[v3] uio_hv_generic: Set event for all channels on the device

[Patch v3] uio_hv_generic: Set event for all channels on the device

Posted by longli@linuxonhyperv.com 11 months ago

From: Long Li <longli@microsoft.com>

Hyper-V may offer a non latency sensitive device with subchannels without
monitor bit enabled. The decision is entirely on the Hyper-V host not
configurable within guest.

When a device has subchannels, also signal events for the subchannel
if its monitor bit is disabled.

This patch also removes the memory barrier when monitor bit is enabled
as it is not necessary. The memory barrier is only needed between
setting up interrupt mask and calling vmbus_set_event() when monitor
bit is disabled.

Signed-off-by: Long Li <longli@microsoft.com>
---
Change log
v2: Use vmbus_set_event() to avoid additional check on monitored bit
    Lock vmbus_connection.channel_mutex when going through subchannels
v3: Add details in commit messsage on the memory barrier.

 drivers/uio/uio_hv_generic.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 3976360d0096..45be2f8baade 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -65,6 +65,16 @@ struct hv_uio_private_data {
 	char	send_name[32];
 };
 
+static void set_event(struct vmbus_channel *channel, s32 irq_state)
+{
+	channel->inbound.ring_buffer->interrupt_mask = !irq_state;
+	if (!channel->offermsg.monitor_allocated && irq_state) {
+		/* MB is needed for host to see the interrupt mask first */
+		virt_mb();
+		vmbus_set_event(channel);
+	}
+}
+
 /*
  * This is the irqcontrol callback to be registered to uio_info.
  * It can be used to disable/enable interrupt from user space processes.
@@ -79,12 +89,15 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
 {
 	struct hv_uio_private_data *pdata = info->priv;
 	struct hv_device *dev = pdata->device;
+	struct vmbus_channel *primary, *sc;
 
-	dev->channel->inbound.ring_buffer->interrupt_mask = !irq_state;
-	virt_mb();
+	primary = dev->channel;
+	set_event(primary, irq_state);
 
-	if (!dev->channel->offermsg.monitor_allocated && irq_state)
-		vmbus_setevent(dev->channel);
+	mutex_lock(&vmbus_connection.channel_mutex);
+	list_for_each_entry(sc, &primary->sc_list, sc_list)
+		set_event(sc, irq_state);
+	mutex_unlock(&vmbus_connection.channel_mutex);
 
 	return 0;
 }
@@ -95,12 +108,19 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
 static void hv_uio_channel_cb(void *context)
 {
 	struct vmbus_channel *chan = context;
-	struct hv_device *hv_dev = chan->device_obj;
-	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
+	struct hv_device *hv_dev;
+	struct hv_uio_private_data *pdata;
 
 	chan->inbound.ring_buffer->interrupt_mask = 1;
 	virt_mb();
 
+	/*
+	 * The callback may come from a subchannel, in which case look
+	 * for the hv device in the primary channel
+	 */
+	hv_dev = chan->primary_channel ?
+		 chan->primary_channel->device_obj : chan->device_obj;
+	pdata = hv_get_drvdata(hv_dev);
 	uio_event_notify(&pdata->info);
 }
 
-- 
2.34.1

Re: [Patch v3] uio_hv_generic: Set event for all channels on the device

Posted by Wei Liu 10 months, 2 weeks ago

On Mon, Mar 10, 2025 at 03:12:01PM -0700, longli@linuxonhyperv.com wrote:
> From: Long Li <longli@microsoft.com>
> 
> Hyper-V may offer a non latency sensitive device with subchannels without
> monitor bit enabled. The decision is entirely on the Hyper-V host not
> configurable within guest.
> 
> When a device has subchannels, also signal events for the subchannel
> if its monitor bit is disabled.
> 
> This patch also removes the memory barrier when monitor bit is enabled
> as it is not necessary. The memory barrier is only needed between
> setting up interrupt mask and calling vmbus_set_event() when monitor
> bit is disabled.
> 
> Signed-off-by: Long Li <longli@microsoft.com>

Greg, are you going to take this patch?

I can take it if you want.

Thanks,
Wei.

> ---
> Change log
> v2: Use vmbus_set_event() to avoid additional check on monitored bit
>     Lock vmbus_connection.channel_mutex when going through subchannels
> v3: Add details in commit messsage on the memory barrier.
> 
>  drivers/uio/uio_hv_generic.c | 32 ++++++++++++++++++++++++++------
>  1 file changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 3976360d0096..45be2f8baade 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -65,6 +65,16 @@ struct hv_uio_private_data {
>  	char	send_name[32];
>  };
>  
> +static void set_event(struct vmbus_channel *channel, s32 irq_state)
> +{
> +	channel->inbound.ring_buffer->interrupt_mask = !irq_state;
> +	if (!channel->offermsg.monitor_allocated && irq_state) {
> +		/* MB is needed for host to see the interrupt mask first */
> +		virt_mb();
> +		vmbus_set_event(channel);
> +	}
> +}
> +
>  /*
>   * This is the irqcontrol callback to be registered to uio_info.
>   * It can be used to disable/enable interrupt from user space processes.
> @@ -79,12 +89,15 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
>  {
>  	struct hv_uio_private_data *pdata = info->priv;
>  	struct hv_device *dev = pdata->device;
> +	struct vmbus_channel *primary, *sc;
>  
> -	dev->channel->inbound.ring_buffer->interrupt_mask = !irq_state;
> -	virt_mb();
> +	primary = dev->channel;
> +	set_event(primary, irq_state);
>  
> -	if (!dev->channel->offermsg.monitor_allocated && irq_state)
> -		vmbus_setevent(dev->channel);
> +	mutex_lock(&vmbus_connection.channel_mutex);
> +	list_for_each_entry(sc, &primary->sc_list, sc_list)
> +		set_event(sc, irq_state);
> +	mutex_unlock(&vmbus_connection.channel_mutex);
>  
>  	return 0;
>  }
> @@ -95,12 +108,19 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
>  static void hv_uio_channel_cb(void *context)
>  {
>  	struct vmbus_channel *chan = context;
> -	struct hv_device *hv_dev = chan->device_obj;
> -	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
> +	struct hv_device *hv_dev;
> +	struct hv_uio_private_data *pdata;
>  
>  	chan->inbound.ring_buffer->interrupt_mask = 1;
>  	virt_mb();
>  
> +	/*
> +	 * The callback may come from a subchannel, in which case look
> +	 * for the hv device in the primary channel
> +	 */
> +	hv_dev = chan->primary_channel ?
> +		 chan->primary_channel->device_obj : chan->device_obj;
> +	pdata = hv_get_drvdata(hv_dev);
>  	uio_event_notify(&pdata->info);
>  }
>  
> -- 
> 2.34.1
>

Re: [Patch v3] uio_hv_generic: Set event for all channels on the device

Posted by Greg Kroah-Hartman 10 months, 2 weeks ago

On Tue, Mar 25, 2025 at 04:10:59PM +0000, Wei Liu wrote:
> On Mon, Mar 10, 2025 at 03:12:01PM -0700, longli@linuxonhyperv.com wrote:
> > From: Long Li <longli@microsoft.com>
> > 
> > Hyper-V may offer a non latency sensitive device with subchannels without
> > monitor bit enabled. The decision is entirely on the Hyper-V host not
> > configurable within guest.
> > 
> > When a device has subchannels, also signal events for the subchannel
> > if its monitor bit is disabled.
> > 
> > This patch also removes the memory barrier when monitor bit is enabled
> > as it is not necessary. The memory barrier is only needed between
> > setting up interrupt mask and calling vmbus_set_event() when monitor
> > bit is disabled.
> > 
> > Signed-off-by: Long Li <longli@microsoft.com>
> 
> Greg, are you going to take this patch?
> 
> I can take it if you want.

It's the merge window right now, neither of us should be taking it.  Let
me look into it after -rc1 is out.

thanks,

greg k-h

Re: [Patch v3] uio_hv_generic: Set event for all channels on the device

Posted by Wei Liu 10 months, 2 weeks ago

On Tue, Mar 25, 2025 at 12:39:54PM -0400, Greg Kroah-Hartman wrote:
> On Tue, Mar 25, 2025 at 04:10:59PM +0000, Wei Liu wrote:
> > On Mon, Mar 10, 2025 at 03:12:01PM -0700, longli@linuxonhyperv.com wrote:
> > > From: Long Li <longli@microsoft.com>
> > > 
> > > Hyper-V may offer a non latency sensitive device with subchannels without
> > > monitor bit enabled. The decision is entirely on the Hyper-V host not
> > > configurable within guest.
> > > 
> > > When a device has subchannels, also signal events for the subchannel
> > > if its monitor bit is disabled.
> > > 
> > > This patch also removes the memory barrier when monitor bit is enabled
> > > as it is not necessary. The memory barrier is only needed between
> > > setting up interrupt mask and calling vmbus_set_event() when monitor
> > > bit is disabled.
> > > 
> > > Signed-off-by: Long Li <longli@microsoft.com>
> > 
> > Greg, are you going to take this patch?
> > 
> > I can take it if you want.
> 
> It's the merge window right now, neither of us should be taking it.  Let
> me look into it after -rc1 is out.

Understood. Thank you for your response.

> 
> thanks,
> 
> greg k-h

Re: [Patch v3] uio_hv_generic: Set event for all channels on the device

Posted by Saurabh Singh Sengar 11 months ago

On Mon, Mar 10, 2025 at 03:12:01PM -0700, longli@linuxonhyperv.com wrote:
> From: Long Li <longli@microsoft.com>
> 
> Hyper-V may offer a non latency sensitive device with subchannels without
> monitor bit enabled. The decision is entirely on the Hyper-V host not
> configurable within guest.
> 
> When a device has subchannels, also signal events for the subchannel
> if its monitor bit is disabled.
> 
> This patch also removes the memory barrier when monitor bit is enabled
> as it is not necessary. The memory barrier is only needed between
> setting up interrupt mask and calling vmbus_set_event() when monitor
> bit is disabled.
> 
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
> Change log
> v2: Use vmbus_set_event() to avoid additional check on monitored bit
>     Lock vmbus_connection.channel_mutex when going through subchannels
> v3: Add details in commit messsage on the memory barrier.
> 
>  drivers/uio/uio_hv_generic.c | 32 ++++++++++++++++++++++++++------
>  1 file changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 3976360d0096..45be2f8baade 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -65,6 +65,16 @@ struct hv_uio_private_data {
>  	char	send_name[32];
>  };
>  
> +static void set_event(struct vmbus_channel *channel, s32 irq_state)
> +{
> +	channel->inbound.ring_buffer->interrupt_mask = !irq_state;
> +	if (!channel->offermsg.monitor_allocated && irq_state) {
> +		/* MB is needed for host to see the interrupt mask first */
> +		virt_mb();
> +		vmbus_set_event(channel);
> +	}
> +}
> +
>  /*
>   * This is the irqcontrol callback to be registered to uio_info.
>   * It can be used to disable/enable interrupt from user space processes.
> @@ -79,12 +89,15 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
>  {
>  	struct hv_uio_private_data *pdata = info->priv;
>  	struct hv_device *dev = pdata->device;
> +	struct vmbus_channel *primary, *sc;
>  
> -	dev->channel->inbound.ring_buffer->interrupt_mask = !irq_state;
> -	virt_mb();
> +	primary = dev->channel;
> +	set_event(primary, irq_state);
>  
> -	if (!dev->channel->offermsg.monitor_allocated && irq_state)
> -		vmbus_setevent(dev->channel);
> +	mutex_lock(&vmbus_connection.channel_mutex);
> +	list_for_each_entry(sc, &primary->sc_list, sc_list)
> +		set_event(sc, irq_state);
> +	mutex_unlock(&vmbus_connection.channel_mutex);
>  
>  	return 0;
>  }
> @@ -95,12 +108,19 @@ hv_uio_irqcontrol(struct uio_info *info, s32 irq_state)
>  static void hv_uio_channel_cb(void *context)
>  {
>  	struct vmbus_channel *chan = context;
> -	struct hv_device *hv_dev = chan->device_obj;
> -	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
> +	struct hv_device *hv_dev;
> +	struct hv_uio_private_data *pdata;
>  
>  	chan->inbound.ring_buffer->interrupt_mask = 1;
>  	virt_mb();
>  
> +	/*
> +	 * The callback may come from a subchannel, in which case look
> +	 * for the hv device in the primary channel
> +	 */
> +	hv_dev = chan->primary_channel ?
> +		 chan->primary_channel->device_obj : chan->device_obj;
> +	pdata = hv_get_drvdata(hv_dev);
>  	uio_event_notify(&pdata->info);
>  }
>  
> -- 
> 2.34.1
> 

Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>

- Saurabh