x86/kvm: Use generic xfer to guest work function

Use the generic infrastructure to check for and handle pending work before
transitioning into guest mode.

This now handles TIF_NOTIFY_RESUME as well which was ignored so
far. Handling it is important as this covers task work and task work will
be used to offload the heavy lifting of POSIX CPU timers to thread context.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200722220520.979724969@linutronix.de

arch/x86/kvm/Kconfig

@@ -42,6 +42,7 @@ config KVM
 	select HAVE_KVM_MSI
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
 	select HAVE_KVM_NO_POLL
+	select KVM_XFER_TO_GUEST_WORK
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_VFIO
 	select SRCU

arch/x86/kvm/vmx/vmx.c

@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/tboot.h>
 #include <linux/trace_events.h>
+#include <linux/entry-kvm.h>
 
 #include <asm/apic.h>
 #include <asm/asm.h>
@@ -5373,14 +5374,12 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 		}
 
 		/*
-		 * Note, return 1 and not 0, vcpu_run() is responsible for
-		 * morphing the pending signal into the proper return code.
+		 * Note, return 1 and not 0, vcpu_run() will invoke
+		 * xfer_to_guest_mode() which will create a proper return
+		 * code.
 		 */
-		if (signal_pending(current))
+		if (__xfer_to_guest_mode_work_pending())
 			return 1;
-
-		if (need_resched())
-			schedule();
 	}
 
 	return 1;

arch/x86/kvm/x86.c

@@ -56,6 +56,7 @@
 #include <linux/sched/stat.h>
 #include <linux/sched/isolation.h>
 #include <linux/mem_encrypt.h>
+#include <linux/entry-kvm.h>
 
 #include <trace/events/kvm.h>
 
@@ -1587,7 +1588,7 @@ EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);
 bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu)
 {
 	return vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu) ||
-		need_resched() || signal_pending(current);
+		xfer_to_guest_mode_work_pending();
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_exit_request);
 
@@ -8681,15 +8682,11 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 			break;
 		}
 
-		if (signal_pending(current)) {
-			r = -EINTR;
-			vcpu->run->exit_reason = KVM_EXIT_INTR;
-			++vcpu->stat.signal_exits;
-			break;
-		}
-		if (need_resched()) {
+		if (xfer_to_guest_mode_work_pending()) {
 			srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
-			cond_resched();
+			r = xfer_to_guest_mode_handle_work(vcpu);
+			if (r)
+				return r;
 			vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
 		}
 	}