diff mbox series

virtio-mmio: Clear v2 transport state on soft reset

Message ID 20191213095410.1516119-1-jean-philippe@linaro.org
State Superseded
Headers show
Series virtio-mmio: Clear v2 transport state on soft reset | expand

Commit Message

Jean-Philippe Brucker Dec. 13, 2019, 9:54 a.m. UTC
At the moment when the guest writes a status of 0, we only reset the
virtio core state but not the virtio-mmio state. The virtio-mmio
specification says (v1.1 cs01, 4.2.2.1 Device Requirements:
MMIO Device Register Layout):

    Upon reset, the device MUST clear all bits in InterruptStatus and
    ready bits in the QueueReady register for all queues in the device.

The core already takes care of InterruptStatus by clearing isr, but we
still need to clear QueueReady.

It would be tempting to clean all registers, but since the specification
doesn't say anything more, guests could rely on the registers keeping
their state across reset. Linux for example, relies on this for
GuestPageSize in the legacy MMIO tranport.

Fixes: 44e687a4d9ab ("virtio-mmio: implement modern (v2) personality (virtio-1)")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

---
This fixes kexec of a Linux guest that uses the modern virtio-mmio
transport.
---
 hw/virtio/virtio-mmio.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

-- 
2.24.0

Comments

Sergio Lopez Dec. 13, 2019, 10:26 a.m. UTC | #1
Jean-Philippe Brucker <jean-philippe@linaro.org> writes:

> At the moment when the guest writes a status of 0, we only reset the

> virtio core state but not the virtio-mmio state. The virtio-mmio

> specification says (v1.1 cs01, 4.2.2.1 Device Requirements:

> MMIO Device Register Layout):

>

>     Upon reset, the device MUST clear all bits in InterruptStatus and

>     ready bits in the QueueReady register for all queues in the device.

>

> The core already takes care of InterruptStatus by clearing isr, but we

> still need to clear QueueReady.

>

> It would be tempting to clean all registers, but since the specification

> doesn't say anything more, guests could rely on the registers keeping

> their state across reset. Linux for example, relies on this for

> GuestPageSize in the legacy MMIO tranport.

>

> Fixes: 44e687a4d9ab ("virtio-mmio: implement modern (v2) personality (virtio-1)")

> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---

> This fixes kexec of a Linux guest that uses the modern virtio-mmio

> transport.

> ---

>  hw/virtio/virtio-mmio.c | 14 ++++++++++++++

>  1 file changed, 14 insertions(+)


LGTM, thanks!

Reviewed-by: Sergio Lopez <slp@redhat.com>
diff mbox series

Patch

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 94d934c44b..ef40b7a9b2 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -65,6 +65,19 @@  static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
     virtio_bus_stop_ioeventfd(&proxy->bus);
 }
 
+static void virtio_mmio_soft_reset(VirtIOMMIOProxy *proxy)
+{
+    int i;
+
+    if (proxy->legacy) {
+        return;
+    }
+
+    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+        proxy->vqs[i].enabled = 0;
+    }
+}
+
 static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
 {
     VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
@@ -378,6 +391,7 @@  static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
 
         if (vdev->status == 0) {
             virtio_reset(vdev);
+            virtio_mmio_soft_reset(proxy);
         }
         break;
     case VIRTIO_MMIO_QUEUE_DESC_LOW: