"
 kvm_x86_add_msi_route(int virq) "Adding route entry for virq %d"
 kvm_x86_remove_msi_route(int virq) "Removing route entry for virq %d"
 kvm_x86_update_msi_routes(int num) "Updated %d MSI routes"
+
+# xen-emu.c
+kvm_xen_hypercall(int cpu, uint8_t cpl, uint64_t input, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t ret) "xen_hypercall: cpu %d cpl %d input %" PRIu64 " a0 0x%" PRIx64 " a1 0x%" PRIx64 " a2 0x%" PRIx64" ret 0x%" PRIx64
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 4883b95..476f464 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;
+}
diff --git a/target/i386/kvm/xen-emu.h b/target/i386/kvm/xen-emu.h
index d62f1d8..21faf6b 100644
--- a/target/i386/kvm/xen-emu.h
+++ b/target/i386/kvm/xen-emu.h
@@ -25,5 +25,6 @@
 
 int kvm_xen_init(KVMState *s, uint32_t hypercall_msr);
 int kvm_xen_init_vcpu(CPUState *cs);
+int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit);
 
 #endif /* QEMU_I386_KVM_XEN_EMU_H */