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kvm-s390: implement config_changed for virtio on s390

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This patch implements config_changed for the s390 virtio transport.

We use the least significant bit of the interrupt parameter field
to decide, if this interrupt should call the virtio virtqueue callback
or the config_changed callback.

This method is compatible with old host and guest code. Old 64 bit guests
will not check the bit and trigger a harmless additional vring_interrupt
call. Old host code will never set this bit, this is also safe.

This patch also takes care of a potential future 31 bit virtio transport
for s390. On 31 bit _LC_PFAULT_INTPARM and __LC_EXT_PARAMS are identical.
We exploit the alignment of the token and fold the change bit into the
lsb of the token itself.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Christian Borntraeger 2008-11-18 22:44:13 +01:00 committed by Rusty Russell
parent c29834584e
commit be3c5832d5
1 changed files with 19 additions and 3 deletions
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22
drivers/s390/kvm/kvm_virtio.c
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@ -299,13 +299,29 @@ static void scan_devices(void)
*/
static void kvm_extint_handler(u16 code)
{
void *data = (void *) *(long *) __LC_PFAULT_INTPARM;
u16 subcode = S390_lowcore.cpu_addr;
struct virtqueue *vq;
u16 subcode;
int config_changed;
subcode = S390_lowcore.cpu_addr;
if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
return;
vring_interrupt(0, data);
/* The LSB might be overloaded, we have to mask it */
vq = (struct virtqueue *) ((*(long *) __LC_PFAULT_INTPARM) & ~1UL);
/* We use the LSB of extparam, to decide, if this interrupt is a config
* change or a "standard" interrupt */
config_changed = (*(int *) __LC_EXT_PARAMS & 1);
if (config_changed) {
struct virtio_driver *drv;
drv = container_of(vq->vdev->dev.driver,
struct virtio_driver, driver);
if (drv->config_changed)
drv->config_changed(vq->vdev);
} else
vring_interrupt(0, vq);
}
/*