On Wed, Mar 13, 2024 at 10:40:21AM +0100, Markus Armbruster wrote:
> I could be awkward for the use case described in PATCH 1's commit
> message:
>
> However, we sometimes want to compare features and status bits without
> caring for their exact meaning. Say we want to verify the correctness
> of the virtio negotiation between guest, QEMU, and OVS-DPDK. We can use
> QMP command x-query-virtio-status to retrieve vhost-user net device
> features, and the "ovs-vsctl list interface" command to retrieve
> interface features. Without commit f3034ad71fc, we could then simply
> compare the numbers. With this commit, we first have to map from the
> strings back to the numeric encoding.
So, consider how guest kernel presents features then. Do you happen to know?
It's actually a binary string:
static ssize_t features_show(struct device *_d,
struct device_attribute *attr, char *buf)
{
struct virtio_device *dev = dev_to_virtio(_d);
unsigned int i;
ssize_t len = 0;
/* We actually represent this as a bitstring, as it could be
* arbitrary length in future. */
for (i = 0; i < sizeof(dev->features)*8; i++)
len += sysfs_emit_at(buf, len, "%c",
__virtio_test_bit(dev, i) ? '1' : '0');
len += sysfs_emit_at(buf, len, "\n");
return len;
}
static DEVICE_ATTR_RO(features);
--
MST
