[v3,3/9] kvmtool: sample CPU endianness on virtio-mmio device reset

Commit Message

Marc Zyngier April 24, 2014, 6:17 p.m. UTC

Save the CPU endianness when the device is reset. It is widely
assumed that the guest won't change its endianness after, or at
least not without reseting the device first.

A default implementation of the endianness sampling just returns
the default "host endianness" value so that unsuspecting architectures
are not affected.

Signed-off-by: Marc Zyngier <[e-mail]>
---
 tools/kvm/include/kvm/kvm-cpu.h | 1 +
 tools/kvm/include/kvm/virtio.h  | 1 +
 tools/kvm/kvm-cpu.c             | 6 ++++++
 tools/kvm/virtio/mmio.c         | 3 +++
 4 files changed, 11 insertions(+)

Patch

diff --git a/tools/kvm/include/kvm/kvm-cpu.h b/tools/kvm/include/kvm/kvm-cpu.h
index 0ece28c..aa0cb54 100644
--- a/tools/kvm/include/kvm/kvm-cpu.h
+++ b/tools/kvm/include/kvm/kvm-cpu.h
@@ -15,6 +15,7 @@  void kvm_cpu__run(struct kvm_cpu *vcpu);
 void kvm_cpu__reboot(struct kvm *kvm);
 int kvm_cpu__start(struct kvm_cpu *cpu);
 bool kvm_cpu__handle_exit(struct kvm_cpu *vcpu);
+int kvm_cpu__get_endianness(struct kvm_cpu *vcpu);
 
 int kvm_cpu__get_debug_fd(void);
 void kvm_cpu__set_debug_fd(int fd);
diff --git a/tools/kvm/include/kvm/virtio.h b/tools/kvm/include/kvm/virtio.h
index f6bddd9..1180a3e 100644
--- a/tools/kvm/include/kvm/virtio.h
+++ b/tools/kvm/include/kvm/virtio.h
@@ -132,6 +132,7 @@  struct virtio_device {
 	bool			use_vhost;
 	void			*virtio;
 	struct virtio_ops	*ops;
+	u16			endian;
 };
 
 struct virtio_ops {
diff --git a/tools/kvm/kvm-cpu.c b/tools/kvm/kvm-cpu.c
index 5c70b00..9575b32 100644
--- a/tools/kvm/kvm-cpu.c
+++ b/tools/kvm/kvm-cpu.c
@@ -3,6 +3,7 @@ 
 #include "kvm/symbol.h"
 #include "kvm/util.h"
 #include "kvm/kvm.h"
+#include "kvm/virtio.h"
 
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ -14,6 +15,11 @@ 
 
 extern __thread struct kvm_cpu *current_kvm_cpu;
 
+int __attribute__((weak)) kvm_cpu__get_endianness(struct kvm_cpu *vcpu)
+{
+	return VIRTIO_ENDIAN_HOST;
+}
+
 void kvm_cpu__enable_singlestep(struct kvm_cpu *vcpu)
 {
 	struct kvm_guest_debug debug = {
diff --git a/tools/kvm/virtio/mmio.c b/tools/kvm/virtio/mmio.c
index 9d385e2..3a2bd62 100644
--- a/tools/kvm/virtio/mmio.c
+++ b/tools/kvm/virtio/mmio.c
@@ -4,6 +4,7 @@ 
 #include "kvm/ioport.h"
 #include "kvm/virtio.h"
 #include "kvm/kvm.h"
+#include "kvm/kvm-cpu.h"
 #include "kvm/irq.h"
 #include "kvm/fdt.h"
 
@@ -159,6 +160,8 @@  static void virtio_mmio_config_out(struct kvm_cpu *vcpu,
 		break;
 	case VIRTIO_MMIO_STATUS:
 		vmmio->hdr.status = ioport__read32(data);
+		if (!vmmio->hdr.status) /* Sample endianness on reset */
+			vdev->endian = kvm_cpu__get_endianness(vcpu);
 		if (vdev->ops->notify_status)
 			vdev->ops->notify_status(kvm, vmmio->dev, vmmio->hdr.status);
 		break;