linux-kernel - RE: [PATCH 3/6] uio_hv_generic: Enable interrupt for low speed VMBus devices

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Date: Tue, 12 Mar 2024 20:59:49 +0000
From: Long Li <longli@...rosoft.com>
To: Saurabh Sengar <ssengar@...ux.microsoft.com>, KY Srinivasan
	<kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>,
	"wei.liu@...nel.org" <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Saurabh Singh Sengar <ssengar@...rosoft.com>
Subject: RE: [PATCH 3/6] uio_hv_generic: Enable interrupt for low speed VMBus
 devices

> Subject: [PATCH 3/6] 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@...ux.microsoft.com>

Reviewed-by: Long Li <longli@...rosoft.com>

> ---
>  drivers/uio/uio_hv_generic.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c index
> 4bda6b52e49e..289611c7dfd7 100644
> --- 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;
> 
> --
> 2.34.1
>