uio_hv_generic: Enable interrupt for low speed VMBus devices

Hyper-V is adding some "specialty" synthetic devices. Instead of writing
new kernel-level VMBus drivers for these devices, the devices will be
presented to user space via this existing Hyper-V generic UIO driver, so
that a user space driver can handle the device. Since these new synthetic
devices are low speed devices, they don't support monitor bits and we must
use vmbus_setevent() to enable interrupts from the host.

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Long Li <longli@microsoft.com>
Link: https://lore.kernel.org/r/1711788723-8593-4-git-send-email-ssengar@linux.microsoft.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 4bda6b52e49ea28b57efed9e785fa7228dd528f6..289611c7dfd79d0b8724ceab8c908eafb9f499f7 100644 (file)
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -84,6 +84,9 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
        dev->channel->inbound.ring_buffer->interrupt_mask = !irq_state;
        virt_mb();
 
+       if (!dev->channel->offermsg.monitor_allocated && irq_state)
+               vmbus_setevent(dev->channel);
+
        return 0;
 }
 
@@ -240,12 +243,6 @@ hv_uio_probe(struct hv_device *dev,
        int ret;
        size_t ring_size = hv_dev_ring_size(channel);
 
-       /* Communicating with host has to be via shared memory not hypercall */
-       if (!channel->offermsg.monitor_allocated) {
-               dev_err(&dev->device, "vmbus channel requires hypercall\n");
-               return -ENOTSUPP;
-       }
-
        if (!ring_size)
                ring_size = HV_RING_SIZE * PAGE_SIZE;