KVM: Don't require explicit indication of completion of mmio or pio

It is illegal not to return from a pio or mmio request without completing
it, as mmio or pio is an atomic operation.  Therefore, we can simplify
the userspace interface by avoiding the completion indication.

Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/kvm_main.c

@@ -1237,8 +1237,10 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 	kvm_arch_ops->decache_regs(vcpu);
 	kvm_arch_ops->set_rflags(vcpu, emulate_ctxt.eflags);
 
-	if (vcpu->mmio_is_write)
+	if (vcpu->mmio_is_write) {
+		vcpu->mmio_needed = 0;
 		return EMULATE_DO_MMIO;
+	}
 
 	return EMULATE_DONE;
 }
@@ -1692,8 +1694,6 @@ static int complete_pio(struct kvm_vcpu *vcpu)
 			vcpu->regs[VCPU_REGS_RSI] += delta;
 	}
 
-	vcpu->run->io_completed = 0;
-
 	kvm_arch_ops->decache_regs(vcpu);
 
 	io->count -= io->cur_count;
@@ -1800,25 +1800,25 @@ static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	/* re-sync apic's tpr */
 	vcpu->cr8 = kvm_run->cr8;
 
-	if (kvm_run->io_completed) {
-		if (vcpu->pio.cur_count) {
-			r = complete_pio(vcpu);
-			if (r)
-				goto out;
-		} else if (!vcpu->mmio_is_write) {
-			memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8);
-			vcpu->mmio_read_completed = 1;
-			vcpu->mmio_needed = 0;
-			r = emulate_instruction(vcpu, kvm_run,
-					    vcpu->mmio_fault_cr2, 0);
-			if (r == EMULATE_DO_MMIO) {
-				/*
-				 * Read-modify-write.  Back to userspace.
-				 */
-				kvm_run->exit_reason = KVM_EXIT_MMIO;
-				r = 0;
-				goto out;
-			}
+	if (vcpu->pio.cur_count) {
+		r = complete_pio(vcpu);
+		if (r)
+			goto out;
+	}
+
+	if (vcpu->mmio_needed) {
+		memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8);
+		vcpu->mmio_read_completed = 1;
+		vcpu->mmio_needed = 0;
+		r = emulate_instruction(vcpu, kvm_run,
+					vcpu->mmio_fault_cr2, 0);
+		if (r == EMULATE_DO_MMIO) {
+			/*
+			 * Read-modify-write.  Back to userspace.
+			 */
+			kvm_run->exit_reason = KVM_EXIT_MMIO;
+			r = 0;
+			goto out;
 		}
 	}
 

include/linux/kvm.h

@@ -11,7 +11,7 @@
 #include <asm/types.h>
 #include <linux/ioctl.h>
 
-#define KVM_API_VERSION 10
+#define KVM_API_VERSION 11
 
 /*
  * Architectural interrupt line count, and the size of the bitmap needed
@@ -58,9 +58,8 @@ enum kvm_exit_reason {
 /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
 struct kvm_run {
 	/* in */
-	__u32 io_completed; /* mmio/pio request completed */
 	__u8 request_interrupt_window;
-	__u8 padding1[3];
+	__u8 padding1[7];
 
 	/* out */
 	__u32 exit_reason;