x86/hvm: Replace do_sched_op calls with their underlying logic

do_sched_op(SCHEDOP_yield) just calls vcpu_yield(). Remove the indirection
through the hypercall handler and use the function directly.

Export vcpu_block_enable_events() to perform the same for SCHEDOP_block.

Not a functional change.

Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>

xen/arch/x86/hvm/hvm.c

@@ -1736,7 +1736,7 @@ void hvm_hlt(unsigned int eflags)
     if ( unlikely(!(eflags & X86_EFLAGS_IF)) )
         return hvm_vcpu_down(curr);
 
-    do_sched_op(SCHEDOP_block, guest_handle_from_ptr(NULL, void));
+    vcpu_block_enable_events();
 
     TRACE(TRC_HVM_HLT, /* pending = */ vcpu_runnable(curr));
 }

xen/arch/x86/hvm/svm/svm.c

@@ -2159,7 +2159,7 @@ static void svm_vmexit_do_pause(struct cpu_user_regs *regs)
      * Do something useful, like reschedule the guest
      */
     perfc_incr(pauseloop_exits);
-    do_sched_op(SCHEDOP_yield, guest_handle_from_ptr(NULL, void));
+    vcpu_yield();
 }
 
 static void

xen/arch/x86/hvm/viridian/viridian.c

@@ -959,7 +959,7 @@ int viridian_hypercall(struct cpu_user_regs *regs)
         /*
          * See section 14.5.1 of the specification.
          */
-        do_sched_op(SCHEDOP_yield, guest_handle_from_ptr(NULL, void));
+        vcpu_yield();
         break;
 
     case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE:

xen/arch/x86/hvm/vmx/vmx.c

@@ -4768,7 +4768,7 @@ void asmlinkage vmx_vmexit_handler(struct cpu_user_regs *regs)
 
     case EXIT_REASON_PAUSE_INSTRUCTION:
         perfc_incr(pauseloop_exits);
-        do_sched_op(SCHEDOP_yield, guest_handle_from_ptr(NULL, void));
+        vcpu_yield();
         break;
 
     case EXIT_REASON_XSETBV:

xen/common/sched/core.c

@@ -1430,7 +1430,7 @@ void vcpu_block(void)
     }
 }
 
-static void vcpu_block_enable_events(void)
+void vcpu_block_enable_events(void)
 {
     local_event_delivery_enable();
     vcpu_block();

xen/include/xen/sched.h

@@ -1030,6 +1030,7 @@ static inline bool vcpu_cpu_dirty(const struct vcpu *v)
 }
 
 void vcpu_block(void);
+void vcpu_block_enable_events(void);
 void vcpu_unblock(struct vcpu *v);
 
 void vcpu_pause(struct vcpu *v);