Make virtio_mmio_soft_reset reset the virtio device, which is performed by
both the "soft" and the "hard" reset; and then call virtio_mmio_soft_reset
from virtio_mmio_reset to emphasize that the latter is a superset of the
former.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/virtio/virtio-mmio.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 6d81a26473..d240efef97 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -72,12 +72,12 @@ static void virtio_mmio_soft_reset(VirtIOMMIOProxy *proxy)
 {
     int i;
 
-    if (proxy->legacy) {
-        return;
-    }
+    virtio_bus_reset(&proxy->bus);
 
-    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
-        proxy->vqs[i].enabled = 0;
+    if (!proxy->legacy) {
+        for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+            proxy->vqs[i].enabled = 0;
+        }
     }
 }
 
@@ -376,7 +376,7 @@ static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
             return;
         }
         if (value == 0) {
-            virtio_bus_reset(&vdev->bus);
+            virtio_mmio_soft_reset(proxy);
         } else {
             virtio_queue_set_addr(vdev, vdev->queue_sel,
                                   value << proxy->guest_page_shift);
@@ -432,7 +432,6 @@ 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;
@@ -627,7 +626,8 @@ static void virtio_mmio_reset(DeviceState *d)
     VirtIOMMIOProxy *proxy = VIRTIO_MMIO(d);
     int i;
 
-    virtio_bus_reset(&proxy->bus);
+    virtio_mmio_soft_reset(proxy);
+
     proxy->host_features_sel = 0;
     proxy->guest_features_sel = 0;
     proxy->guest_page_shift = 0;
@@ -636,7 +636,6 @@ static void virtio_mmio_reset(DeviceState *d)
         proxy->guest_features[0] = proxy->guest_features[1] = 0;
 
         for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
-            proxy->vqs[i].enabled = 0;
             proxy->vqs[i].num = 0;
             proxy->vqs[i].desc[0] = proxy->vqs[i].desc[1] = 0;
             proxy->vqs[i].avail[0] = proxy->vqs[i].avail[1] = 0;
-- 
2.36.1

On Thu, Jun 09 2022, Paolo Bonzini <pbonzini@redhat.com> wrote:

> Make virtio_mmio_soft_reset reset the virtio device, which is performed by
> both the "soft" and the "hard" reset; and then call virtio_mmio_soft_reset
> from virtio_mmio_reset to emphasize that the latter is a superset of the
> former.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/virtio/virtio-mmio.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index 6d81a26473..d240efef97 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -72,12 +72,12 @@ static void virtio_mmio_soft_reset(VirtIOMMIOProxy *proxy)
>  {
>      int i;
>  
> -    if (proxy->legacy) {
> -        return;
> -    }
> +    virtio_bus_reset(&proxy->bus);
>  
> -    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> -        proxy->vqs[i].enabled = 0;
> +    if (!proxy->legacy) {
> +        for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> +            proxy->vqs[i].enabled = 0;
> +        }
>      }
>  }

The more I look at this, the more confused I get.

The current code calls soft_reset when the driver sets the status to 0,
after already having called virtio_reset(). But doesn't virtio_reset()
ultimately already trigger the virtio-mmio reset routine, which sets
enabled to 0 for all queues? Why do that again? (And why is soft_reset a
"soft reset"?)

Maybe I'm missing something obvious, or it is simply -ENOCOFFEE on my side.

>  
> @@ -376,7 +376,7 @@ static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
>              return;
>          }
>          if (value == 0) {
> -            virtio_bus_reset(&vdev->bus);
> +            virtio_mmio_soft_reset(proxy);
>          } else {
>              virtio_queue_set_addr(vdev, vdev->queue_sel,
>                                    value << proxy->guest_page_shift);
> @@ -432,7 +432,6 @@ 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;
> @@ -627,7 +626,8 @@ static void virtio_mmio_reset(DeviceState *d)
>      VirtIOMMIOProxy *proxy = VIRTIO_MMIO(d);
>      int i;
>  
> -    virtio_bus_reset(&proxy->bus);
> +    virtio_mmio_soft_reset(proxy);
> +
>      proxy->host_features_sel = 0;
>      proxy->guest_features_sel = 0;
>      proxy->guest_page_shift = 0;
> @@ -636,7 +636,6 @@ static void virtio_mmio_reset(DeviceState *d)
>          proxy->guest_features[0] = proxy->guest_features[1] = 0;
>  
>          for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> -            proxy->vqs[i].enabled = 0;
>              proxy->vqs[i].num = 0;
>              proxy->vqs[i].desc[0] = proxy->vqs[i].desc[1] = 0;
>              proxy->vqs[i].avail[0] = proxy->vqs[i].avail[1] = 0;

On 6/9/22 14:22, Cornelia Huck wrote:
>> -    if (proxy->legacy) {
>> -        return;
>> -    }
>> +    virtio_bus_reset(&proxy->bus);
>>   
>> -    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
>> -        proxy->vqs[i].enabled = 0;
>> +    if (!proxy->legacy) {
>> +        for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
>> +            proxy->vqs[i].enabled = 0;
>> +        }
>>       }
>>   }
>
> The more I look at this, the more confused I get.
> 
> The current code calls soft_reset when the driver sets the status to 0,
> after already having called virtio_reset().

Yes, that's before the patch.

> But doesn't virtio_reset() ultimately already trigger the virtio-mmio
> reset routine, which sets enabled to 0 for all queues? Why do that
> again? (And why is soft_reset a "soft reset"?)
No, it does not set enabled = 0 because "enabled" is specific to 
virtio-mmio (it is read by VIRTIO_MMIO_QUEUE_READY, which is only 
available in virtio-mmio 1.0 devices).  In fact it is stored in 
proxy->vqs[], while virtio_reset only resets fields in vdev->vq[].

k->reset() instead triggers the *device* reset routine (e.g. 
virtio_blk_reset).  So what makes it "soft" is that the various queue 
addresses remain there, and can be enabled just by writing 1 to 
VIRTIO_MMIO_QUEUE_READY for every queue.

Paolo