linux-kernel - Re: [PATCH v6] Drivers: hv: vmbus: Expose monitor data only when monitor pages are used

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Date:   Tue, 19 Mar 2019 10:26:09 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kimberly Brown <kimbrownkd@...il.com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        Long Li <longli@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] Drivers: hv: vmbus: Expose monitor data only when
 monitor pages are used

On Tue, Mar 19, 2019 at 12:04:01AM -0400, Kimberly Brown wrote:
> There are two methods for signaling the host: the monitor page mechanism
> and hypercalls. The monitor page mechanism is used by performance
> critical channels (storage, networking, etc.) because it provides
> improved throughput. However, latency is increased. Monitor pages are
> allocated to these channels.
> 
> Monitor pages are not allocated to channels that do not use the monitor
> page mechanism. Therefore, these channels do not have a valid monitor id
> or valid monitor page data. In these cases, some of the "_show"
> functions return incorrect data. They return an invalid monitor id and
> data that is beyond the bounds of the hv_monitor_page array fields.
> 
> The "channel->offermsg.monitor_allocated" value can be used to determine
> whether monitor pages have been allocated to a channel.
> 
> Add "is_visible()" callback functions for the device-level and
> channel-level attribute groups. These functions will hide the monitor
> sysfs files when the monitor mechanism is not used.
> 
> Remove ".default_attributes" from "vmbus_chan_attrs" and create a
> channel-level attribute group. These changes allow the new
> "is_visible()" callback function to be applied to the channel-level
> attributes.
> 
> Call "sysfs_create_group()" in "vmbus_add_channel_kobj()" to create the
> channel's sysfs files. Add a new function,
> “vmbus_remove_channel_attr_group()”, and call it in "free_channel()" to
> remove the channel's sysfs files when the channel is closed.
> 
> Signed-off-by: Kimberly Brown <kimbrownkd@...il.com>

Nice work, thanks for all of the changes you have made to this over
time.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>