kvm: Implement support interrupt injection

This patch implement support for injecting interrupts from the userspace
hypervisor to the guest.

Signed-off-by: Pekka Enberg <penberg@kernel.org>

Makefile

@@ -27,6 +27,8 @@ DEPS	:= $(patsubst %.o,%.d,$(OBJS))
 OBJS	+= bios.o
 OBJS	+= bios/bios.o
 
+LIBS	+= -lrt
+
 uname_M      := $(shell uname -m | sed -e s/i.86/i386/)
 ifeq ($(uname_M),i386)
 	DEFINES      += -DCONFIG_X86_32
@@ -60,7 +62,7 @@ all: $(PROGRAM)
 
 $(PROGRAM): $(DEPS) $(OBJS)
 	$(E) "  LINK    " $@
-	$(Q) $(CC) $(OBJS) -o $@
+	$(Q) $(CC) $(OBJS) $(LIBS) -o $@
 
 $(DEPS):
 

early_printk.c

@@ -65,6 +65,11 @@ static struct serial8250_device device = {
 	.iobase			= 0x3f8,	/* ttyS0 */
 };
 
+void serial8250__interrupt(struct kvm *self)
+{
+	/* TODO: inject 8250 interrupt for the guest */
+}
+
 static bool serial8250_out(struct kvm *self, uint16_t port, void *data, int size, uint32_t count)
 {
 	uint16_t offset = port - device.iobase;

include/kvm/early_printk.h

@@ -1,6 +1,9 @@
 #ifndef KVM__EARLY_PRINTK_H
 #define KVM__EARLY_PRINTK_H
 
+struct kvm;
+
 void early_printk__init(void);
+void serial8250__interrupt(struct kvm *self);
 
 #endif /* KVM__EARLY_PRINTK_H */

kvm.c

@@ -608,7 +608,10 @@ void kvm__setup_mem(struct kvm *self)
 
 void kvm__run(struct kvm *self)
 {
-	if (ioctl(self->vcpu_fd, KVM_RUN, 0) < 0)
+	int err;
+
+	err = ioctl(self->vcpu_fd, KVM_RUN, 0);
+	if (err && (errno != EINTR && errno != EAGAIN))
 		die_perror("KVM_RUN failed");
 }
 

main.c

@@ -12,6 +12,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <time.h>
 
 extern bool ioport_debug;
 
@@ -45,6 +46,47 @@ static bool option_matches(char *arg, const char *option)
 	return !strncmp(arg, option, strlen(option));
 }
 
+#define TIMER_INTERVAL_NS 1000000000
+
+static void alarm_handler(int sig)
+{
+}
+
+/*
+ * This function sets up a timer that's used to inject interrupts from the
+ * userspace hypervisor into the guest at periodical intervals. Please note
+ * that clock interrupt, for example, is not handled here.
+ */
+static void setup_timer(void)
+{
+	struct itimerspec its;
+	struct sigaction sa;
+	struct sigevent sev;
+	timer_t timerid;
+
+	sigfillset(&sa.sa_mask);
+	sa.sa_flags			= 0;
+	sa.sa_handler			= alarm_handler;
+
+	sigaction(SIGALRM, &sa, NULL);
+
+	memset(&sev, 0, sizeof(struct sigevent));
+	sev.sigev_value.sival_int	= 0;
+	sev.sigev_notify		= SIGEV_SIGNAL;
+	sev.sigev_signo			= SIGALRM;
+
+	its.it_value.tv_sec		= TIMER_INTERVAL_NS / 1000000000;
+	its.it_value.tv_nsec		= TIMER_INTERVAL_NS % 1000000000;
+	its.it_interval.tv_sec		= its.it_value.tv_sec;
+	its.it_interval.tv_nsec		= its.it_value.tv_nsec;
+	if (timer_create(CLOCK_MONOTONIC, &sev, &timerid) < 0)
+		die("timer_create()");
+
+	if (timer_settime(timerid, 0, &its, NULL) < 0)
+		die("timer_settime()");
+}
+
+
 int main(int argc, char *argv[])
 {
 	const char *kernel_filename = NULL;
@@ -131,6 +173,8 @@ int main(int argc, char *argv[])
 
 	blk_virtio__init(kvm);
 
+	setup_timer();
+
 	for (;;) {
 		kvm__run(kvm);
 
@@ -165,7 +209,10 @@ int main(int argc, char *argv[])
 			if (!ret)
 				goto exit_kvm;
 			break;
-
+		}
+		case KVM_EXIT_INTR: {
+			serial8250__interrupt(kvm);
+			break;
 		}
 		default:
 			goto exit_kvm;