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. Move the device-level monitor page attributes to a separate attribute_group struct. If the channel uses the monitor page mechanism, set up the sysfs files for these attributes in vmbus_device_register(). Move the channel-level monitor page attributes to a separate attribute_group struct. If the channel uses the monitor page mechanism, set up the sysfs files for these attributes in vmbus_add_channel_kobj(). Signed-off-by: Kimberly Brown <[email protected]> --- Changes in v3: The monitor "_show" functions no longer return an error when a channel does not use the monitor page mechanism. Instead, the monitor page sysfs files are created only when a channel uses the monitor page mechanism. This change was suggested by G. Kroah-Hartman. Note: this patch was originally patch 2/2 in a patchset. Patch 1/2 has already been added to char-misc-testing, so I'm not resending it. Changes in v2: - Changed the return value for cases where monitor_allocated is not set to "-EINVAL". - Updated the commit message to provide more details about the monitor page mechanism. - Updated the sysfs documentation to describe the new return value. Documentation/ABI/stable/sysfs-bus-vmbus | 12 ++++-- drivers/hv/vmbus_drv.c | 52 +++++++++++++++++++----- 2 files changed, 51 insertions(+), 13 deletions(-) diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus b/Documentation/ABI/stable/sysfs-bus-vmbus index 826689dcc2e6..6d5cb195b119 100644 --- a/Documentation/ABI/stable/sysfs-bus-vmbus +++ b/Documentation/ABI/stable/sysfs-bus-vmbus @@ -81,7 +81,9 @@ What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/latency Date: September. 2017 KernelVersion: 4.14 Contact: Stephen Hemminger <[email protected]> -Description: Channel signaling latency +Description: Channel signaling latency. This file is available only for + performance critical channels (storage, network, etc.) that use + the monitor page mechanism. Users: Debugging tools What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/out_mask @@ -95,7 +97,9 @@ What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/pending Date: September. 2017 KernelVersion: 4.14 Contact: Stephen Hemminger <[email protected]> -Description: Channel interrupt pending state +Description: Channel interrupt pending state. This file is available only for + performance critical channels (storage, network, etc.) that use + the monitor page mechanism. Users: Debugging tools What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/read_avail @@ -137,7 +141,9 @@ What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/monitor_id Date: January. 2018 KernelVersion: 4.16 Contact: Stephen Hemminger <[email protected]> -Description: Monitor bit associated with channel +Description: Monitor bit associated with channel. This file is available only + for performance critical channels (storage, network, etc.) that + use the monitor page mechanism. Users: Debugging tools and userspace drivers What: /sys/bus/vmbus/devices/<UUID>/channels/<N>/ring diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 000b53e5a17a..ede858b0ee46 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -601,19 +601,12 @@ static DEVICE_ATTR_RW(driver_override); static struct attribute *vmbus_dev_attrs[] = { &dev_attr_id.attr, &dev_attr_state.attr, - &dev_attr_monitor_id.attr, &dev_attr_class_id.attr, &dev_attr_device_id.attr, &dev_attr_modalias.attr, #ifdef CONFIG_NUMA &dev_attr_numa_node.attr, #endif - &dev_attr_server_monitor_pending.attr, - &dev_attr_client_monitor_pending.attr, - &dev_attr_server_monitor_latency.attr, - &dev_attr_client_monitor_latency.attr, - &dev_attr_server_monitor_conn_id.attr, - &dev_attr_client_monitor_conn_id.attr, &dev_attr_out_intr_mask.attr, &dev_attr_out_read_index.attr, &dev_attr_out_write_index.attr, @@ -632,6 +625,22 @@ static struct attribute *vmbus_dev_attrs[] = { }; ATTRIBUTE_GROUPS(vmbus_dev); +/* + * Set up per device monitor page attributes. These attributes are used only by + * channels that use the monitor page mechanism. + */ +static struct attribute *vmbus_dev_monitor_attrs[] = { + &dev_attr_monitor_id.attr, + &dev_attr_server_monitor_pending.attr, + &dev_attr_client_monitor_pending.attr, + &dev_attr_server_monitor_latency.attr, + &dev_attr_client_monitor_latency.attr, + &dev_attr_server_monitor_conn_id.attr, + &dev_attr_client_monitor_conn_id.attr, + NULL +}; +ATTRIBUTE_GROUPS(vmbus_dev_monitor); + /* * vmbus_uevent - add uevent for our device * @@ -1537,19 +1546,30 @@ static struct attribute *vmbus_chan_attrs[] = { &chan_attr_read_avail.attr, &chan_attr_write_avail.attr, &chan_attr_cpu.attr, - &chan_attr_pending.attr, - &chan_attr_latency.attr, &chan_attr_interrupts.attr, &chan_attr_events.attr, &chan_attr_intr_in_full.attr, &chan_attr_intr_out_empty.attr, &chan_attr_out_full_first.attr, &chan_attr_out_full_total.attr, - &chan_attr_monitor_id.attr, &chan_attr_subchannel_id.attr, NULL }; +/* Set up per channel monitor page attributes. These attributes are used only by + * channels that use the monitor page mechanism. + */ +static struct attribute *vmbus_chan_monitor_attrs[] = { + &chan_attr_pending.attr, + &chan_attr_latency.attr, + &chan_attr_monitor_id.attr, + NULL +}; + +static struct attribute_group vmbus_chan_monitor_attr_group = { + .attrs = vmbus_chan_monitor_attrs, +}; + static struct kobj_type vmbus_chan_ktype = { .sysfs_ops = &vmbus_chan_sysfs_ops, .release = vmbus_chan_release, @@ -1571,6 +1591,15 @@ int vmbus_add_channel_kobj(struct hv_device *dev, struct vmbus_channel *channel) if (ret) return ret; + if (channel->offermsg.monitor_allocated) { + ret = sysfs_create_group(kobj, &vmbus_chan_monitor_attr_group); + if (ret) { + pr_err("Unable to set up monitor page sysfs files"); + kobject_put(kobj); + return ret; + } + } + kobject_uevent(kobj, KOBJ_ADD); return 0; @@ -1615,6 +1644,9 @@ int vmbus_device_register(struct hv_device *child_device_obj) child_device_obj->device.parent = &hv_acpi_dev->dev; child_device_obj->device.release = vmbus_device_release; + if (child_device_obj->channel->offermsg.monitor_allocated) + child_device_obj->device.groups = vmbus_dev_monitor_groups; + /* * Register with the LDM. This will kick off the driver/device * binding...which will eventually call vmbus_match() and vmbus_probe() -- 2.17.1
