[RFC PATCH v4 12/47] i386/xen: implement HYPERVISOR_sched_op, SCHEDOP_shutdown

[David Woodhouse]

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

It allows to shutdown itself via hypercall with any of the 3 reasons:
  1) self-reboot
  2) shutdown
  3) crash

Implementing SCHEDOP_shutdown sub op let us handle crashes gracefully rather
than leading to triple faults if it remains unimplemented.

In addition, the SHUTDOWN_soft_reset reason is used for kexec, to reset
Xen shared pages and other enlightenments and leave a clean slate for the
new kernel without the hypervisor helpfully writing information at
unexpected addresses.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
[dwmw2: Ditch sched_op_compat which was never available for HVM guests,
        Add SCHEDOP_soft_reset]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 target/i386/kvm/xen-emu.c | 68 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 1dea6feb90..5f2b55ef10 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -17,8 +17,10 @@
 #include "exec/address-spaces.h"
 #include "xen-emu.h"
 #include "trace.h"
+#include "sysemu/runstate.h"
 
 #include "standard-headers/xen/version.h"
+#include "standard-headers/xen/sched.h"
 
 static int kvm_gva_rw(CPUState *cs, uint64_t gva, void *_buf, size_t sz,
                       bool is_write)
@@ -170,6 +172,69 @@ static bool kvm_xen_hcall_xen_version(struct kvm_xen_exit 
*exit, X86CPU *cpu,
     return true;
 }
 
+static int kvm_xen_soft_reset(void)
+{
+    /* Nothing to reset... yet. */
+    return 0;
+}
+
+static int schedop_shutdown(CPUState *cs, uint64_t arg)
+{
+    struct sched_shutdown shutdown;
+    int ret = 0;
+
+    /* No need for 32/64 compat handling */
+    qemu_build_assert(sizeof(shutdown) == 4);
+
+    if (kvm_copy_from_gva(cs, arg, &shutdown, sizeof(shutdown))) {
+        return -EFAULT;
+    }
+
+    switch (shutdown.reason) {
+    case SHUTDOWN_crash:
+        cpu_dump_state(cs, stderr, CPU_DUMP_CODE);
+        qemu_system_guest_panicked(NULL);
+        break;
+
+    case SHUTDOWN_reboot:
+        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
+        break;
+
+    case SHUTDOWN_poweroff:
+        qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
+        break;
+
+    case SHUTDOWN_soft_reset:
+        ret = kvm_xen_soft_reset();
+        break;
+
+    default:
+        ret = -EINVAL;
+        break;
+    }
+
+    return ret;
+}
+
+static bool kvm_xen_hcall_sched_op(struct kvm_xen_exit *exit, X86CPU *cpu,
+                                   int cmd, uint64_t arg)
+{
+    CPUState *cs = CPU(cpu);
+    int err = -ENOSYS;
+
+    switch (cmd) {
+    case SCHEDOP_shutdown:
+        err = schedop_shutdown(cs, arg);
+        break;
+
+    default:
+        return false;
+    }
+
+    exit->u.hcall.result = err;
+    return true;
+}
+
 static bool do_kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit)
 {
     uint16_t code = exit->u.hcall.input;
@@ -180,6 +245,9 @@ static bool do_kvm_xen_handle_exit(X86CPU *cpu, struct 
kvm_xen_exit *exit)
     }
 
     switch (code) {
+    case __HYPERVISOR_sched_op:
+        return kvm_xen_hcall_sched_op(exit, cpu, exit->u.hcall.params[0],
+                                      exit->u.hcall.params[1]);
     case __HYPERVISOR_xen_version:
         return kvm_xen_hcall_xen_version(exit, cpu, exit->u.hcall.params[0],
                                          exit->u.hcall.params[1]);
-- 
2.35.3