i386: hvf: Reset IRQ inhibition after moving RIP

The sequence of instructions exposes an issue:
  sti
  hlt

Interrupts cannot be delivered to hvf after hlt instruction cpu because
HF_INHIBIT_IRQ_MASK is set just before hlt is handled and never reset
after moving instruction pointer beyond hlt.

So, after hvf_vcpu_exec() returns, CPU thread gets locked up forever in
qemu_wait_io_event() (cpu_thread_is_idle() evaluates inhibition
flag and considers the CPU idle if the flag is set).

Cc: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Message-Id: <20200328174411.51491-1-r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/hvf/vmx.h

@@ -167,6 +167,8 @@ static inline void macvm_set_cr4(hv_vcpuid_t vcpu, uint64_t cr4)
 
 static inline void macvm_set_rip(CPUState *cpu, uint64_t rip)
 {
+    X86CPU *x86_cpu = X86_CPU(cpu);
+    CPUX86State *env = &x86_cpu->env;
     uint64_t val;
 
     /* BUG, should take considering overlap.. */
@@ -176,6 +178,7 @@ static inline void macvm_set_rip(CPUState *cpu, uint64_t rip)
    val = rvmcs(cpu->hvf_fd, VMCS_GUEST_INTERRUPTIBILITY);
    if (val & (VMCS_INTERRUPTIBILITY_STI_BLOCKING |
                VMCS_INTERRUPTIBILITY_MOVSS_BLOCKING)) {
+        env->hflags &= ~HF_INHIBIT_IRQ_MASK;
         wvmcs(cpu->hvf_fd, VMCS_GUEST_INTERRUPTIBILITY,
                val & ~(VMCS_INTERRUPTIBILITY_STI_BLOCKING |
                VMCS_INTERRUPTIBILITY_MOVSS_BLOCKING));