KVM: Rework VCPU state writeback API
This grand cleanup drops all reset and vmsave/load related
synchronization points in favor of four(!) generic hooks:
- cpu_synchronize_all_states in qemu_savevm_state_complete
(initial sync from kernel before vmsave)
- cpu_synchronize_all_post_init in qemu_loadvm_state
(writeback after vmload)
- cpu_synchronize_all_post_init in main after machine init
- cpu_synchronize_all_post_reset in qemu_system_reset
(writeback after system reset)
These writeback points + the existing one of VCPU exec after
cpu_synchronize_state map on three levels of writeback:
- KVM_PUT_RUNTIME_STATE (during runtime, other VCPUs continue to run)
- KVM_PUT_RESET_STATE (on synchronous system reset, all VCPUs stopped)
- KVM_PUT_FULL_STATE (on init or vmload, all VCPUs stopped as well)
This level is passed to the arch-specific VCPU state writing function
that will decide which concrete substates need to be written. That way,
no writer of load, save or reset functions that interact with in-kernel
KVM states will ever have to worry about synchronization again. That
also means that a lot of reasons for races, segfaults and deadlocks are
eliminated.
cpu_synchronize_state remains untouched, just as Anthony suggested. We
continue to need it before reading or writing of VCPU states that are
also tracked by in-kernel KVM subsystems.
Consequently, this patch removes many cpu_synchronize_state calls that
are now redundant, just like remaining explicit register syncs.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/vl.c b/vl.c
index 274d847..10d8e34 100644
--- a/vl.c
+++ b/vl.c
@@ -3002,6 +3002,33 @@
qemu_mod_timer(nographic_timer, interval + qemu_get_clock(rt_clock));
}
+void cpu_synchronize_all_states(void)
+{
+ CPUState *cpu;
+
+ for (cpu = first_cpu; cpu; cpu = cpu->next_cpu) {
+ cpu_synchronize_state(cpu);
+ }
+}
+
+void cpu_synchronize_all_post_reset(void)
+{
+ CPUState *cpu;
+
+ for (cpu = first_cpu; cpu; cpu = cpu->next_cpu) {
+ cpu_synchronize_post_reset(cpu);
+ }
+}
+
+void cpu_synchronize_all_post_init(void)
+{
+ CPUState *cpu;
+
+ for (cpu = first_cpu; cpu; cpu = cpu->next_cpu) {
+ cpu_synchronize_post_init(cpu);
+ }
+}
+
struct vm_change_state_entry {
VMChangeStateHandler *cb;
void *opaque;
@@ -3143,6 +3170,7 @@
QTAILQ_FOREACH_SAFE(re, &reset_handlers, entry, nre) {
re->func(re->opaque);
}
+ cpu_synchronize_all_post_reset();
}
void qemu_system_reset_request(void)
@@ -5928,6 +5956,7 @@
machine->init(ram_size, boot_devices,
kernel_filename, kernel_cmdline, initrd_filename, cpu_model);
+ cpu_synchronize_all_post_init();
#ifndef _WIN32
/* must be after terminal init, SDL library changes signal handlers */