[RFC PATCH v3 09/38] i386/xen: handle guest hypercalls

[David Woodhouse <dwmw2@infradead.org>]

From: Joao Martins <joao.m.martins@oracle.com>

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>
---
 target/i386/kvm/kvm.c        |  5 +++++
 target/i386/kvm/trace-events |  3 +++
 target/i386/kvm/xen-emu.c    | 39 ++++++++++++++++++++++++++++++++++++
 target/i386/kvm/xen-emu.h    |  1 +
 4 files changed, 48 insertions(+)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 5977edb1ca..c37e44d88f 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -5466,6 +5466,11 @@ 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 7c369db1e1..cd6f842b1f 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 8433c4d70f..668713d5af 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -10,9 +10,11 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/log.h"
 #include "sysemu/kvm_int.h"
 #include "kvm/kvm_i386.h"
 #include "xen-emu.h"
+#include "trace.h"
 
 int kvm_xen_init(KVMState *s, uint32_t hypercall_msr)
 {
@@ -48,3 +50,40 @@ int kvm_xen_init(KVMState *s, uint32_t hypercall_msr)
 
     return 0;
 }
+
+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[1]);
+    }
+
+    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 2101df0182..76a3de6c4d 100644
--- a/target/i386/kvm/xen-emu.h
+++ b/target/i386/kvm/xen-emu.h
@@ -24,5 +24,6 @@
 #define XEN_VERSION(maj, min) ((maj) << 16 | (min))
 
 int kvm_xen_init(KVMState *s, uint32_t hypercall_msr);
+int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit);
 
 #endif /* QEMU_I386_KVM_XEN_EMU_H */
-- 
2.35.3